W3C

PROV-DM: The PROV Data Model

working towards WD6

W3C WorkingEditor's Draft 0308 May 2012

This version:
http://www.w3.org/TR/2012/WD-prov-dm-20120503/http://dvcs.w3.org/hg/prov/raw-file/default/model/prov-dm.html
Latest published version:
http://www.w3.org/TR/prov-dm/
Latest editor's draft:
http://dvcs.w3.org/hg/prov/raw-file/default/model/prov-dm.html
Previous version:
http://www.w3.org/TR/2012/WD-prov-dm-20120202/http://www.w3.org/TR/2012/WD-prov-dm-20120503/
Editors:
Luc Moreau, University of Southampton
Paolo Missier, Newcastle University
Contributors:Authors:
Khalid Belhajjame, University of Manchester
Reza B'Far, Oracle Corporation
Stephen Cresswell, legislation.gov.uk
Yolanda Gil, Invited Expert
Paul Groth, VU University of Amsterdam
Graham Klyne, University of Oxford
Jim McCusker, Rensselaer Polytechnic Institute
Simon Miles, Invited Expert
James Myers, Rensselaer Polytechnic Institute
Satya Sahoo, Case Western Reserve University
Curt Tilmes, National Aeronautics and Space Administration

Abstract

PROV-DM, the PROV data model, is a data model for provenance that describes the entities, people and activities involved in producing a piece of data or thing. PROV-DM is structured in six components, dealing with: (1) entities and activities, and the time at which they were created, used, or ended; (2) agents bearing responsibility for entities that were generated and activities that happened; (3) derivations of entities from entities; (4) properties to link entities that refer to the same thing; (5) collections forming a logical structure for its members; (6) a simple annotation mechanism.

This document introduces the provenance concepts found in PROV and defines PROV-DM types and relations. PROV data model is domain-agnostic, but is equipped with extensibility points allowing domain-specific information to be included.

Two further documents complete the specification of PROV-DM. First, a companion document specifies the set of constraints that provenance descriptions should follow. Second, a separate document describes a provenance notation for expressing instances of provenance for human consumption; this notation is used in examples in this document.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

PROV Family of Specifications

This document is part of the PROV family of specifications, a set of specifications defining various aspects that are necessary to achieve the vision of inter-operable interchange of provenance information in heterogeneous environments such as the Web. The specifications are:

How to read the PROV Family of Specifications

Fourth Public Working Draft

This is the fourth public release of the PROV-DM document. Following feedback, the Working Group has decided to reorganize this document substantially, separating the data model from its contraints and the notation used to illustrate it. The PROV-DM release is synchronized with the release of the PROV-O, PROV-PRIMER, PROV-N, and PROV-CONSTRAINTS documents. We are now clarifying the entry path to the PROV family of specifications.

This document was published by the Provenance Working Group as a Workingan Editor's Draft. This document is intended to become a W3C Recommendation. If you wish to make comments regarding this document, please send them to public-prov-wg@w3.org (subscribe, archives). All feedback is welcome.

Publication as a Workingan Editor's Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

Table of Contents

1. Introduction

For the purpose of this specification, provenance is defined as a record that describes the people, institutions, entities, and activities involved in producing, influencing, or delivering a piece of data or a thing. In particular, the provenance of information is crucial in deciding whether information is to be trusted, how it should be integrated with other diverse information sources, and how to give credit to its originators when reusing it. In an open and inclusive environment such as the Web, where users find information that is often contradictory or questionable, provenance can help those users to make trust judgements.

We consider a core data model for provenance that allows domain and application specific representations of provenance to be translated into such a data model and interchanged between systems. Thus, heterogeneous systems can export their native provenance into such a core data model, and applications that need to make sense of provenance in heterogeneous systems can then import it, process it, and reason over it.

A set of specifications, referred to as the PROV family of specifications, define the various aspects that are necessary to achieve this vision in an interoperable way:

The PROV data model is a domain-agnostic model, but with clear extensibility points allowing further domain-specific and application-specific extensions to be defined. The PROV data model is structured according to six components covering various aspects of provenance:

This specification presents the key concepts of the PROV Data Model, and provenance types and relations, without specific concern for how they are applied. With these, it becomes possible to write useful provenance descriptions, and publish or embed them along side the data they relate to.

However, if something about which provenance is expressed is subject to change, then it is challenging to express its provenance precisely (e.g. the data from which a daily weather report is derived changes from day to day). To address this challenge, a refinement is proposed to enrich simple provenance, with extra descriptions that help qualify the specific subject of provenance and provenance itself, with attributes and temporal information, intended to satisfy a comprehensive set of constraints. These aspects are covered in the companion specification [PROV-CONSTRAINTS].

1.1 Structure of this Document

Section 2 provides starting points for the PROV Data Model, listing a set of types and relations, which allows users to make initial provenance descriptions.

Section 3 illustrates how the PROV data model can be used to express the provenance of a report published on the Web.

Section 4 provides the definitions of PROV concepts, structured according to six components.

Section 5 summarizes PROV-DM extensibility points.

Section 6 introduces the idea that constraints can be applied to the PROV data model to refine provenance descriptions; these are covered in the companion specification [PROV-CONSTRAINTS].

1.2 Notational Conventions

The key words "must", "must not", "required", "shall", "shall not", "should", "should not", "recommended", "may", and "optional" in this document are to be interpreted as described in [RFC2119].

The following namespaces prefixes are used throughout this document.

Table 1: Prefix and Namespaces used in this specification
prefixnamespace uri definition
provhttp://www.w3.org/ns/prov#The PROV namespace (see Section 4.7.1)
xsdhttp://www.w3.org/2000/10/XMLSchema#XML Schema Namespace [XMLSCHEMA-2]
rdfhttp://www.w3.org/1999/02/22-rdf-syntax-ns#The RDF namespace [RDF-CONCEPTS]
(others)(various)All other namespace prefixes are used in examples only.
In particular, URIs starting with "http://example.com" represent
some application-dependent URI [URI]

2. PROV Starting Points

This section introduces provenance concepts with informal descriptions and illustrative examples. Since PROV-DM is a conceptual data model, Section 2.5 maps the concepts to various types and relations, which are illustrated graphically in a simplified UML diagram in Figure 1. Section 2.6 then summarizes the PROV notation allowing instances of PROV-DM to be written down.

2.1 Entity and Activity

Things we want to describe the provenance of are called entities in PROV. The term "things" encompasses a broad diversity of notions, including digital objects such as a file or web page, physical things such as a building or a printed book, or a car as well as abstract concepts and ideas.

An entity is a physical, digital, conceptual, or other kind of thing; entities may be real or imaginary.

An entity may be the document at URI http://www.bbc.co.uk/news/science-environment-17526723, a file in a file system, a car, or an idea.

An activity is something that occurs over a period of time and acts upon or with entities; it may include consuming, processing, transforming, modifying, relocating, using, generating, or being associated with entities. Activities that operate on digital entities may for example move, copy, or duplicate them.

An activity may be the publishing of a document on the Web, sending a twitter message, extracting metadata embedded in a file, driving a car from Boston to Cambridge, assembling a data set based on a set of measurements, performing a statistical analysis over a data set, sorting news items according to some criteria, running a SPARQL query over a triple store, or editing a file.

2.2 Generation, Usage, Derivation

Activities and entities are associated with each other in two different ways: activities utilize entities and activities produce entities. The act of utilizing or producing an entity may have a duration. The term 'generation' refers to the completion of the act of producing; likewise, the term 'usage' refers to the beginning of the act of utilizing entities. Thus, we define the following notions of generation and usage.

Generation is the completion of production of a new entity by an activity. This entity did not exist before generation and becomes available for usage after this generation.

Usage is the beginning of utilizing an entity by an activity. Before usage, the activity had not begun to utilize this entity and could not have been affected by the entity.

Examples of generation are the completed creation of a file by a program, the completed creation of a linked data set, and the completed publication of a new version of a document.

Usage examples include a procedure beginning to consume an argument, a service starting to read a value on a port, a program beginning to read a configuration file, or the point at which an ingredient, such as eggs, is being added in a baking activity. Usage may entirely consume an entity (e.g. eggs are no longer available after being added to the mix); in contrast, the same entity may be used multiple times, possibly by different activities (e.g. a file on a file system can be read indefinitely).

Activities utilize entities and producer entities. In some cases, utilizing an entity influences the creation of another in some way. This notion is captured by derivations, defined as follows.

A derivation is a transformation of an entity into another, a construction of an entity into another, or an update of an entity, resulting in a new one.

Examples of derivation include the transformation of a relational table into a linked data set, the transformation of a canvas into a painting, the transportation of a work of art from London to New York, and a physical transformation such as the melting of ice into water.

2.3 Agents, Attribution, Association, and Responsibility

The motivation for introducing agents in the model is to express the agent's responsibility for activities that happened and entities that were generated.

An agent is something that bears some form of responsibility for an activity taking place or for the existence of an entity. An agent may be a particular type of entity. This means that the model can be used to express provenance of the agents themselves.

Software for checking the use of grammar in a document may be defined as an agent of a document preparation activity, and at the same time one can describe its provenance, including for instance the vendor and the version history. A site selling books on the Web, the services involved in the processing of orders, and the companies hosting them are also agents.

