--- a/model/working-copy/prov-asn.html	Tue Feb 07 21:19:07 2012 +0000
+++ b/model/working-copy/prov-asn.html	Tue Feb 07 21:48:50 2012 +0000
@@ -177,6 +177,13 @@
 <h2>Preliminaries</h2>
 -->
 
+<p>This specification also introduces
+PROV-ASN, an abstract syntax that is primarily aimed at human consumption. PROV-ASN allows
+serializations of PROV-DM instances to be written in a technology independent manner,
+it facilitates its mapping to concrete syntax, and it is used as the basis for a
+formal semantics. This specification uses instances of provenance written in PROV-ASN 
+to illustrate the data model. 
+</p>
 
 <section id="data-model-concepts"> 
 

--- a/model/working-copy/towards-wd4.html	Tue Feb 07 21:19:07 2012 +0000
+++ b/model/working-copy/towards-wd4.html	Tue Feb 07 21:48:50 2012 +0000
@@ -203,7 +203,14 @@
 that are necessary to achieve this vision in an inter-operable
 way, the first of which is this document:</p>
 <ul>
-<li>PROV-DM: a data model for provenance, accompanied with a notation to express instances of that data model for human consumption (this document); </li>
+<li>A data model for provenance, which is presented in three documents:
+<ul>
+<li> PROV-DM (part I): the provenance data model itself, expressed in natural language (this document);
+<li> PROV-DM-CONSTRAINTS (part II): constraints underpinning the data model (REF TO ADD);
+<li> PROV-ASN (part III): a notation to express instances of that data model for human consumption (REF TO ADD);
+</ul> 
+</li>
+
 <li>PROV-O: a normative serialization of PROV-DM in RDF [[!PROV-O]], specified by means of a mapping to the OWL2 Web Ontology Language [[!OWL2-SYNTAX]];</li>
 <li>PROV-AQ: the mechanisms for accessing and querying provenance [[!PROV-AQ]];</li>
 <li>PROV-PRIMER: a primer for the PROV approach [[!PROV-PRIMER]];</li>
@@ -216,35 +223,28 @@
 concepts, and a few common relations, based on these core concepts.  PROV-DM is a domain-agnotisc model, but with clear extensibility points allowing further domain-specific and
 application-specific extensions to be defined.</p>
 
-<p>This specification also introduces
-PROV-ASN, an abstract syntax that is primarily aimed at human consumption. PROV-ASN allows
-serializations of PROV-DM instances to be written in a technology independent manner,
-it facilitates its mapping to concrete syntax, and it is used as the basis for a
-formal semantics. This specification uses instances of provenance written in PROV-ASN 
-to illustrate the data model. 
+<p>This specification intentionally presents the key concepts of the PROV Data Model, without drilling down into all its subtleties.  Using these key concepts, it becomes possible to write useful provenance assertions very quickly, and publish or embed them along side the data they relate to. </p>
+
+<p>However, it becomes challenging for provenance, like for any other form of metadata, when the data it is about changes. To address this challenge, an <em>upgrade path</em> is proposed to enrich simple provenance assertions, with extra-assertions that  help qualify the subject of provenance and provenance itself, with attributes and interval, intended to satisfy a comprehensive set of constraints.  These aspects are covered in the companion specification (PROV-DM part II, Ref to ADD).
 </p>
 
+
     <section id="structure-of-this-document"> 
 <h3>Structure of this Document</h3>
 
-<p>In <a href="#preliminaries">section 2</a>, a set of preliminaries are introduced, including concepts that underpin PROV-DM and motivations for the PROV-ASN notation.</p>
+<p><a href="#prov-dm-overview">Section 2</a> provides an overview of PROV-DM listing its core types and their relations.</p>
 
