ISSUE-138: Collection does not describe multiple additions/replacements

collection-collision

Collection does not describe multiple additions/replacements

State:

CLOSED

Product:

prov-dm

Raised by:

Stian Soiland-Reyes

Opened on:

2011-10-29

Description:

http://www.w3.org/TR/prov-dm/#expression-Collection introduces relations for expressing collection modifications:


Expression: wasAddedTo_Key(c,k) (resp. wasRemovedFrom_Key(c,k)) denotes that collection c had a new value with key k added to (resp. removed from) it.


It is not clear what would happen if a second addition added a value with the same key.

Imagine:

wasAddedTo_Coll(c2,c1)
wasAddedTo_Key(c2,k1)
wasAddedTo_Entity(c2,e1)

wasAddedTo_Coll(c3,c2)
wasAddedTo_Key(c3,k1)
wasAddedTo_Entity(c3,e2)

It is clear that c3 contains (k1, e2). Does it also contain (k1, e1)?

I understand this is meant as a general collection, and the interpretation of this might as well depend on the specific type of collection. However that means that without knowing the type of collection you can't tell if e1 is contained in c3 or not.


I believe we should not allow automatic replacement, and neither allow multiple values for the same key. So if asserting:

wasAddedTo_Coll(c2,c1)
wasAddedTo_Key(c2,k1)
wasAddedTo_Entity(c2,e1)


c1 does *not* contain k1, but *might* have e1 under a different key.


Suggested:
wasAddedTo_Coll(c2,c1); wasAddedTo_Key(c2,k1) asserts that c2 now contains the key k1 - but the collection c2 is derived from, c1, did not contain the key k1.

A second addition of the same key without an intermediate removal is not valid in PROV. If the specific type of collection is performing replacement by key, such as a dictionary/map/hashtable, then the asserter will need to model an intermediate wasRemovedFrom_Coll(intermediate, original) and wasAddedTo_Coll(new, intermediate). If the specific type of collection contains multiple values per key, then the value should instead be asserted as a new nested collection of those values.

Related Actions Items:

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Related emails:

1. Re: PROV-ISSUE-136 (collection-functional): Collection not stated as functional [Data Model] (from soiland-reyes@cs.manchester.ac.uk on 2012-04-25)
2. Re: closing old collection issues -> the question of monotonicity of provenance (from Paolo.Missier@ncl.ac.uk on 2012-03-29)
3. Re: closing old collection issues (from soiland-reyes@cs.manchester.ac.uk on 2012-03-29)
4. Re: closing old collection issues (from L.Moreau@ecs.soton.ac.uk on 2012-03-28)
5. Re: closing old collection issues (from satya.sahoo@case.edu on 2012-03-28)
6. Re: closing old collection issues (from L.Moreau@ecs.soton.ac.uk on 2012-03-28)
7. closing old collection issues (from Paolo.Missier@ncl.ac.uk on 2012-03-28)
8. Re: PROV-ISSUE-138 (collection-collision): Collection does not describe multiple additions/replacements [Data Model] (from soiland-reyes@cs.manchester.ac.uk on 2012-02-22)
9. Re: PROV-ISSUE-136 (collection-functional): Collection not stated as functional [Data Model] (from soiland-reyes@cs.manchester.ac.uk on 2012-02-22)
10. PROV-ISSUE-138 (collection-collision): Collection does not describe multiple additions/replacements [Data Model] (from sysbot+tracker@w3.org on 2011-10-29)

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