Agents may adopt sets of actions or steps to achieve their goals. This is captured by the notion of plan.

A plan is an entity that represents a set of actions or steps intended by one or more agents to achieve some goals. There exist no prescriptive requirement on the nature of plans, their representation, the actions or steps they consist of, or their intended goals. Since plans may evolve over time, it may become necessary to track their provenance, so plans themselves are entities. Representing the plan explicitly in the provenance can be useful for various tasks: for example, to validate the execution as represented in the provenance record, to manage expectation failures, or to provide explanations.

A plan can be a blog post tutorial for how to set up a web server, a list of instructions for a micro-processor execution, a cook's written recipe for a chocolate cake, or a workflow for a scientific experiment.

Agents can be related to entities, activities, and other agents.

Attribution is the ascribing of an entity to an agent.

A blog post can be attributed to an author, a mobile phone to its manufacturer.

Agents are defined as having some kind of responsibility for activities. In some cases, those activities reflect the execution of a plan that was designed in advance to guide the execution. Thus, a plan may also be linked to an activity.

An activity association is an assignment of responsibility to an agent for an activity, indicating that the agent had a role in the activity. It further allows for a plan to be specified, which is the plan intended by the agent to achieve some goals in the context of this activity.

Examples of association between an activity and an agent are:

  • creation of a web page under the guidance of a designer;
  • various forms of participation in a panel discussion, including audience member, panelist, or panel chair;
  • a public event, sponsored by a company, and hosted by a museum;
  • an XSLT transform launched by a user based on an XSL style sheet (a plan).

Responsibility is the fact that an agent is accountable for the actions of a "subordinate" agent, in the context of an activity. The nature of this relation is intended to be broad, including delegation or contractual relation.

A student publishing a web page describing an academic department could result in both the student and the department being agents associated with the activity, and it may not matter which student published a web page but it matters a lot that the department told the student to put up the web page.

2.4 Further Entities: Collections and Accounts

There are two further types of entities, collections and accounts, which are now introduced.

A collection is an entity that provides a structure to some constituents, which are themselves entities. These constituents are said to be member of the collections. This concept allows for the provenance of the collection itself to be expressed in addition to that of the members. Many different types of collections exist, such as a set, dictionaries, or lists, all of which involve a membership relationship between the constituents and the collection.

An example of collection is an archive of documents. Each document has its own provenance, but the archive itself also has some provenance: who maintained it, which documents it contained at which point in time, how it was assembled, etc.

An account is an entity that contains a bundle of provenance descriptions. Making an account an entity allows for provenance of provenance to be expressed.

For users to decide whether they can place their trust in a resource, they may want to analyze the resource's provenance, but also determine who its provenance is attributed to, and when it was generated. In other words, users need to be able to determine the provenance of provenance. Hence, provenance is also regarded as an entity (of type Account), by which provenance of provenance can then be expressed.

2.5 Simplified Overview Diagram

So far, we have introduced a series of concepts underpinning provenance. PROV-DM is a conceptual data model consisting of types and relations between these. Table 2 shows how provenance concepts can be mapped to types and relations in PROV-DM: the first column lists concepts introduced in this section, the second column indicates whether a concept maps to a type or a relation, whereas the third column contains the corresponding name. Names of relations have a verbal form in the past tense to express what happened in the past, as opposed to what may or will happen.

Table 2: Mapping of Provenance concepts to types and relations
PROV ConceptsPROV-DM types or relationsName
EntityPROV-DM Typesentity
Activityactivity
Agentagent
GenerationPROV-DM RelationswasGeneratedBy
Usageused
AttributionwasAttributedTo
AssociationwasAssociatedWith
ResponsibilityactedOnBehalfOf
DerivationwasDerivedFrom

Figure 1 illustrates the three types (entity, activity, and agent) and how they relate to each other. At this stage, all relations are shown to be binary. Definitions of Section 4 reveal that some relations, while involving two primary elements, are n-ary.

Simplified  Overview of PROV-DM
Figure 1: Simplified Overview of PROV-DM

Figure 1 is not intended to be complete: it only illustrates types and relations introduced in this section (Section 2), exploited in the example discussed in Section 3, and explained in detail in Section 4. Names of relations depicted in Figure 1 are listed in the third column of Table 2. These names are part of a textual notation to write instances of the PROV data model, which we introduce in the next section.

2.6 PROV-N: The Provenance Notation

To illustrate the application of PROV concepts to a concrete example (see Section 3) and to provide examples of concepts (see Section 4), we introduce PROV-N, a notation for writing instances of the PROV data model. For full details, the reader is referred to the companion specification [PROV-N]. PROV-N is a notation aimed at human consumption, with the following characteristics:

An activity with identifier a1 and an attribute type with value createFile.

activity(a1, [prov:type="createFile"])
Two entities with identifiers e1 and e2.
entity(e1)
entity(e2)
The activity a1 used e1, and e2 was generated by a1.
used(a1,e1)
wasGeneratedBy(e2,a1)
The same description, but with an explicit identifier u1 for the usage, and the syntactic marker - to mark the absence of identifier in the generation.
used(u1,a1,e1)
wasGeneratedBy(-,e2,a1)

3. Illustration of PROV-DM by an Example

Section 2 has introduced some provenance concepts, and how they are expressed as types or relations in the PROV data model. The purpose of this section is to put these concepts into practice in order to express the provenance of some document published on the Web. With this realistic example, PROV concepts are composed together, and a graphical illustration shows a provenance description forming a directed graph, rooted at the entity we want to explain the provenance of, and pointing to the entities, activities, and agents it depended on. This example also shows that, sometimes, multiple provenance descriptions about the same entity can co-exist, which then justifies the need for provenance of provenance.

In this example, we consider one of the many documents published by the World Wide Web Consortium, and describe its provenance. Specifically, we consider the document identified by http://www.w3.org/TR/2011/WD-prov-dm-20111215. Its provenance can be expressed from several perspectives: first, provenance can take the authors' viewpoint; second, it can be concerned with the W3C process. Then, attribution of these two provenance descriptions is provided.

3.1 The Authors View

Description: A document is edited by some editor, using contributions from various contributors.

In this perspective, provenance of the document http://www.w3.org/TR/2011/WD-prov-dm-20111215 is concerned with the editing activity as perceived by authors. This kind of information could be used by authors in their CV or in a narrative about this document.

We paraphrase some PROV-DM descriptions, express them with the PROV-N notation, and then depict them with a graphical illustration (see Figure 1). Full details of the provenance record can be found here.

Provenance descriptions can be illustrated graphically. The illustration is not intended to represent all the details of the model, but it is intended to show the essence of a set of provenance descriptions. Therefore, it should not be seen as an alternate notation for expressing provenance.

The graphical illustration takes the form of a graph. Entities, activities and agents are represented as nodes, with oval, rectangular, and pentagonal shapes, respectively. Usage, Generation, Derivation, and Association are represented as directed edges.

Entities are laid out according to the ordering of their generation. We endeavor to show time progressing from left to right. This means that edges for Usage, Generation, Derivation, Association typically point leftwards

Provenance of a Document (1)
Figure 2: Provenance of a Document (1)

3.2 The Process View

Description: The World Wide Web Consortium publishes documents according to its publication policy. Working drafts are published regularly to reflect the work accomplished by working groups. Every publication of a working draft must be preceded by a "publication request" to the Webmaster. The very first version of a document must also be preceded by a "transition request" to be approved by the W3C director. All working drafts are made available at a unique URI. In this scenario, we consider two successive versions of a given document, the policy according to which they were published, and the associated requests.

We describe the kind of provenance record that the WWW Consortium could keep for auditors to check that due processes are followed. All entities involved in this example are Web resources, with well defined URIs (some of which refer archived email messages, available to W3C Members).

We now paraphrase some PROV descriptions, and express them with the PROV-N notation, and then depict them with a graphical illustration (see Figure 2). Full details of the provenance record can be found here.

Provenance of a Document (2)
Figure 3: Provenance of a Document (2)

This simple example has shown a variety of PROV concepts, such as Entity, Agent, Activity, Usage, Generation, Derivation, and Association. In this example, it happens that all entities were already Web resources, with readily available URIs, which we used. We note that some of the resources are public, whereas others have restricted access: provenance statements only make use of their identifiers. If identifiers do not pre-exist, e.g. for activities, then they can be generated, for instance ex:act2, occurring in the namespace identified by prefix ex. We note that the URI scheme developed by W3C is particularly suited for expressing provenance of these documents, since each URI denotes a specific version of a document. It then becomes easy to relate the various versions with PROV-DM relations. We note that an Association is a ternary relation (represented by a multi-edge labeled wasAssociatedWith) from an activity to an agent and a plan.

3.3 Attribution of Provenance

The two previous sections provide two different perspectives on the provenance of a document By design, the PROV approach allows for the provenance of a subject to be provided by multiple sources. For users to decide whether they can place their trust in the document, they may want to analyze its provenance, but also determine who the provenance is attributed to, and when it was generated, etc. In other words, we need to be able to express the provenance of provenance.

