--- a/model/ProvenanceModel.html Tue Sep 06 21:40:00 2011 +0100
+++ b/model/ProvenanceModel.html Tue Sep 06 22:11:32 2011 +0100
@@ -583,6 +583,8 @@
its attributes are assigned a value as part of that assertion.
</li>
+<li>Activities are not represented by entities, but instead by process
+executions, as explained below.</li>
</ul>
@@ -606,9 +608,26 @@
<section id="expression-ProcessExecution">
<h3>Process Execution</h3>
-<p>A <dfn id="dfn-ProcessExecution">process execution</dfn> represents an identifiable activity, which performs a piece of work.</p>
+<p>In PIDM, a <dfn id="dfn-ProcessExecution">process execution expression</dfn> is a representation an identifiable activity, which performs a piece of work.</p>
-<p>The activity that a process execution represents has a duration, delimited by its start and its end; hence, it occurs over a continuous time interval. However, the process execution representing the activity need not mention time information, nor duration, because they may not be known.</p>
+<p>In the Provenance Abstract Syntax Notation, a process execution expression's text matches the <span class='nonterminal'>process execution</span> production of the grammar defined in this specification document.</p>
+
+<div class='grammar'>
+<span class="nonterminal">processExecution</span> :=
+<span class="name">processExecution</span>
+<span class="name">(</span>
+<span class="nonterminal">identifier</span>
+[<span class="name">,</span>
+<span class="nonterminal">recipe</span>]
+[<span class="name">,</span>
+<span class="nonterminal">time</span>]
+[<span class="name">,</span>
+<span class="nonterminal">time</span>]
+<span class="name">)</span><br/>
+</div>
+
+
+<p>The activity that a process execution is a representation of has a duration, delimited by its start and its end events; hence, it occurs over an interval delimited by two events. However, a process execution need not mention time information, nor duration, because they may not be known.</p>
<p> A process execution assertion, noted <span class="name">processExecution(id,rl,st,et)</span>:
<ul>
@@ -620,11 +639,19 @@
</p>
<p>
+The following process execution assertion
<pre class="example">
processExecution(pe1,add-crime-in-london,t+1,t+1+epsilon)
</pre>
+states the existence of an activity, denoted by identifier <span class="name">id</span>, with recipe link <span class="name">add-crime-in-london</span>, start time <span class="name">t+1</span>, and end time <span class="name">t+1+epsilon</span>.
</p>
+<p>The mere existence of a process execution assertion entails some event ordering in the world, since the start event preceds the end event. This expressed by constraint <a href='#start-precedes-end'>start-precedes-end</a>.</p>
+
+<div class='constraint' id='start-precedes-end'><a name="PIL:0001"> From the assertion of a process execution, one can infer that the
+start precedes the end of the represented activity.</a> [<a
+href="../ontology/ProvenanceFormalModel.html#PIL:0001">PIL:0001</a>] </div>
+
<p>A process execution is not an entity. Indeed, an entity represents
a thing that exists in full at any point in its characterization
interval, persists during this interval, and preserves the
@@ -633,17 +660,7 @@
but is typically not identifiable by the characteristics it exhibits at
any point during its duration.</p>
-
-<div class='note'>Elaborate justification. </div>
-
-
-
-<div class='constraint' id='start-precedes-end'><a name="PIL:0001"> From the assertion of a process execution, one can infer that the
-start precedes the end of the represented activity.</a> [<a
-href="../ontology/ProvenanceFormalModel.html#PIL:0001">PIL:0001</a>] </div>
-
-
-<div class='pending'>Should process execution be defined as a subclass of BOB. This is <a href="http://www.w3.org/2011/prov/track/issues/66">ISSUE-66</a>.</div>
+<div class='resolved'>Should process execution be defined as a subclass of BOB. This is <a href="http://www.w3.org/2011/prov/track/issues/66">ISSUE-66</a>.</div>
</section>
<section id="expression-Generation">