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

Re: PROV-ISSUE-30 (name-for-bob): What name do we use for the BOB construct? [Conceptual Model]

From: Paolo Missier <Paolo.Missier@ncl.ac.uk>
Date: Mon, 25 Jul 2011 17:39:01 +0100
Message-ID: <4E2D9C25.1070203@ncl.ac.uk>
To: public-prov-wg@w3.org
Khalid just managed to put "snapshot", "perspective" and "view" in the same sentence. I see this as a good sign :-)

So, having put in a good word earlier for a variation of "snapshot", I would like to go back for a moment to "view", as intended in 
the database sense.

As we all know a view is indeed a perspective on the underlying database, and it has two key characteristics:
- it projects out irrelevant attributes (out of a potentially unbounded number of them, as in our case)
- if you materialize a view, this materialization remains valid only as long as none of the attributes that it contains (those that 
matter to the view) change their value in the underlying DB. When that happens, you need to recompute the view (= create a new 
materialized view, at least conceptually).

Isn't that what BOBs do?

In PIL the database itself is made of "things" (in Luc's latest terminology as of today) that we can only talk about and partially 
reveal by creating (mutiple) views, each valid within some temporal window, which is defined by value change events in its attributes.

this also avoid the "frozen in time" connotation that snapshots have in several contexts.


  On 7/25/11 11:07 AM, Khalid Belhajjame wrote:
> On 25/07/2011 10:24, Luc Moreau wrote:
>> The problem with Snapshot (like state, etc), is that it is the
>> snapshot of an entity.
>> We just don't want to distinguish an entity from its state, or an
>> entity from its snapshot.
> On the other hand, Snapshot has the advantage of conveying the fact that
> it is a description from a certain perspective (view).
> khalid
>> Hence, using Entity avoids this problem.
>> Luc
>> On 07/25/2011 10:19 AM, Paul Groth wrote:
>>> I thought we were getting somewhere with snapshot.....
>>> I don't think ENTITY really captures the intuition behind a BOB. It's
>>> too general.
>>> thanks,
>>> Paul
>>> Luc Moreau wrote:
>>>> The word 'Entity' should also be considered for the construct BOB.
>>>> If we do so, the text 'characterized entity' should be replaced by
>>>> something else in the draft specification.
>>>> Why not 'thing'?
>>>> So, the text could become:
>>>>     Section 4.
>>>>     In the world (whether real or not), there are things, which can be
>>>> physical, digital, conceptual, or otherwise, and activities involving
>>>> things.
>>>>     Words such as thing or activity should be understood with their
>>>> informal meaning.
>>>>     This specification is concerned with characterized things, that is,
>>>> things and their situation in the world, as perceived by the asserter.
>>>>     Section 5.1
>>>>     An ENTITY represents an identifiable characterized thing.
>>>> Luc
>>>> On 07/24/2011 11:43 PM, Reza B'Far wrote:
>>>>> First, for the record Khalid was the person suggesting Snapshot :)
>>>>> The way I've seen snapshot used commercially, it's fairly consistent
>>>>> with the current definition of BOB.  There is some murkiness on both
>>>>> sides (how "snapshot" is used commercially and I think we're still
>>>>> iterating here on the definition of BOB, but may be that's close to be
>>>>> finalized).  However, I think they are close enough.  What I liked
>>>>> about "Snapshot" is that its intuitive and is used in several domains
>>>>> that I know of (content management, legal, configuration systems, and
>>>>> I've also seen use-cases in microfilm production by old-school
>>>>> librarians).  Also, I think "Snapshot" offers a huge advantage that
>>>>> it's neither explicitly linked to the entity nor its state.  And I
>>>>> know the distinction between entity vs. entity's state and how that's
>>>>> articulated has been in a lot of the discussions.  Using "Snapshot"
>>>>> sort of obsoletes that discussion.
>>>>> On 7/24/11 12:57 PM, Stephan Zednik wrote:
>>>>>> I am not partial to snapshot, partially because of the extensive
>>>>>> functional usage of the term.  I have always associated a snapshot
>>>>>> with a point in time, not a duration - but this may be an incorrect
>>>>>> association.
>>>>>> I am open to discussing it, but my initial inclination was negative
>>>>>> towards it.
>>>>>> Will we use the same definition as we have been using for BOB?
>>>>>> --Stephan
>>>>>> On Jul 24, 2011, at 9:52 AM, "Reza B'Far"<reza.bfar@oracle.com>
>>>>>> wrote:
>>>>>>> I second the term "Snapshot".  This term also has functional usage
>>>>>>> in several commercial application categories used within roughly the
>>>>>>> same meaning.
>>>>>>> On 7/24/11 3:45 AM, Khalid Belhajjame wrote:
>>>>>>>> Hi Stephan,
>>>>>>>> Given the example you gave in your previous email, I think that
>>>>>>>> "EntitySpanshot" or "Snapshot" should be fine, given that it
>>>>>>>> reflect the fact that it is a description of an entity that holds
>>>>>>>> for some period of time.
>>>>>>>> Do you agree?
>>>>>>>> khalid
>>>>>>>> On 23/07/2011 20:24, Stephan Zednik wrote:
>>>>>>>>> I do not feel that EntityInstance, EntityInstantiation, or
>>>>>>>>> InstantiatedEntity make sense for the book ownership scenario, or
>>>>>>>>> any scenario modeling the provenance of changes in characteristics
>>>>>>>>> of a physical object.
>>>>>>>>> To reiterate the example since I haven't committed it to a wiki
>>>>>>>>> page yet.  Book X is an entity that represents a real world
>>>>>>>>> object.  It can be put on a shelf, loaned to friends, damaged,
>>>>>>>>> and/or destroyed.  It has important characteristics (condition,
>>>>>>>>> ownership, location, etc) that may change over the life of the
>>>>>>>>> book.  We may want to represent the provenance of the book as a
>>>>>>>>> chain of ownership.
>>>>>>>>> |<----------------------------------------------------- Book X
>>>>>>>>> ----------------------------------------------------------------->|
>>>>>>>>> |<!------ Book X with owner A ---->|<----Book X with owner B
>>>>>>>>> ---->|<---- Book X with owner A --------->|
>>>>>>>>> If a book changes ownership, is the "book with changed ownership"
>>>>>>>>> a different EntityInstance?  A different InstantiatedEntity?  I
>>>>>>>>> don't think what we current call a BOB is an 'instance of'
>>>>>>>>> anything.  I think of it as a description of an entity that holds
>>>>>>>>> for some time period (not necessarily given) for which
>>>>>>>>> contextually important mutable characteristics of the the entity
>>>>>>>>> are held to be known.
>>>>>>>>> --Stephan
>>>>>>>>> On 7/22/2011 5:29 AM, Curt Tilmes wrote:
>>>>>>>>>> On 07/22/2011 03:43 AM, Khalid Belhajjame wrote:
>>>>>>>>>>> The term "Snapshot" was suggested some time ago, and it seems
>>>>>>>>>>> that
>>>>>>>>>>> several people did like it.
>>>>>>>>>>> We can also use the term "EntitySnapshot".
>>>>>>>>>> Following from snapshot:
>>>>>>>>>> EntityInstance
>>>>>>>>>> EntityInstantiation
>>>>>>>>>> InstantiatedEntity
>>>>>>>>>> Curt

-----------  ~oo~  --------------
Paolo Missier - Paolo.Missier@newcastle.ac.uk, pmissier@acm.org
School of Computing Science, Newcastle University,  UK
Received on Monday, 25 July 2011 16:39:42 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 16:50:57 UTC