No new mechanism is required to support this requirement. PROV-DM makes the assumption that provenance statements have been bundled up, and named, by some mechanism outside the scope of PROV-DM. For instance, in this case, provenance statements were put in a file and exposed on the Web, respectively at ex:w3c-publication1.pn and ex:w3c-publication3.pn. To express their respective provenance, these resources must be seen as entities, and all the constructs of PROV-DM are now available to characterize their provenance. In the example below, ex:w3c-publication1.pn is attributed to the agent w3:Consortium, whereas ex:w3c-publication3.pn to ex:Simon.

entity(ex:w3c-publication1.pn, [prov:type="prov:Account" %% xsd:QName ])
wasAttributedTo(ex:w3c-publication1.pn, w3:Consortium)

entity(ex:w3c-publication3.pn, [prov:type="prov:Account" %% xsd:QName ])
wasAttributedTo(ex:w3c-publication3.pn, ex:Simon)

4. PROV-DM Types and Relations

Provenance concepts, expressed as PROV-DM types and relations, are structured according to six components that are introduced in this section. Components and their dependencies are illustrated in Figure 4. A component that relies on concepts defined in another also sits above it in this figure. PROV-DM consists of the following components.

PROV-DM Components collections alternate annotations activities/entities derivations agents/responsibility
Figure 4: PROV-DM Components

While not all PROV-DM relations are binary, they all involve two primary elements. Hence, Table 3 indexes all relations according to their two primary elements. The table adopts the same color scheme as Figure 4, allowing components to be readily identified. Note that for simplicity, this table does not include collection-oriented relations.

Table 3: PROV-DM Relations At a Glance
EntityActivityAgentNote
EntitywasGeneratedBy
wasInvalidatedBy
wasAttributedTohasAnnotation
ActivitywasStartedByActivity
wasInformedBy
wasAssociatedWithhasAnnotation
AgentactedOnBehalfOfhasAnnotation
NotehasAnnotation

Table 4 is a complete index of all the types and relations of PROV-DM, color-coded according to the component they belong to. In the first column, concept names link to their informal definition, whereas, in the second column, representations link to the information used to represent the concept.

Table 4: PROV-DM Types and Relations
Type or Relation NameRepresentation in the PROV-N notation
Entityentity(id, [ attr1=val1, ...])
Activityactivity(id, st, et, [ attr1=val1, ...])
GenerationwasGeneratedBy(id,e,a,t,attrs)
Usageused(id,a,e,t,attrs)
StartwasStartedBy(id,a,e,t,attrs)
EndwasEndedBy(id,a,e,t,attrs)
InvalidationwasInvalidatedBy(id,e,a,t,attrs)
CommunicationwasInformedBy(id,a2,a1,attrs)
Start by ActivitywasStartedByActivity(id, a2, a1, attrs)
Agentagent(id, [ attr1=val1, ...])
AttributionwasAttributedTo(id,e,ag,attr)
AssociationwasAssociatedWith(id,a,ag,pl,attrs)
ResponsibilityactedOnBehalfOf(id,ag2,ag1,a,attrs)
DerivationwasDerivedFrom(id, e2, e1, a, g2, u1, attrs)
RevisionwasRevisionOf(id,e2,e1,ag,attrs)wasRevisionOf(id, e2, e1, a, g2, u1, attrs)
QuotationwasQuotedFrom(id,e2,e1,ag2,ag1,attrs)wasQuotedFrom(id, e2, e1, a, g2, u1, attrs)
Original SourcehadOriginalSource(id,e2,e1,attrs)hadOriginalSource(id, e2, e1, a, g2, u1, attrs)
TracetracedTo(id,e2,e1,attrs)
AlternatealternateOf(alt1, alt2)
SpecializationspecializationOf(sub, super)
CollectionCollection
DictionaryDictionary
InsertionderivedByInsertionFrom(id, c2, c1, {(key_1, e_1), ..., (key_n, e_n)}, attrs)
RemovalderivedByRemovalFrom(id, c2, c1, {key_1, ... key_n}, attrs)
MembershipmemberOf(c, {(key_1, e_1), ..., (key_n, e_n)})
Notenote(id, [ attr1=val1, ...])
AnnotationhasAnnotation(r,n)

In the rest of the section, each type and relation is defined informally, followed by a summary of the information used to represent the concept, and illustrated with PROV-N examples.

4.1 Component 1: Entities and Activities

The first component of PROV-DM is concerned with entities and activities, and their interrelations: Usage, Generation, Start, End, Invalidation, Communication, and Start by Activity. Figure 5 uses UML to depict the first component, with two classes and binary associations between them. Associations are not just binary: indeed, Usage, Generation, Start, End also include time attributes.

entities and activities
Figure 5: Entities and Activities Component Overview

4.1.1 Entity

An entity is a physical, digital, conceptual, or other kind of thing; entities may be real or imaginary.

An entity, written entity(id, [attr1=val1, ...]) in PROV-N, has:
  • id: an identifier for an entity;
  • attributes: an optional set of attribute-value pairs ((attr1, val1), ...) representing additional information about this entity.

The following expression

entity(tr:WD-prov-dm-20111215, [ prov:type="document", ex:version="2" ])
states the existence of an entity, denoted by identifier tr:WD-prov-dm-20111215, with type document and version number 2. The attribute ex:version is application specific, whereas the attribute type (see Section 4.7.4.4) is reserved in the PROV namespace.

4.1.2 Activity

An activity is something that occurs over a period of time and acts upon or with entities; it may include consuming, processing, transforming, modifying, relocating, using, generating, or being associated with entities.

An activity, written activity(id, st, et, [attr1=val1, ...]) in PROV-N, has:
  • id: an identifier for an activity;
  • startTime: an optional time (st) for the start of the activity;
  • endTime: an optional time (et) for the end of the activity;
  • attributes: an optional set of attribute-value pairs ((attr1, val1), ...) representing additional information about this activity.

The following expression

activity(a1,2011-11-16T16:05:00,2011-11-16T16:06:00,
        [ex:host="server.example.org",prov:type="ex:edit" %% xsd:QName])

states the existence of an activity with identifier a1, start time 2011-11-16T16:05:00, and end time 2011-11-16T16:06:00, running on host server.example.org, and of type edit. The attribute host is application specific (declared in some namespace with prefix ex). The attribute type is a reserved attribute of PROV-DM, allowing for sub-typing to be expressed (see Section 4.7.4.4).

Further considerations:

  • An activity is not an entity. This distinction is similar to the distinction between 'continuant' and 'occurrent' in logic [Logic].

4.1.3 Generation

Generation is the completion of production of a new entity by an activity. This entity did not exist before generation and becomes available for usage after this generation.

Generation, written wasGeneratedBy(id,e,a,t,attrs) in PROV-N, has:
  • id: an optional identifier for a generation;
  • entity: an identifier (e) for a created entity;
  • activity: an optional identifier (a) for the activity that creates the entity;
  • time: an optional "generation time" (t), the time at which the entity was completely created;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this generation.

While each of activity, time, and attributes is optional, at least one of them must be present.

The following expressions

  wasGeneratedBy(e1,a1, 2001-10-26T21:32:52, [ex:port="p1"])
  wasGeneratedBy(e2,a1, 2001-10-26T10:00:00, [ex:port="p2"])

state the existence of two generations (with respective times 2001-10-26T21:32:52 and 2001-10-26T10:00:00), at which new entities, identified by e1 and e2, are created by an activity, identified by a1. The first one is available on port p1, whereas the other is available on port p2. The semantics of port are application specific.

In some cases, we may want to record the time at which an entity was generated without having to specify the activity that generated it. To support this requirement, the activity element in generation is optional. Hence, the following expression indicates the time at which an entity is generated, without naming the activity that did it.

  wasGeneratedBy(e,-,2001-10-26T21:32:52)

4.1.4 Usage

Usage is the beginning of utilizing an entity by an activity. Before usage, the activity had not begun to utilize this entity and could not have been affected by the entity.

Usage, written used(id,a,e,t,attrs) in PROV-N, has:
  • id: an optional identifier for a usage;
  • activity: an identifier (a) for the consuming activity;
  • entity: an identifier (e) for the consumed entity;
  • time: an optional "usage time" (t), the time at which the entity started to be used;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this usage.

A reference to a given entity may appear in multiple usages that share a given activity identifier.

The following usages

  used(a1,e1,2011-11-16T16:00:00,[ex:parameter="p1"])
  used(a1,e2,2011-11-16T16:00:01,[ex:parameter="p2"])

state that the activity identified by a1 used two entities identified by e1 and e2, at times 2011-11-16T16:00:00 and 2011-11-16T16:00:01, respectively; the first one was found as the value of parameter p1, whereas the second was found as value of parameter p2. The semantics of parameter is application specific.

4.1.5 Start

Start is when an activity is deemed to have started. The activity did not exist before its start. Any usage or generation involving an activity follows the activity's start. A start may refer to an entity, known as trigger, that initiated the activity.

An activity start, written wasStartedBy(id,a,e,t,attrs) in PROV-N, has:
  • id: an optional identifier for the activity start;
  • activity: an identifier (a) for the started activity;
  • trigger: an optional identifier (e) for the entity triggering the activity;
  • time: the optional time (t) at which the activity was started;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this activity start.

