--- a/model/satya-comments-issue-100.txt	Mon Nov 07 12:06:35 2011 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,121 +0,0 @@
-
-  > My review comments for Section 5.2.1 Entity in the current version of the conceptual model document:
-  > 
-  > 1. In PROV-DM, an entity expression is a representation of an
-  > identifiable characterized thing.
-  > 
-  > Issue: Since the section heading is for Entity and the PROV DM
-  > component is Entity, I am confused why we are defining "Entity
-  > Expression" and not "Entity"?
-
-An instance of an entity expression is syntactally written as
-'entity', but we use the term 'entity record' (was 'entity
-expression') to make it clear that we refer to a PROV-DM construct and
-not a thing in the world (see intro of section 5.1)
-
-We also tried to make the distinction between the model and language clearer.
-So, we use 'records' to talk about prov-dm. 
-
-In section 2.2, we now write:
-
-  This specification also relies on a language, PROV-ASN, the
-  Provenance Abstract Syntax Notation, to express instances of that
-  data model. For each construct of PROV-DM, a corresponding ASN
-  expression is introduced, by way of a production in the ASN grammar.
-
-
-  > 
-  > 2. An instance of an entity expression, noted entity(id, [ attr1=val1,
-  > ...]) in PROV-ASN contains an identifier id identifying a
-  > characterized thing; contains a set of attribute-value pairs [
-  > attr1=val1, ...], representing this characterized thing's situation in
-  > the world.
-  > 
-  > Issue: When we refer to an entity in provenance assertions (in
-  > different applications), do we use the identifier to refer to it or
-  > both identifier + attribute-value pairs?
-
-Not sure I understand (in different applications).
-
-We refer to it with its identifier.
-
-
-  > 
-  > 3. The assertion of an instance of an entity expression, entity(id, [
-  > attr1=val1, ...]), states, from a given asserter's viewpoint, the
-  > existence of an identifiable characterized thing, whose situation in
-  > the world is represented by the attribute-value pairs, which remain
-  > unchanged during a characterization interval, i.e. a continuous
-  > interval between two events in the world.
-  > 
-  > Issue: Are the terms "characterization interval" and "continuous
-  > interval" defined by time values? What do we mean by "continuous
-  > interval" between two events?
-
-We assumed a partial order between events.
-An interval between events a and b [a,b] is the set of events x  such that a<= x and x<=b.
-
-Does it really need to be defined explicitly?
-
-PM there is a hidden issue here though: how do we get agreement on event ordering? isn't this a way to sweep agreement on time under the rug?
-I am not competent enough to see this through I'm afraid but I see this will creep back up on us
-
-Luc: The reference to Lamport is crucial here.  There is ordering in
-distributed systems because the receipt of a message always follows
-its sending.
-
-  We have extended that to: the use of an entity, follows its
-  generation.  And, the end of a PE follows its start.  All event
-  ordering constraints build on those two.
-
-Luc: it would be good to identify the events that delimit a characterization interval.
-  I don't think we have a precise answer for that.
-  Start would be a generation event.
-  End could be the generation of a new entity  luc, age=10  terminates luc, age=9
-  End could be the destructive consumption of an entity: egg broken to make a cake
-
-Luc: events are not observable, but time is. Not global time, but local time, found
-on local clocks, more or less synchronized.
-
-
-
-  > 4. If an asserter wishes to characterize a thing with the same
-  > attribute-value pairs over several intervals, then they are required
-  > to assert multiple entity expressions, each with its own identifier
-  > (so as to allow potential dependencies between the various entity
-  > expressions to be expressed).
-  > 
-  > Issue: If a thing with same attribute-value pairs exists over several
-  > time? intervals - what will be the dependencies between the various
-  > entity expressions (since entity expressions = identifier +
-  > attribute-value pairs)? If they are different versions of an entity,
-  > they will have distinguishing attributes other than the simple
-  > occurrence at different points of time. Further, we multiple entity
-  > identifiers are used to refer to the same entity, then how do we
-  > reconcile them later?
-
-The example of "luc in boston" in January and June has been discussed extensively.
-Theroretically, we can find distinguishing attributes, yes (luc with winter clothes
-and summer clothes). But we have no requirements that these attributes are expressed.
-So, if we have just "luc in boston" as a characterization, the constraint makes sense.
-
-PM agreed
-
-  > 
-  > I believe this consideration is not required and adds a layer of complexity.
-  > 
-  > 5. A characterization interval may collapse into a single instant.
-  > 
-  > Issue: Are we referring to time values. We seem to be using terms like
-  > "characterization interval", "continuous interval", "single instant"
-  > etc. as surrogates for time. I suggest that we explicitly use "time"
-  > if all these other terms are not distinguishable from time.  
-
-Time is a can of worms, since we can have multiple clocks, not necessarily synchronised.
-
-That's why the whole model is event based.
-
-PM see my earlier comment. Satya has a point when he says events are "surrogates for time". 
-Have no solution, but need more discussion goinf forward. This issue will continue
-
-Luc: I think that's the other way round. Observable time is an approximation for events.