W3C home > Mailing lists > Public > public-prov-wg@w3.org > July 2011

Bobs, IVP and time intervals

From: Cresswell, Stephen <stephen.cresswell@tso.co.uk>
Date: Thu, 14 Jul 2011 15:51:25 +0100
Message-ID: <F22D0BFCDD4DDC44B92C4E24D751CB9357E25F@W3EXC017023.theso.co.uk>
To: "Provenance Working Group WG" <public-prov-wg@w3.org>
Sorry for creating noise here, but this question is hindering my
understanding of what a bob is.


Does a bob describe an entity over some continuous time interval?


Since time intervals are mentioned nowhere in the definition of bob, I
think that the answer is no.  


However, when I try to visualise a bob, or think about how to use bobs
in representing provenance, I'm always thinking of something which does
conceptually have a continuous time interval associated with it, even if
the time interval wouldn't be stated.  This does make a difference to
how bobs would be used.


Consider a provenance graph in which some entity starts in some state s,
is moved by a process execution to another state s', and then moved by a
further process execution back to state s.


If a bob doesn't have a time interval associated with it, then the two
occurrences of state s could be represented by the same bob, and that
might lead to a cyclic provenance graph.


If a bob does have a time interval associated with it, then the states s
(1st occurrence), s', s (2nd occurrence) would necessarily be
represented by 3 different bobs.


Similarly, the "B IVP of A" concept is much easier to understand if B is
considered to have a time interval which is within the time interval of


Whereas the concepts seem to me to be easier to understand in the
presence of time intervals, this is not how they are defined, so should
I be fighting the temptation to think of them that way?


Stephen Cresswell

Semantic Web Developer

The Stationery Office

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Received on Thursday, 14 July 2011 14:51:54 UTC

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