The following example contains the description of an activity a1 (a discussion), which was started at a specific time, and was triggered by an email message e1.

entity(e1,[prov:type="email message"])
activity(a1,[prov:type="Discuss"])
wasStartedBy(a1,e1,2011-11-16T16:05:00)
Furthermore, if the message is also an input to the activity, this can be described as follows:
used(a1,e1,-)

In the following example, a race is started by a bang, and responsibility for this trigger is attributed to an agent ex:Bob.

activity(ex:foot_race)
wasStartedBy(ex:foot_race,ex:bang,2012-03-09T08:05:08-05:00)
entity(ex:bang)
agent(ex:Bob)
wasAttributedTo(ex:bang,ex:Bob)

The relations wasStartedBy and used are orthogonal, and thus need to be expressed independently, according to the situation being described.

4.1.6 End

End is when an activity is deemed to have ended. The activity no longer exists after its end. Any usage, generation, or invalidation involving an activity precedes the activity's end. An end may refer to an entity, known as trigger, that terminated the activity.

An activity end, written wasEndedBy(id,a,e,t,attrs) in PROV-N, has:
  • id: an optional identifier for the activity end;
  • activity: an identifier (a) for the ended activity;
  • trigger: an optional identifier (e) for the entity triggering the activity ending;
  • time: the optional time (t) at which the activity was ended;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this activity end.

The following example is a description of an activity a1 (editing) that was ended following an approval document e1.

entity(e1,[prov:type="approval document"])
activity(a1,[prov:type="Editing"])
wasEndedBy(a1,e1)

4.1.7 Invalidation

Invalidation is the start of the destruction, cessation, or expiry of an existing entity by an activity. The entity is no longer available for use after invalidation. Any generation or usage of an entity precedes its invalidation.

Entities have a duration. Generation marks the beginning of an entity. An entity's lifetime can end for different reasons:

  • an entity was destroyed: e.g. a painting was destroyed by fire; a Web page is taken out of a site;
  • an entity was consumed: e.g. Bob ate all his soup, Alice ran out of gas when driving to work;
  • an entity expires: e.g. a "buy one beer, get one free" offer is valid during happy hour (7-8pm);
  • an entity is time limited: e.g. the BBC news site on April 3rd, 2012;
  • an entity attribute is changing: e.g. the traffic light changed from green to red.

In the first two cases, the entity has physically disappeared after its termination: there is no more soup, or painting. In the last two cases, there may be an "offer voucher" that still exists, but it is no longer valid; likewise, on April 4th, the BBC news site still exists but it is not the same entity as BBC news Web site on April 3rd; or the traffic light became red and therefore is regarded as a different entity to the green light.

Invalidation, written wasInvalidatedBy(id,e,a,t,attrs) in PROV-N, has:
  • id: an optional identifier for a invalidation;
  • entity: an identifier for the invalidated entity;
  • activity: an optional identifier for the activity that invalidated the entity;
  • time: an optional "invalidation time", the time at which the entity began to be invalidated;
  • attributes: an optional set of attribute-value pairs representing additional information about this invalidation.

While each of activity, time, and attributes is optional, at least one of them must be present.

The Painter, a Picasso painting, is known to have been destroyed in a plane accident.

entity(ex:The-Painter)
agent(ex:Picasso)
wasAttributedTo(ex:The-Painter, ex:Picasso)
activity(ex:crash)
wasInvalidatedBy(ex:The-Painter, ex:crash, 1998-09-02, [ex:circumstances="plane accident"])

The BBC news home page on 2012-04-03 ex:bbcNews2012-04-03 contained a reference to a given news item bbc:news/uk-17595024, but the BBC news home page on the next day did not.

entity(ex:bbcNews2012-04-03)
memberOf(ex:bbcNews2012-04-03,{("item1", bbc:news/uk-17595024)})
wasGeneratedBy  (ex:bbcNews2012-04-03,-,2012-04-03T00:00:01)
wasInvalidatedBy(ex:bbcNews2012-04-03,-,2012-04-03T23:59:59)
We refer to example anexample-specialization for further descriptions of the BBC Web site, and to Section Membership for a description of the relation memberOf.

In this example, the "buy one beer, get one free" offer expired at the end of the happy hour.

entity(buy_one_beer_get_one_free_offer_during_happy_hour)
wasAttributedTo(proprietor)
wasInvalidatedBy(buy_one_beer_get_one_free_offer_during_happy_hour,
                 -,2012-03-10T18:00:00)

In contrast, in the following descriptions, Bob redeemed the offer 45 minutes before it expired, and got two beers.

entity(buy_one_beer_get_one_free_offer_during_happy_hour)
wasAttributedTo(proprietor)
activity(redeemOffer)
entity(twoBeers)

wasAssociatedWith(redeemOffer,bob)
used(buy_one_beer_get_one_free_offer_during_happy_hour,
     redeemOffer, 2012-03-10T17:15:00)
wasInvalidatedBy(buy_one_beer_get_one_free_offer_during_happy_hour,
                 redeemOffer, 2012-03-10T17:15:00)
wasGeneratedBy(twoBeers,redeemOffer)

We see that the offer was both used to be converted into twoBeers and invalidated by the redeemOffer activity: in other words, the combined usage and invalidation indicate consumption of the offer.

4.1.8 Communication

Communication is the exchange of an entity by two activities, one activity using the entity generated by the other.

A communication implies that activity a2 is dependent on another a1, by way of some unspecified entity that is generated by a1 and used by a2.

A communication, written as wasInformedBy(id,a2,a1,attrs) in PROV-N, has:
  • id: an optional identifier identifying the relation;
  • informed: the identifier (a2) of the informed activity;
  • informant: the identifier (a1) of the informant activity;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this communication.

Consider two activities a1 and a2, the former performed by a government agency, and the latter by a driver caught speeding.

activity(a1, [prov:type="traffic regulations enforcing"])
activity(a2, [prov:type="fine paying, check writing, and mailing"])
wasInformedBy(a2,a1)
The last line indicates that some implicit entity was generated by a1 and used by a2; this entity may be a traffic ticket that had a notice of fine, amount, and payment mailing details.

4.1.9 Start by Activity

Start by Activity is the start of an activity with an implicit trigger generated by another activity.

A start by activity, written as wasStartedByActivity(id, a2, a1, attrs) in PROV-N, has:
  • id: an optional identifier of the relation;
  • started: the identifier (a2) of the started activity;
  • starter: the identifier (a1) of the activity that started the other;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this start by activity.

Suppose activities a1 and a2 are computer processes that are executed on different hosts, and that a1 started a2. This can be expressed as in the following fragment:

activity(a1,t1,t2,[ex:host="server1.example.org",prov:type="workflow"])
activity(a2,t3,t4,[ex:host="server2.example.org",prov:type="subworkflow"])
wasStartedByActivity(a2,a1)
It is assumed that the activities a1 and a2 are of type "workflow" and "subworkflow", respectively; the latter was started by the former.

4.2 Component 2: Agents and Responsibility

The second component of PROV-DM is concerned with agents and the notions of Attribution, Association, Responsibility, relating agents to entities, activities, and agents, respectively. Figure figure-component2 depicts the second component with four classes (Entity, Activity, Agent, and Plan) and associations between them. UML association classes are used to express n-ary relations.

agents and responsibilities
Figure 6: Agents and Responsibilities Component Overview

4.2.1 Agent

An agent is something that bears some form of responsibility for an activity taking place or for the existence of an entity.

An agent, written agent(id, [attr1=val1, ...]) in PROV-N, has:
  • id: an identifier for an agent;
  • attributes: a set of attribute-value pairs ((attr1, val1), ...) representing additional information about this agent.

It is useful to define some basic categories of agents from an interoperability perspective. There are three types of agents that are common across most anticipated domains of use; It is acknowledged that these types do not cover all kinds of agent.

  • SoftwareAgent
    A software agent is running software.

  • Organization
    Agents of type Organization are social or legal institutions such as companies, societies, etc.

  • Person
    Agents of type Person are people.

The following expression is about an agent identified by e1, which is a person, named Alice, with employee number 1234.

agent(e1, [ex:employee="1234", ex:name="Alice", prov:type="prov:Person" %% xsd:QName])

It is optional to specify the type of an agent. When present, it is expressed using the prov:type attribute.

4.2.2 Attribution

Attribution is the ascribing of an entity to an agent.

When an entity e is attributed to agent ag, entity e was generated by some unspecified activity that in turn was associated to agent ag. Thus, this relation is useful when the activity is not known, or irrelevant.

An attribution relation, written wasAttributedTo(id,e,ag,attrs) in PROV-N, has:
  • id: an optional identifier for the relation;
  • entity: an entity identifier (e);
  • agent: the identifier (ag) of the agent whom the entity is ascribed to;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this attribution.

Revisiting the example of Section 3.1, we can ascribe tr:WD-prov-dm-20111215 to some agents without an explicit activity. The reserved attribute role (see Section 4.7.4.3) allows for role of the agent in the attribution to be specified.

agent(ex:Paolo, [ prov:type="Person" ])
agent(ex:Simon, [ prov:type="Person" ])
entity(tr:WD-prov-dm-20111215, [ prov:type="process:RecsWD" %% xsd:QName ])
wasAttributedTo(tr:WD-prov-dm-20111215, ex:Paolo, [prov:role="editor"])
wasAttributedTo(tr:WD-prov-dm-20111215, ex:Simon, [prov:role="contributor"])

4.2.3 Association

An activity association is an assignment of responsibility to an agent for an activity, indicating that the agent had a role in the activity. It further allows for a plan to be specified, which is the plan intended by the agent to achieve some goals in the context of this activity.

