PROV-ISSUE-157 (TLebo): wasInformedBy's non-transitivity

PROV-ISSUE-157 (TLebo): wasInformedBy's non-transitivity

http://www.w3.org/2011/prov/track/issues/157

Raised by: Timothy Lebo
On product: 

The argument that wasInformedBy is not transitive is not clear and convincing.

1) Does the diagram correctly illustrate the assertions wasInformedBy(a2,a1) and wasInformedBy(a3,a2), and wasInformedBy(a3,a1)? There seems to be a lot of additional unstated assumptions that are embodied by the diagram beyond these three DM assertions.

2) It appears that the counterexample is using a "degenerate" situation, when the argument for non-transitivity can ALSO be made for activities following a more natural time flow (e.g., even when e2 is used AFTER e1 is generated). In this situation, we do not _know_ that the information in e2 is related to the information in e1 _in any way_.

3) There is a "Note: This relation to be simplified using wasStartedBy/wasEndedBy.". Could someone point me to the expected changes here? 


Thanks,
Tim


Reference:

 
http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#record-OrderingOfActivities :

"""
The relationship wasInformedBy is not transitive. Indeed, consider the records wasInformedBy(a2,a1) and wasInformedBy(a3,a2), the record wasInformedBy(a3,a1), may not necessarily hold, as illustrated by the following event line.

            ------  a1
             |
             e1         
             |
       -------  a2
        |
        e2        
        |
     -----  a3

The end in activity record identified by a3 precedes the start in activity record identified by a1, while interval for activity record a2 overlaps with each interval for a1 and a3, allowing information to flow (e1 and e2, respectively).
"""

Received on Monday, 21 November 2011 15:26:32 UTC