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Re: PROV-ISSUE-187: Section 5.2.2 (PROV-DM as on Nov 28) [prov-dm]

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Mon, 13 Feb 2012 08:09:55 +0000
Message-ID: <EMEW3|1e2cea4154217139532ec1de4223f38co1C89v08L.Moreau|ecs.soton.ac.uk|4F38C553.50807@ecs.soton.ac.uk>
To: public-prov-wg@w3.org
Hi Paul and Satya,

I agree with Paul, 'Literal' was the focus of ISSUE-142, which has now 
been closed.

Luc

On 02/12/2012 06:43 PM, Paul Groth wrote:
> Hi Satya,
>
> It's important to recognize that a prov:Literal is *not* an OWL2 
> literal. Mixing these two things leads to confusion.
>
> prov:Literal as the DM states can support IRIs. I think the DM purpose 
> is letting different serializations decide how they want to encode 
> types in their type system and thus is being agnostic.
>
> I guess, my conclusion is that it's perfectly fine to map prov:type to 
> rdf:type in the PROV-O. Different serializations will adopt different 
> ways of mapping to the dm.
>
> cheers,
> Paul
>
>
>
> Satya Sahoo wrote:
>> Hi Luc,
>> My responses are interleaved:
>>
>>     Hi Satya,
>>     In addition to my previous response, please also see:
>>     
>> http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#dfn-type 
>>
>>     for definition of prov:type.
>>
>> The definition of prov:type "PROV-DM liberally defines a type as a
>> category of things having common characteristics." from DM TPWD is
>> definition of a "class" in knowledge representation/ontology. In other
>> words, prov:type is same as rdf:type, we are just using slightly
>> different words to describe it? Also, please consider that using
>> prov:type implicitly brings in the notion of distinguishing between
>> "class/category" and "instance/value" (TBox, ABox from DL) - is that
>> what you and Paolo have in mind for DM?
>>
>>
>> Also, "only states that the value associated with a prov:type attribute
>> /must/ be conformant with Literal." is using same words as OWL2 Literal,
>> but misinterpreting the construct. OWL2 Literal maps to specific
>> datatypes (described in Section 4 of OWL2 syntax
>> (http://www.w3.org/TR/2009/REC-owl2-syntax-20091027/#Datatype_Maps),
>> which are primarily XSD datatypes. I am not sure how prov:type
>> conforming to Literal can be used to link a specific value to a category
>> for that value (a Class in other words) - a Class/category is not a XSD
>> datatype value? I believe this constraint should be removed.
>>
>>
>>     Luc
>>
>>     On 08/12/11 09:17, Luc Moreau wrote:
>>>     Hi Satya,
>>>     Comments interleaved.
>>>
>>>     On 12/08/2011 01:38 AM, Satya Sahoo wrote:
>>>>     Hi Luc,
>>>>     Apologies for my delayed reply to your earlier mail. I have
>>>>     responded to your comments in ISSUE 101.
>>>>
>>>>     One response is interleaved:
>>>>
>>>>         To address this specific example, I am not sure what you are
>>>>         trying to express, since the attribute status
>>>>         is application specific. But for example, you could write
>>>>
>>>>         activity(a1, [status="composing text", status="uploading
>>>>         attachment", status="sending", status="sent"])
>>>>
>>>>         meaning that the activity a1 had a status with one of the
>>>>         possible values "composing ...", "uploading", ..." sent".
>>>>
>>>>
>>>>     Ok, so the values of an attribute can be assigned from a list of
>>>>     possible values? Then the current requirement that attribute
>>>>     values have to hold "...for its whole duration..." is not a
>>>>     requirement.
>>>
>>>     This is actually a good example to develop. Imagine that the
>>>     activity also had an extra status value: status="spellchecking",
>>>     but we don't include it in the activity record.
>>>
>>>     In such a case, a record such as
>>>     activity(a1, [status="composing text", status="uploading
>>>     attachment", status="sending", status="sent"])
>>>
>>>     would not be valid, because during the duration of the activity,
>>>     there is a status "spellchecking" that is not represented.
>>
>> Why would it not be valid - given an open world assumption, one can
>> always add new information to a record?
>>
>> Thanks.
>>
>> Best,
>> Satya
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>>
>>>     This requirement of having attributes with given values is also
>>>     present in entities. The driver for this requirement is
>>>     that to be able to express provenance, we need something that is