A plan is an entity that represents a set of actions or steps intended by one or more agents to achieve some goals.

An activity association, written wasAssociatedWith(id,a,ag,pl,attrs) in PROV-N, has:
  • id: an optional identifier for the association between an activity and an agent;
  • activity: an identifier (a) for the activity;
  • agent: an optional identifier (ag) for the agent associated with the activity;
  • plan: an optional identifier (pl) for the plan adopted by the agent in the context of this activity;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this association of this activity with this agent.

In the following example, a designer and an operator agents are associated with an activity. The designer's goals are achieved by a workflow ex:wf, described as an an entity of type plan.

activity(ex:a, [prov:type="workflow execution"])
agent(ex:ag1, [prov:type="operator"])
agent(ex:ag2, [prov:type="designer"])
wasAssociatedWith(ex:a, ex:ag1, -, [prov:role="loggedInUser", ex:how="webapp"])
wasAssociatedWith(ex:a, ex:ag2, ex:wf,[prov:role="designer", ex:context="project1"])
entity(ex:wf, [prov:type="prov:Plan" %% xsd:QName, ex:label="Workflow 1", 
              ex:url="http://example.org/workflow1.bpel" %% xsd:anyURI])
Since the workflow ex:wf is itself an entity, its provenance can also be expressed in PROV-DM: it can be generated by some activity and derived from other entities, for instance.

In some cases, one wants to indicate a plan was followed, without having to specify which agent was involved.

activity(ex:a,[prov:type="workflow execution"])
wasAssociatedWith(ex:a,-,ex:wf)
entity(ex:wf,[prov:type="prov:Plan"%% xsd:QName, ex:label="Workflow 1", 
              ex:url="http://example.org/workflow1.bpel" %% xsd:anyURI])
In this case, it is assumed that an agent exists, but it has not been specified.

4.2.4 Responsibility

Responsibility is the fact that an agent is accountable for the actions of a "subordinate" agent, in the context of an activity.

PROV offers a mild version of responsibility in the form of a relation to represent when an agent acted on another agent's behalf. So for example someone running a mail program, the program and the person are both agents of the activity; furthermore, the mail software agent is running on the person's behalf. In another example, the student acted on behalf of his supervisor, who acted on behalf of the department chair, who acted on behalf of the university; all those agents are responsible in some way for the activity that took place but we do not say explicitly who bears responsibility and to what degree.

A responsibility link, written actedOnBehalfOf(id,ag2,ag1,a,attrs) in PROV-N, has:
  • id: an optional identifier for the responsibility link between subordinate and responsible;
  • subordinate: an identifier (ag2) for the agent associated with an activity, acting on behalf of the responsible agent;
  • responsible: an identifier (ag1) for the agent, on behalf of which the subordinate agent acted;
  • activity: an optional identifier (a) of an activity for which the responsibility link holds;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this responsibility link.

The following fragment describes three agents: a programmer, a researcher, and a funder. The programmer and researcher are associated with a workflow activity. The programmer acts on behalf of the researcher (delegation) encoding the commands specified by the researcher; the researcher acts on behalf of the funder, who has a contractual agreement with the researcher. The terms 'delegation' and 'contact' used in this example are domain specific.

activity(a,[prov:type="workflow"])
agent(ag1,[prov:type="programmer"])
agent(ag2,[prov:type="researcher"])
agent(ag3,[prov:type="funder"])
wasAssociatedWith(a,ag1,[prov:role="loggedInUser"])
wasAssociatedWith(a,ag2)
wasAssociatedWith(a,ag3)
actedOnBehalfOf(ag1,ag2,a,[prov:type="delegation"])
actedOnBehalfOf(ag2,ag3,a,[prov:type="contract"])

4.3 Component 3: Derivations

The third component of PROV-DM is concerned with derivations of entities from others, and derivation subtypes Revision, Quotation, Original Source, and Trace. Figure figure-component3 depicts the third component with three classes (Entity, Activity, and Agent) and associations between them. UML association classes express n-ary relations.

derivation
Figure 7: Derivation Component Overview

4.3.1 Derivation

A derivation is a transformation of an entity into another, a construction of an entity into another, or an update of an entity, resulting in a new one.

According to Section 2, for an entity to be transformed from, created from, or resulting from an update to another, there must be some underpinning activities performing the necessary actions resulting in such a derivation. A derivation can be described at various levels of precision. In its simplest form, derivation relates two entities. Optionally, attributes can be added to represent further information about the derivation. If the derivation is the result of a single known activity, then this activity can also be optionally expressed. To provide a completely accurate description of the derivation, the generation and usage of the generated and used entities, respectively, can be provided. Optional information such as activity, generation, and usage can be linked to derivations to aid analysis of provenance and to facilitate provenance-based reproducibility.

A derivation, written wasDerivedFrom(id, e2, e1, a, g2, u1, attrs) in PROV-N, has:
  • id: an optional identifier for a derivation;
  • generatedEntity: the identifier (ee) of the entity generated by the derivation;
  • usedEntity: the identifier (e1) of the entity used by the derivation;
  • activity: an optional identifier (a) for the activity using and generating the above entities;
  • generation: an optional identifier (g2) for the generation involving the generated entity (e2) and activity;
  • usage: an optional identifier (u1) for the usage involving the used entity (e1) and activity;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this derivation.

The following descriptions are about derivations between e2 and e1, but no information is provided as to the identity of the activity (and usage and generation) underpinning the derivation. In the second line, a type attribute is also provided.

wasDerivedFrom(e2, e1)
wasDerivedFrom(e2, e1, [prov:type="physical transform"])

The following description expresses that activity a, using the entity e1 according to usage u1, derived the entity e2 and generated it according to generation g2. It is followed by descriptions for generation g2 and usage u1.

wasDerivedFrom(e2, e1, a, g2, u1)
wasGeneratedBy(g2, e2, a, -)
used(u1, a, e1, -)

With such a comprehensive description of derivation, a program that analyzes provenance can identify the activity underpinning the derivation, it can identify how the original entity e1 was used by the activity (e.g. for instance, which argument it was passed as, if the activity is the result of a function invocation), and which output the derived entity e2 was obtained from (say, for a function returning multiple results).

4.3.2 Revision

A revision is a derivation that revises an entity into a revised version.

Deciding whether something is made available as a revision of something else usually involves an agent who takes responsibility for approving that the former is a due variant of the latter. The agent who is responsible for the revision may optionally be specified. Revision is a particular case of derivation of an entity into its revised version.

A revision relation, written wasRevisionOf(id,e2,e1,ag,attrs)wasRevisionOf(id, e2, e1, a, g2, u1, attrs) in PROV-N, has:

  • id: an optional identifier for the relation;
  • newer: the identifier (e2) of the revised entity;
  • older: the identifier (e1) of the older entity;
  • responsibilityactivity: an optional identifier (aga) for the agent who approved the neweractivity using and generating the above entities;
  • generation: an optional identifier (g2) for the generation involving the generated entity as a variant of the older; (e2) and activity;
  • usage: an optional identifier (u1) for the usage involving the used entity (e1) and activity;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this relation.

Revisiting the example of Section 3.2, we can now state that the report tr:WD-prov-dm-20111215 iswas a revision of the report tr:WD-prov-dm-20111018, approved by agent w3:Consortium.

entity(tr:WD-prov-dm-20111215, [ prov:type="process:RecsWD" %% xsd:QName ])
entity(tr:WD-prov-dm-20111018, [ prov:type="process:RecsWD" %% xsd:QName ])
wasRevisionOf(tr:WD-prov-dm-20111215, tr:WD-prov-dm-20111018, w3:Consortium)tr:WD-prov-dm-20111018)

4.3.3 Quotation

A quotation is the repeat of (some or all of) an entity, such as text or image, by someone other thanwho may or may not be its original author.

Quotation is a particular case of derivation in which entity e2 is derived from an original entity e1 by copying, or "quoting", some or all of it. A quotation relation, written wasQuotedFrom(id,e2,e1,ag2,ag1,attrs)wasQuotedFrom(id, e2, e1, a, g2, u1, attrs) in PROV-N, has:

  • id: an optional identifier for the relation;
  • quote: an identifier (e2) for the entity that represents the quote (the partial copy);
  • original: an identifier (e1) for the original entity being quoted;
  • quoterAgentactivity: an optional identifier (ag2a) for the agent who performs the quote; activity using and generating the above entities;
  • originalAgentgeneration: an optional identifier (ag1g2) for the agent to whom the originalgeneration involving the generated entity is attributed; (e2) and activity;
  • usage: an optional identifier (u1) for the usage involving the used entity (e1) and activity;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this relation.

The following paragraph is a quote from one of the author's blogs.

"During the workshop, it became clear to me that the consensus based models (which are often graphical in nature) can not only be formalized but also be directly connected to these database focused formalizations. I just needed to get over the differences in syntax. This could imply that we could have nice way to trace provenance across systems and through databases and be able to understand the mathematical properties of this interconnection."