-<p><a href="#prov-dm-overview">Section 3</a> provides an overview of PROV-DM listing its core types and their relations.</p>
-
-<p>In <a href="#prov-dm-example">section 4</a>, PROV-DM is
+<p>In <a href="#prov-dm-example">section 3</a>, PROV-DM is
 applied to a short scenario, encoded in PROV-ASN, and illustrated
 graphically.</p>
 
-<p><a href="#data-model-concepts">Section 5</a> provides the normative definition of PROV-DM and the notation PROV-ASN.</p>
-
-<p><a href="#common-relations">Section 6</a> introduces further relations offered by PROV-DM, including relations for data collections and domain-independent common relations.</p>
+<p><a href="#data-model-concepts">Section 4</a> provides the normative definition of PROV-DM.</p>
 
-<p><a href="#interpretation">Section 7</a> provides an interpretation of PROV-DM in terms of ordering constraints between events, and also presents a set of structural constraints to be
-satisfied by PROV-DM.</p>
+<p><a href="#common-relations">Section 5</a> introduces further relations offered by PROV-DM, including relations for data collections and domain-independent common relations.</p>
 
-<p><a href="#extensibility-section">Section 8</a> summarizes PROV-DM extensibility points.</p>
+<p><a href="#extensibility-section">Section 6</a> summarizes PROV-DM extensibility points.</p>
 
-<p><a href="#resource-section">Section 9</a> discusses how PROV-DM can be applied to the notion of resource.</p>
+<p><a href="#FurtherConsiderations">Section 7</a> discusses further considerations of the PROV data model.</p>
 
 
     </section> 
@@ -1627,15 +1627,62 @@
 </section>
 </section>
 
+    <section id="extensibility-section"> 
+<h2>PROV-DM Extensibility Points</h2>
+
+
+<p>The PROV data model provides several extensibility points that allow designers to specialize it to specific applications or domains. We summarize these extensibility points here:
+
+<ul>
+<li> Attributes are constructs of the data model that allow representations of aspects of the world's entities and activities to be expressed.  Applications are free to introduce
+application-specific attributes, according to their perspective on the world.  Attributes for a given application can be distinguished by qualifying them with a prefix denoting a namespace
+declared in a namespace declaration.
+
+<p>The <a href="#prov-dm-namespace">PROV-DM namespace</a> declares a set of reserved attributes catering for extensibility: <span class="name">type</span>, <span
+class="name">location</span>.</li>
+
+
+<li> Sets of Attribute-value pairs offer a mechanism to
+describe modalities of use, generation, and control  
+Such attributes are also qualified by namespaces.
+
+<p>To this end, the <a href="#prov-dm-namespace">PROV-DM namespace</a> declares a reserved attribute: <span class="name">role</span>.</p></li>
+
+
+<li>Notes allow arbitrary metadata to be associated with anything identifiable in PROV-DM. Notes consist of name-value pairs. Like attributes, names are qualified by a
+namespace.</li>
+
+
+<li>Namespaces allow attributes and names to be qualified. </li>
+
+<li>Subtyping of elements and relations is allowed by means of the reserved attribute <span class="name">type</span>.</li>
+
+<li>Domain specific values can be expressed by means of typed literals. </li>
+</ul>
+
+<p>The PROV data model is designed to be application and technology independent, but specializations of PROV-DM are welcome and encouraged.  To ensure inter-operability, specializations of
+the PROV data model that exploit the extensibility points summarized in this section MUST preserve the semantics specified in this document. For instance, a qualified attribute on a domain
+specific entity MUST represent an aspect of an entity and this aspect MUST remain unchanged during the characterization's interval of this entity record.</p>
+
+
+
+    </section> 
+
+
+
 <section id="FurtherConsiderations">
 <h4>Further Considerations</h4>
 
+<div class='note'>
+TODO: gives a high level taster for part II
+</div>
+
 <ul>
 <li> Provenance of Provenance and Provenance from Multiple Perspectives/Providers 
 
 <li> Ordering Constraints 
 
-<li>
+<li> Attributes, fixed values over some intervals.
 </ul>