ISSUE-176: wasInformedBy's non-transitivity example is confusing
TLebo
wasInformedBy's non-transitivity example is confusing
- State:
- CLOSED
- Product:
- prov-dm
- Raised by:
- Timothy Lebo
- Opened on:
- 2011-12-02
- Description:
- ------ a1
|
e1
|
------- a2
|
e2
|
----- a3
This diagram is confusing and it does not convince me that wasInformedBy is not transitive.
In an attempt to decipher the example, I created the following diagram.
1) Does my diagram also provide an argument that wasInformedBy is not transitive?
2) Could some of the visual argument used in this diagram be applied to the example in DM?
Thank you for your consideration.
Regards,
Tim
http://dvcs.w3.org/hg/prov/raw-file/48af93cb1e1b/diagrams/activity-ordering-records-information-flow-ordering-not-transitive.png
- Related Actions Items:
- No related actions
- Related emails:
- Re: PROV-ISSUE-176 (TLebo): wasInformedBy's non-transitivity example is confusing [prov-dm] (from L.Moreau@ecs.soton.ac.uk on 2011-12-08)
- PROV-ISSUE-176 (TLebo): wasInformedBy's non-transitivity example is confusing [prov-dm] (from sysbot+tracker@w3.org on 2011-12-02)
Related notes:
The diagram http://dvcs.w3.org/hg/prov/raw-file/30f5ce6376c4/model/informedByNonTransitive.png and the description copied from DM are reasonable.
Thank you for the clarification.
"The relationship wasInformedBy is not transitive. Indeed, consider the following records.
wasInformedBy(a2,a1)
wasInformedBy(a3,a2)
We cannot infer wasInformedBy(a3,a1) from them. Indeed, from wasInformedBy(a2,a1), we know that there exists e1 such that e1 was generated by a1 and used by a2. Likewise, from wasInformedBy(a3,a2), we know that there exists e2 such that e2 was generated by a2 and used by a3. The following illustration shows a case where transitivity cannot hold. The horizontal axis represents time. We see that e1 was generated after e2 was used. Furthermore, the illustration also shows that a3 completes before a1. So it is impossible for a3 to have used an entity generated by a1."
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