If wp:thoughts-from-the-dagstuhl-principles-of-provenance-workshop/ denotes the original blog by agent ex:Paul, and dm:bl-dagstuhl denotes the above paragraph, then the following descriptions express that the above paragraph is copied by agent ex:Luc from a part of the blog, attributed to the agent ex:Paul.

entity(wp:thoughts-from-the-dagstuhl-principles-of-provenance-workshop/)
agent(ex:Luc)
agent(ex:Paul)
wasQuotedFrom(dm:bl-dagstuhl,wp:thoughts-from-the-dagstuhl-principles-of-provenance-workshop/,ex:Luc,ex:Paul)wasQuotedFrom(dm:bl-dagstuhl,wp:thoughts-from-the-dagstuhl-principles-of-provenance-workshop/)
wasAttributedTo(dm:bl-dagstuhl, ex:Luc)
wasAttributedTo(wp:thoughts-from-the-dagstuhl-principles-of-provenance-workshop/, ex:Paul)

4.3.4 Original Source

An original source refers to the source material that is closest to the person, information, period, or idea being studied.

An original source relation is a particular case of derivation that aims to give credit to the source that originated some information. It is recognized that it may be hard to determine which entity constitutes an original source. This definition is inspired by original-source as defined in http://googlenewsblog.blogspot.com/2010/11/credit-where-credit-is-due.html.

An original source relation, written hadOriginalSource(id,e2,e1,attrs)hadOriginalSource(id, e2, e1, a, g2, u1, attrs), has:

  • id: an optional identifier for the relation;
  • derived: an identifier (e2) for the derived entity;
  • source: an identifier (e1) for the original source entity;
  • activity: an optional identifier (a) for the activity using and generating the above entities;
  • generation: an optional identifier (g2) for the generation involving the generated entity (e2) and activity;
  • usage: an optional identifier (u1) for the usage involving the used entity (e1) and activity;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this relation.

Let us consider the concept introduced in the current section, identified as dm:concept-original-source, and the Google page go:credit-where-credit-is-due.html, where the notion original-source was originally described (to the knowledge of the authors).

entity(dm:concept-original-source)
entity(go:credit-where-credit-is-due.html)
hadOriginalSource(dm:concept-original-source,go:credit-where-credit-is-due.html)

4.3.5 Trace

Trace is the ability to link back an entity to another by means of derivation or responsibility relations, possibly repeatedly traversed.

A trace relation between two entities e2 and e1 is a generic dependency of e2 on e1 that indicates either that e1 may have been necessary for e2 to be created, or that e1 bears some responsibility for e2's existence.

A Trace relation , written tracedTo(id,e2,e1,attrs) in PROV-N, has:

  • id: an optional identifier identifying the relation;
  • entity: an identifier (e2) for an entity;
  • ancestor: an identifier (e1) for an ancestor entity that the former depends on;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this relation.

We note that the ancestor is allowed to be an agent since agents are entities.

Derivation and attribution are particular cases of trace.

We refer to the example of Section 3.1, and specifically to Figure 3. We can see that there is a path from tr:WD-prov-dm-20111215 to w3:Consortium and to process:rec-advance. This is expressed as follows.

 tracedTo(tr:WD-prov-dm-20111215,w3:Consortium)
 tracedTo(tr:WD-prov-dm-20111215,process:rec-advance)

4.4 Component 4: Alternate Entities

The fourth component of PROV-DM is concerned with relations specialization and alternate between entities. Figure figure-component4 depicts the fourth component with a single class and two associations.

alternates
Figure 8: Alternates Component Overview

Wherever two people describe the provenance of a same thing, one cannot expect them to coordinate and agree on the identifiers to use to denote that thing.

User Alice writes an article. In its provenance, she wishes to refer to the precise version of the article with a date-specific URI, as she might edit the article later. Alternatively, user Bob refers to the article in general, independently of its variants over time.

To allow for identifiers to be chosen freely and independently by each user, the PROV data model introduces relations that allow entities to be linked together. The following two relations are introduced for expressing specialized or alternate entities.

4.4.1 Specialization

An entity is a specialization of another if they refer to some common thing but the former is a more constrained entity than the latter. The common thing does not need to be identified.

Examples of constraints include a time period, an abstraction, and a context associated with the entity.

A specialization relation, written specializationOf(sub, super) in PROV-N, has:
  • specializedEntity: an identifier (sub) of the specialized entity;
  • generalEntity: an identifier (super) of the entity that is being specialized.

The BBC news home page on 2012-03-23 ex:bbcNews2012-03-23 is a specialization of the BBC news page in general bbc:news/. This can be expressed as follows.

specializationOf(ex:bbcNews2012-03-23, bbc:news/)
We have created a new qualified name, ex:bbcNews2012-03-23, in the namespace ex, to identify the specific page carrying this day's news, which would otherwise be the generic bbc:news/ page.

4.4.2 Alternate

An entity is alternate of another if they are both a specialization of some common entity. The common entity does not need to be identified.

An alternate relation, written alternateOf(e1, e2) in PROV-N, has:
  • alternate1: an identifier (e1) of the first of the two entities;
  • alternate2: an identifier (e2) of the second of the two entities.

A given news item on the BBC News site bbc:news/science-environment-17526723 for desktop is an alternate of a bbc:news/mobile/science-environment-17526723 for mobile devices.

entity(bbc:news/science-environment-17526723, [ prov:type="a news item for desktop"])
entity(bbc:news/mobile/science-environment-17526723, [ prov:type="a news item for mobile devices"])
alternateOf(bbc:news/science-environment-17526723, bbc:news/mobile/science-environment-17526723)

They are both specialization of an (unspecified) entity.

Considering again the two versions of the technical report tr:WD-prov-dm-20111215 (second working draft) and tr:WD-prov-dm-20111018 (first working draft). They are alternate of each other.

entity(tr:WD-prov-dm-20111018)
entity(tr:WD-prov-dm-20111215)
alternateOf(tr:WD-prov-dm-20111018,tr:WD-prov-dm-20111215)

They are both specialization of the page http://www.w3.org/TR/prov-dm/.

4.5 Component 5: Collections

The fifth component of PROV-DM is concerned with the notion of collections. A collection is an entity that has some members. The members are themselves entities, and therefore their provenance can be expressed. Some applications need to be able to express the provenance of the collection itself: e.g. who maintains the collection, which members it contains as it evolves, and how it was assembled. The purpose of Component 5 is to define the types and relations that are useful to express the provenance of collections. In PROV, the concept of Collection is implemented by means of dictionaries, which we introduce in this section.

Figure figure-component5 depicts the fifth component with four new classes and three associations.

dictionaries
Figure 9: Collections Component Overview

The intent of these relations and types is to express the history of changes that occurred to a collection. Changes to collections are about the insertion of entities in collections and the removal of members from collections. Indirectly, such history provides a way to reconstruct the contents of a collection.

4.5.1 Collection

A collection is an entity that provides a structure to some constituents, which are themselves entities. These constituents are said to be member of the collections.

In PROV, the concept of Collection is provided as an extensibility point for other kinds of collections. Collections are implemented by means of dictionaries, which are introduced next.

4.5.2 Dictionary

PROV-DM defines a specific type of collection: a dictionary, specified as follows.

A dictionary is a collection whose members are indexed by keys.

Conceptually, a dictionary has a logical structure consisting of key-entity pairs. This structure is often referred to as a map, and is a generic indexing mechanism that can abstract commonly used data structures, including associative lists (also known as "dictionaries" in some programming languages), relational tables, ordered lists, and more. The specification of such specialized structures in terms of key-value pairs is out of the scope of this document.

A given dictionary forms a given structure for its members. A different structure (obtained either by insertion or removal of members) constitutes a different dictionary. Hence, for the purpose of provenance, a dictionary entity is viewed as a snapshot of a structure. Insertion and removal operations result in new snapshots, each snapshot forming an identifiable dictionary entity.

PROV-DM defines the following types related to dictionaries:

  • prov:Dictionary denotes an entity of type dictionary, i.e. an entity that can participate in relations amongst dictionaries;
  • prov:EmptyDictionary denotes an empty dictionary.
entity(d0, [prov:type="prov:EmptyDictionary" %% xsd:QName])  // d0 is an empty dictionary
entity(d1, [prov:type="prov:Dictionary"  %% xsd:QName])      // d1 is a dictionary, with unknown content

4.5.3 Insertion

Insertion is a derivation that transforms a dictionary into another, by insertion of one or more key-entity pairs.

An Insertion relation, written derivedByInsertionFrom(id, d2, d1, {(key_1, e_1), ..., (key_n, e_n)}, attrs), has:

  • id: an optional identifier identifying the relation;
  • after: an identifier (d2) for the dictionary after insertion;
  • before: an identifier (d1) for the dictionary before insertion;
  • key-entity-set: the inserted key-entity pairs (key_1, e_1), ..., (key_n, e_n) in which each key_i is a value, and e_i is an identifier for the entity that has been inserted with the key; each key_i is expected to be unique for the key-entity-set;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this relation.

