--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/model/working-copy/constraints-comments-PM.txt	Thu Apr 19 11:54:22 2012 +0100
@@ -0,0 +1,65 @@
+General comments:
+
+much improved over the version before James' edits!
+
+1.
+
+I like the distinction:
+- constraints that define validity, and
+- inferences that express necessary conditions (if - then) and can be generative.
+- definitions, 
+which is now crisp (to me):  constraints do not add new provenance facts, inference rules (incl. definitions) do  (please correct if my understanding is wrong).
+
+Indeed one problem we had was that the uniqueness constraint for example was stated in terms of inference, i.e.
+  wasGeneratedBy(e,a1) and wasGeneratedBy(e,a2)  => a1 = a2.
+I am very pleased to see that it's gone away now. 
+
+
+
+2. 
+Is this an additional useful distinction?
+
+- deductive rules:  no new data is created. ex.: closure over a transitive relation
+- generative rules:: new data is created. Ex.: new IDs for elements that are known to exist although they are not asserted in the provenance instance
+
+this has a bearing on implementations of rules based on a deductive model, for example, which does not generate new assertions.
+
+for instance hte attribution-implication inference would not be implemented (in general, unless you make up new information for the relations that you infer, these rules are not safe).
+
+3.
+I am blissfully ignorant of logic terminology, but is "entailment" essentially equivalent to "inference" here?
+
+---
+More specific comments:
+
+- 1.2:  possibly reordering expressions  -> I don't think there is an order to expressions?  I always viewed it as a set (in fact, as an extensional DB)
+ 
+- sec 2 Def. of definition:
+
+defined_exp holds IF AND ONLY IF there exists a_1,..., a_m such that defining_exp_1 ... defining_exp_
+
+should we clarify that the consequent are a conjunction?  i.e., when used as a sufficient condition to derive defined_exp, all of the  defining_exp_i must hold.
+
+- 2.1: I have always been confused by the overloading of wasStartedBy, and wasStartedBy-definition reinforces that (unless this is a mistake that has alreasdy been spotted?) the different signature of wasStartedBy forces me to go and check definiitions, and then convince myself that it makes sense?
+
+- 2.2. "@@TODO: Could this be an inference? Does it imply that a1 is associated with all activities a2 is associated with?"
+
+I don't think so. Delegation should be on a per activity basis, right?
+
+
+- 2.3 "A revision needs to satisfy the following constraint"  
+   should be inference? so it's not "satisfy", either.  
+
+- 2.4 I think spec-transitive escapes the clean model I praise at the beginning :-)
+
+"For any entities e1, e2, IF specializationOf(e1,e2) and specializationOf(e2,e1) THEN e1 = e2."
+
+I think this can only be expressed as a constraint, because e1=e2 is undefined...
+so:  specializationOf(e1,e2) and specializationOf(e2,e1) where  e1 != e2 is invalid.
+
+ 
+
+
+ 
+
+