PROV-DM Misc PROPOSALS to Vote On

Proposal 1: On Entity Invalidation

Context: Activities have a start and an end (corresponding to event defined in part II). Entities have a characterization interval, with a generation event marking the interval beginning, but no event marking the interval end.

It is proposed to introduce an explicit event that marks the end of an entity characterization interval. Some suggested that it could be a "invalidation" event, others felt the term invalidation is too strong, but no alternate term has been proposed so far.

PROPOSED: to introduce a prov-dm concept that marks the end of an entity lifetime. Its name remains to be determined.

Suggested names:

invalidation,
expiration,
final usage,
destruction
lostFormBy

For now, INVALIDATION is used as placeholder name

The text would include the following.

Tentative definition: Invalidation is the end of an entity's lifetime. This entity becomes unavailable for usage after invalidation. This entity no longer exists after invalidation. Any generation or usage of an entity precedes its invalidation.

Invalidation, written wasInvalidatedBy(id,e,a,t,attrs) in PROV-ASN, has the following components:

id: an OPTIONAL identifier for a invalidation;
entity: an identifier for the destroyed entity;
activity: an OPTIONAL identifier for the activity that destroys the entity;
time: an OPTIONAL "invalidation time", the time at which the entity began to be destroyed;
attributes: an OPTIONAL set of attribute-value pairs that describes the modalities of invalidation of this entity by this activity.

While each of the components activity, time, and attributes is OPTIONAL, at least one of them MUST be present.

In the following example, invalidation is caused by a new version of an entity being made available. Let us consider the resource tr:prov-dm when it was the first working draft (attribute ex:version=1). This resource was no longer the first working draft, as soon as the second working draft was published. Hence, tr:prov-dm was invalidated by ex:act2, when it published tr:WD-prov-dm-20111215.

entity(tr:prov-dm,[prov:type="working draft", ex:version="1"])
wasInvalidatedBy(tr:prov-dm,ex:act2,2011-12-15T16:00:00)
activity(ex:act2,,,[prov:type="publish"])
wasGeneratedBy(tr:WD-prov-dm-20111215, ex:act2,2011-12-15T16:00:00)

In the following example, invalidation is caused by the disappearance of an entity. Let us consider the proceedings of the 2002 Chicago provenance workshop. They used to be hosted at http://people.cs.uchicago.edu/~yongzh/position_papers.html, and were lost as a researcher left the hosting institution. The proceedings were restored at ipaw:2002.

entity(chicago:wkshp2002,[prov:type="workshop talks"])
wasInvalidatedBy(chicago:wkshp2002,2010-08-21T00:00:00)

entity(ipaw:wkshp2002,[prov:type="workshop talks"])
activity(ex:restore,[prov:type="Restore"])
wasGeneratedBy(ipaw:wkshp2002,ex:restore,2012-03-09T0:00:00)
wasDerivedFrom(ipaw:wkshp2002,chicago:wkshp2002)

Proposal 2: Activity Start and End without Responsibility

Context: The motivation for introducing agents in prov-dm is to denote the agent's responsibility for activities. It is however impossible to describe the start/end of an activity without introducing agents, and therefore assigning responsibility.

PROPOSED: to formulate start and end of activities independently of responsibility and agents. Hence, start and end of activity would no longer be a form of activity association. Instead of an agent, an optional entity trigger would be allowed.

The text would include the following.

Start is when an activity is deemed to have started. The activity did not exist before its start. Any usage, generation, or invalidation involving an activity follows its start. 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 its end.

An activity start, written wasStartedBy(id,a,e,t,attrs) in PROV-ASN, contains:

id: an OPTIONAL identifier for the activity start;
activity: an identifier for the started activity;
trigger: an identifier for the entity triggering the activity;
time: the time at which the activity was started;
attributes: an OPTIONAL set of attribute-value pairs describing modalities according to which the activity was started.

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 activity happens to consume the message content, then the message would also be regarded as an input to the activity, which we describe as follows:

used(a1,e1)

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

An activity end, written wasEndedBy(id,a,e,t,attrs) in PROV-ASN, contains:

id: an OPTIONAL identifier for the activity end;
activity: an identifier for the ended activity;
trigger: an identifier for the entity triggering the activity ending;
time: the time at which the activity was ended;
attributes: an OPTIONAL set of attribute-value pairs describing modalities according to which the activity was ended.

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)

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

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

Constraints need to be added to part II, to ensure that time information on activity matches time information on Start/End.

Proposal 1: On Entity Invalidation

Proposal 2: Activity Start and End without Responsibility

Proposal 3: Activity Started/Ended by Another Activity