An Insertion relation derivedByInsertionFrom(id, d2, d1, {(key_1, e_1), ..., (key_n, e_n)}) states that d2 is the state of the dictionary following the insertion of pairs (key_1, e_1), ..., (key_n, e_n) into dictionary d1.

entity(d0, [prov:type="prov:EmptyDictionary" %% xsd:QName])    // d0 is an empty dictionary
entity(e1)
entity(e2)
entity(e3)
entity(d1, [prov:type="prov:Dictionary" %% xsd:QName])
entity(d2, [prov:type="prov:Dictionary" %% xsd:QName])

derivedByInsertionFrom(d1, d0, {("k1", e1), ("k2", e2)})       
derivedByInsertionFrom(d2, d1, {("k3", e3)})    
From this set of descriptions, we conclude:
  • d0 is the set { }
  • d1 is the set { ("k1", e1), ("k2", e2) }
  • d2 is the set { ("k1", e1), ("k2", e2), ("k3", e3) }

Insertion provides an "update semantics" for the keys that are already present in a dictionary, since a new pair replaces an existing pair with the same key in the new dictionary. This is illustrated by the following example.

entity(d0, [prov:type="prov:EmptyDictionary" %% xsd:QName])    // d0 is an empty dictionary
entity(e1)
entity(e2)
entity(e3)
entity(d1, [prov:type="prov:Dictionary" %% xsd:QName])
entity(d2, [prov:type="prov:Dictionary" %% xsd:QName])

derivedByInsertionFrom(d1, d0, {("k1", e1), ("k2", e2)})       
derivedByInsertionFrom(d2, d1, {("k1", e3)})    
This is a case of update of e1 to e3 for the same key, "k1".
From this set of descriptions, we conclude:
  • d0 is the set { }
  • d1 is the set { ("k1", e1), ("k2", e2) }
  • d2 is the set { ("k1", e3), ("k2", e2) }

4.5.4 Removal

Removal is a derivation that transforms a dictionary into another, by removing one or more key-entity pairs.

A Removal relation, written derivedByRemovalFrom(id, d2, d1, {key_1, ... key_n}, attrs), has:

  • id: an optional identifier identifying the relation;
  • after: an identifier (d2) for the dictionary after the deletion;
  • before: an identifier (d1) for the dictionary before the deletion;
  • key-set: a set of deleted keys key_1, ..., key_n, for which each key_i is a value;
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this relation.

A Removal relation derivedByRemovalFrom(id, d2,d1, {key_1, ..., key_n}) states that d2 is the state of the dictionary following the removal of the set of pairs corresponding to keys key_1...key_n from d1.

entity(d0, [prov:type="prov:EmptyDictionary"])    // d0 is an empty dictionary
entity(e1)
entity(e2)
entity(e3)
entity(d1, [prov:type="prov:Dictionary"])
entity(d2, [prov:type="prov:Dictionary"])

derivedByInsertionFrom(d1, d0, {("k1", e1), ("k2",e2)})       
derivedByInsertionFrom(d2, d1, {("k3", e3)})
derivedByRemovalFrom(d3, d2, {"k1", "k3"})   
From this set of descriptions, we conclude:
  • d0 is the set { }
  • d1 is the set { ("k1", e1), ("k2", e2) }
  • d2 is the set { ("k1", e1), ("k2", e2), ("k3", e3) }
  • d3 is the set { ("k2", e2) }

4.5.5 Membership

Membership is the belonging of a key-entity pair to dictionary.

The insertion and removal relations make insertions and removals explicit as part of the history of a dictionary. This, however, requires explicit mention of the state of the dictionary prior to each operation. The membership relation removes this needs, allowing the state of a dictionary c to be expressed without having to introduce a prior state.

A membership relation, written memberOf(id, c, {(key_1, e_1), ..., (key_n, e_n)}, cplt, attrs), has:
  • id: an optional identifier identifying the relation;
  • after: an identifier (c) for the dictionary whose members are asserted;
  • key-entity-set: a set of key-entity pairs (key_1, e_1), ..., (key_n, e_n) that are members of the dictionary;
  • complete: an optional boolean Value (cplt); if true, it indicates that no other member belongs to the dictionary; if false, it indicates that other members belong to the dictionary; if unspecified, other members may belong to the dictionary.
  • attributes: an optional set (attrs) of attribute-value pairs representing additional information about this relation.

The description memberOf(c, {(key_1, e_1), ..., (key_n, e_n)}) states that c is known to include (key_1, e_1), ..., (key_n, e_n)}, without having to introduce a previous state.

entity(d1, [prov:type="prov:Dictionary"  %% xsd:QName])    // d1 is a dictionary, with unknown content
entity(d2, [prov:type="prov:Dictionary"  %% xsd:QName])    // d2 is a dictionary, with unknown content

entity(e1)
entity(e2)

memberOf(d1, {("k1", e1), ("k2", e2)} )  
memberOf(d2, {("k1", e1), ("k2", e2)}, true)  

entity(e3)
entity(d3, [prov:type="prov:Dictionary"  %% xsd:QName])

derivedByInsertionFrom(d3, d1, {("k3", e3)})     
From these descriptions, we conclude:
  • d1 has the following pairs as members: ("k1", e1), ("k2", e2), and may contain others.
  • d2 exactly has the following pairs as members: ("k1", e1), ("k2", e2), and does not contain any other.
  • d3 has the following pairs as members: ("k1", e1), ("k2", e2), ("k3", v3), and may contain others.

Thus, the states of d1 and d3 are only partially known.

Further considerations:

4.6 Component 6: Annotations

The sixth component of PROV-DM is concerned with notes and annotations.

As provenance descriptions are exchanged between systems, it may be useful for a third party to add extra information to what they are describing. For instance, a "trust service" may add value-judgements about the trustworthiness of some of the entities or agents occurring in provenance records it is given access to. Likewise, an interactive visualization component may want to enrich an existing set of provenance descriptions with information helping reproduce their visual representation. To help with interoperability, PROV-DM introduces a simple annotation mechanism allowing anything that is identifiable to be associated with notes. For this, a type and and a relation are introduced.

The annotation mechanism (with note and annotation) forms a key aspect of the extensibility mechanism of PROV-DM (see extensibility section).

4.6.1 Note

A note is an identified set of application-specific attribute-value pairs.

A note, written note(id, [attr1=val1, ...]) in PROV-N, has:
  • id: an identifier for a note;
  • attributes: a set of attribute-value pairs ((attr1, val1), ...) representing application-specific information.

The following note consists of a set of application-specific attribute-value pairs, intended to help the rendering of the pre-existing entity it is associated with, by specifying its color and its position on the screen.

note(ex:n1,[draw:color="blue", draw:screenX=20, draw:screenY=30])
hasAnnotation(tr:WD-prov-dm-20111215,ex:n1)

The note is linked to the entity tr:WD-prov-dm-20111215, with relation hasAnnotation discussed in Section 4.6.2. The note's identifier is declared in the namespace denoted by prefix ex to illustrate that the rendering application may differ from the application involving entity tr:WD-prov-dm-20111215. The prefix draw also denotes an application-specificapplication specific namespace.

In contrast, a reputation service may enrich an existing provenance record with notes providing reputation ratings about agents. In the following fragment, both agents ex2:Simon and ex2:Paolo are rated "excellent".

note(ex3:n2,[trust:reputation="excellent"])
hasAnnotation(ex2:Simon,ex3:n2)
hasAnnotation(ex2:Paolo,ex3:n2)

The note's identifier is declared in a separate namespace denoted by prefix ex3. The prefix trust also denotes an application specific namespace.

4.6.2 Annotation

An annotation is a link between something that is identifiable and a note referred to by its identifier.

Multiple notes can be associated with a given identified object; symmetrically, multiple objects can be associated with a given note. Since notes have identifiers, they can also be annotated.

An annotation relation, written hasAnnotation(r,n) in PROV-N, has:
  • something: the identifier (r) of something being annotated;
  • note: an identifier (n) of a note.

The following expressions

entity(e1,[prov:type="document"])
entity(e2,[prov:type="document"])
activity(a,t1,t2)
used(u1,a,e1,[ex:file="stdin"])
wasGeneratedBy(e2, a, [ex:file="stdout"])

note(n1,[ex:icon="doc.png"])
hasAnnotation(e1,n1)
hasAnnotation(e2,n1)

note(n2,[ex:style="dotted"])
hasAnnotation(u1,n2)

describe two documents (attribute-value pair: prov:type="document") identified by e1 and e2, and their annotation with a note indicating that the icon (an application specific way of rendering provenance) is doc.png. The example also includes an activity, its usage of the first entity, and its generation of the second entity. The usage is annotated with a style (an application specific way of rendering this edge graphically). To be able to express this annotation, the usage was provided with an identifier u1, which was then referred to in hasAnnotation(u1,n2).

4.7 Further Elements of PROV-DM

This section introduces further elements of PROV-DM.

4.7.1 Namespace Declaration

A PROV-DM namespace is identified by an IRI [IRI]. In PROV-DM, attributes, identifiers, and values with qualified names as data type can be placed in a namespace using the mechanisms described in this specification.

A namespace declaration consists of a binding between a prefix and a namespace. Every qualified name with this prefix in the scope of this declaration refers to this namespace. A default namespace declaration consists of a namespace. Every un-prefixed qualified name in the scope of this default namespace declaration refers to this namespace.

The PROV namespace is identified by the URI http://www.w3.org/ns/prov#.

4.7.2 Qualified Name

A qualified name is a name subject to namespace interpretation. It consists of a namespace, denoted by an optional prefix, and a local name.

PROV-DM stipulates that a qualified name can be mapped into an IRI by concatenating the IRI associated with the prefix and the local part.

A qualified name's prefix is optional. If a prefix occurs in a qualified name, it refers to a namespace declared in a namespace declaration. In the absence of prefix, the qualified name refers to the default namespace.

4.7.3 Identifier

An identifier is a qualified name.

4.7.4 Attribute

An attribute is a qualified name.

The PROV data model introduces a pre-defined set of attributes in the PROV namespace, which we define below. This specification does not provide any interpretation for any attribute declared in any other namespace.

Table 5: PROV-DM Attributes At a Glance
AttributevalueSection
prov:labelxsd:stringSection 4.7.4.1
prov:locationValueSection 4.7.4.2
prov:roleValueSection 4.7.4.3
prov:typeValueSection 4.7.4.4
prov:valueValueSection 4.7.4.5
4.7.4.1 prov:label

The attribute prov:label provides a human-readable representation of a PROV-DM element or relation. The value associated with the attribute prov:label must be a string.

The following entity is provided with a label attribute.

 entity(ex:e1, [prov:label="This is a label"])
4.7.4.2 prov:location

A location can be an identifiable geographic place (ISO 19112), but it can also be a non-geographic place such as a directory, row, or column. As such, there are numerous ways in which location can be expressed, such as by a coordinate, address, landmark, and so forth. This document does not specify how to concretely express locations, but instead provide a mechanism to introduce locations, by means of a reserved attribute.

The attribute prov:location is an optional attribute of entity, activity, usage, and generation. The value associated with the attribute prov:location must be a PROV-DM Value, expected to denote a location.

The following expression describes entity Mona Lisa, a painting, with a location attribute.

 entity(ex:MonaLisa, [prov:location="Le Louvres, Paris", prov:type="StillImage"])
4.7.4.3 prov:role

The attribute prov:role denotes the function of an entity with respect to an activity, in the context of a usage, generation,usage, generation, association,association, start,start, and end.end. The attribute prov:role is allowed to occur multiple times in a list of attribute-value pairs. The value associated with a prov:role attribute must be a PROV-DM Value.

The following activity is associated with an agent acting as the operator.

 wasAssociatedWith(a, ag, [prov:role="operator"])
4.7.4.4 prov:type

The attribute prov:type provides further typing information for an element or relation. PROV-DM liberally defines a type as a category of things having common characteristics. PROV-DM is agnostic about the representation of types, and only states that the value associated with a prov:type attribute must be a PROV-DM Value. The attribute prov:type is allowed to occur multiple times.

The following describes an agent of type software agent.

   agent(ag, [prov:type="prov:SoftwareAgent" %% xsd:QName])

The following types are pre-defined in PROV, and are valid values for the prov:type attribute.

  • prov:Plan
  • prov:Account
  • prov:SoftwareAgent
  • prov:Organization
  • prov:Person
  • prov:Collection
  • prov:Dictionary
  • prov:EmptyDictionary
4.7.4.5 prov:value

The attribute prov:value provides a Value associated with an entity.

The attribute prov:value is an optional attribute of entity. The value associated with the attribute prov:value must be a PROV-DM Value. The attribute prov:value may occur at most once in a set of attribute-value pairs.

The following example illustrates the provenance of the number 4 obtained by an activity that computed the length of an input string "abcd". The input and the output are expressed as entities ex:in and ex:out, respectively. They each have a prov:value attribute associated with the corresponding value.

entity(ex:in, [prov:value="abcd"]) 
entity(ex:out, [prov:value=4]) 
activity(ex:len, [prov:type="string-length"])
used(ex:len,ex:in)
wasGeneratedBy(ex:out,ex:len)
wasDerivedFrom(ex:out,ex:in)
Should we also have prov:encoding?

4.7.5 Value

By means of attribute-value pairs, the PROV data model can refer to values such as strings, numbers, time, qualified names, and IRIs. The interpretation of such values is outside the scope of PROV-DM.

Each kind of such values is called a datatype. The datatypes are taken from the set of XML Schema Datatypes, version 1.1 [XMLSCHEMA-2] and the RDF specification [RDF-CONCEPTS]. The normative definitions of these datatypes are provided by the respective specifications. Each datatype is identified by its XML xsd:QName.

We note that PROV-DM time instants are defined according to xsd:dateTime [XMLSCHEMA-2].

Table 6: PROV-DM Data Types
xsd:decimal xsd:double xsd:dateTime
xsd:integer xsd:float
xsd:nonNegativeInteger xsd:string rdf:XMLLiteral
xsd:nonPositiveIntegerxsd:normalizedString
xsd:positiveInteger xsd:token
xsd:negativeInteger xsd:language
xsd:long xsd:Name
xsd:int xsd:NCName
xsd:short xsd:NMTOKEN
xsd:byte xsd:boolean
xsd:unsignedLong xsd:hexBinary
xsd:unsignedInt xsd:base64Binary
xsd:unsignedShortxsd:anyURI
xsd:unsignedByte xsd:QName

The following examples respectively are the string "abc", the integer number 1, and the IRI "http://example.org/foo".

  "abc"
  1
  "http://example.org/foo" %% xsd:anyURI

The following example shows a value of type xsd:QName (see QName [XMLSCHEMA-2]). The prefix ex must be bound to a namespace declared in a namespace declaration.

 
  "ex:value" %% xsd:QName

In the following example, the generation time of entity e1 is expressed according to xsd:dateTime [XMLSCHEMA-2].

 
  wasGeneratedBy(e1,a1, 2001-10-26T21:32:52)
We need to check that we are including all xsd types that are the latest versions of XML Schema/RDF.

5. PROV-DM Extensibility Points

The PROV data model provides extensibility points that allow designers to specialize it to specific applications or domains. We summarize these extensibility points here:

The PROV data model is designed to be application and technology independent, but specializations of PROV-DM are welcome and encouraged. To ensure interoperability, specializations of the PROV data model that exploit the extensibility points summarized in this section must preserve the semantics specified in this document and in [PROV-CONSTRAINTS].

6. Creating Valid Provenance

A. Acknowledgements

WG membership to be listed here.

B. References

B.1 Normative references

[IRI]
M. Duerst, M. Suignard. Internationalized Resource Identifiers (IRI). January 2005. Internet RFC 3987. URL: http://www.ietf.org/rfc/rfc3987.txt
[RDF-CONCEPTS]
Graham Klyne; Jeremy J. Carroll. Resource Description Framework (RDF): Concepts and Abstract Syntax. 10 February 2004. W3C Recommendation. URL: http://www.w3.org/TR/2004/REC-rdf-concepts-20040210
[RFC2119]
S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. March 1997. Internet RFC 2119. URL: http://www.ietf.org/rfc/rfc2119.txt
[URI]
T. Berners-Lee; R. Fielding; L. Masinter. Uniform Resource Identifiers (URI): generic syntax. January 2005. Internet RFC 3986. URL: http://www.ietf.org/rfc/rfc3986.txt
[XMLSCHEMA-2]
Paul V. Biron; Ashok Malhotra. XML Schema Part 2: Datatypes Second Edition. 28 October 2004. W3C Recommendation. URL: http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/

B.2 Informative references

[Logic]
W. E. JohnsonLogic: Part III.1924. URL: http://www.ditext.com/johnson/intro-3.html
[PROV-AQ]
Graham Klyne and Paul Groth (eds.) Luc Moreau, Olaf Hartig, Yogesh Simmhan, James Meyers, Timothy Lebo, Khalid Belhajjame, and Simon Miles Provenance Access and Query. 2011, Working Draft. URL: http://www.w3.org/TR/prov-aq/
[PROV-CONSTRAINTS]
James Cheney, Paolo Missier, and Luc Moreau (eds.) Constraints of the PROV Data Model. 2011, Working Draft. URL: http://www.w3.org/TR/prov-constraints/
[PROV-N]
Luc Moreau and Paolo Missier (eds.)PROV-N: The Provenance Notation. 2011, Working Draft. URL: http://www.w3.org/TR/prov-n/
[PROV-O]
Satya Sahoo and Deborah McGuinness (eds.) Khalid Belhajjame, James Cheney, Daniel Garijo, Timothy Lebo, Stian Soiland-Reyes, and Stephan Zednik Provenance Formal Model. 2011, Working Draft. URL: http://www.w3.org/TR/prov-o/
[PROV-PRIMER]
Yolanda Gil and Simon Miles (eds.) Khalid Belhajjame, Helena Deus, Daniel Garijo, Graham Klyne, Paolo Missier, Stian Soiland-Reyes, and Stephan Zednik Prov Model Primer. 2011, Working Draft. URL: http://www.w3.org/TR/prov-primer/
[PROV-SEM]
James Cheney Formal Semantics Strawman. 2011, Work in progress. URL: http://www.w3.org/2011/prov/wiki/FormalSemanticsStrawman