>>>     fixed, from some perspective.
>>>
>>>
>>>     I propose to add this example to the document, and explain this.
>>>     Is this an appropriate course of action?
>>>
>>>>
>>>>         The duration is given by the interval between start and event.
>>>>
>>>>         To some extent, an entity interval or an activity interval
>>>>         are opaque, we just know that some attributes
>>>>         hold for the duration.
>>>>
>>>>         If you want to describe that something changes in an
>>>>         activity. Say it was on hostA, and then on hostB,
>>>>         then, you need to express this as two separate activities.
>>>>
>>>>
>>>>     I believe this is an application-dependent requirement whether an
>>>>     activity running on hostA is different or same when it is running
>>>>     on hostB. For example, a Tomcat daemon running on port8080 or
>>>>     port80 will be considered the same activity by a user browsing an
>>>>     online book store.
>>>>
>>>>         Likewise, if you want to say running, paused, running,
>>>>         you also have to have separate activities.
>>>>
>>>>
>>>>     In case of an OS, the thread will have the same process id across
>>>>     its different states.
>>>     We are digressing, is your point related to interval addressed?
>>>>
>>>>         What definition would you like to see for type?
>>>>         Intentionally, it's open ended, so that we don't constraint
>>>>         application to using specific typing approaches.
>>>>         Further information is also available in the type attribute in
>>>>         
>>>> http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html#record-attribute 
>>>>
>>>>
>>>>
>>>>     I raised the issue since it matches the rdf:type attribute
>>>>     already defined and well known in the Web community it will be a
>>>>     source of confusion prov:type vs. rdf:type. The example given in
>>>>     Section 5.5.1 does not clarify how to interpret it. If we want it
>>>>     to be open-ended, then do we need to make it a reserved DM 
>>>> attribute?
>>>
>>>     Fine, but we are not defining the mapping to rdf here, we are
>>>     defining prov-dm.
>>>     It seems perfectly reasonable to say that the prov-dm attribute
>>>     type is expressed by rdf:type in an rdf:serialization.
>>>
>>>     This said, not all typing systems involve classes (as understood
>>>     by rdf) and not all typing systems use URI to represent
>>>     types. That's why prov-dm just states that the value of a type
>>>     attribute is a prov-dm literal.
>>>
>>>     Luc
>>>>
>>>>     Thanks.
>>>>
>>>>     Best,
>>>>     Satya
>>>>
>>>>
>>>>
>>>>         Luc
>>>>
>>>>         On 12/07/2011 01:53 AM, Provenance Working Group Issue
>>>>         Tracker wrote:
>>>>
>>>>             PROV-ISSUE-187: Section 5.2.2 (PROV-DM as on Nov 28)
>>>>             [prov-dm]
>>>>
>>>>             http://www.w3.org/2011/prov/track/issues/187
>>>>
>>>>             Raised by: Satya Sahoo
>>>>             On product: prov-dm
>>>>
>>>>             Hi,
>>>>             The following are my comments on Section 5.2.2 of the
>>>>             PROV-DM as on Nov 28th 2011.
>>>>
>>>>             Section 5.2.2:
>>>>             1. "attributes: a set of attribute-value pairs [
>>>>             attr1=val1, ...], representing other attributes of this
>>>>             activity that hold for its whole duration."
>>>>             "an activity record's attribute remains constant for the
>>>>             duration of the activity it represents."
>>>>
>>>>             Comment: I have raised this issue before - why does the
>>>>             attribute values of an activity have to hold for its
>>>>             whole duration? Why is this constraint necessary or
>>>>             enforceable?
>>>>             If emailing is an activity a0 with attribute "status",
>>>>             then how do we represent [status="composing text"],
>>>>             [status="uploading attachment"], [status="sending"], and
>>>>             [status="sent"]?
>>>>             In addition, what does "duration" of activity mean - the
>>>>             time when it is "active" or between its "start event" and
>>>>             "end event"? What about "paused event"?
>>>>
>>>>             2. "The attribute type is a reserved attribute of
>>>>             PROV-DM, allowing for subtyping to be expressed."
>>>>
>>>>             Comment: Exact definition of "type" is absent?
>>>>
>>>>
>>>>             Thanks.
>>>>
>>>>             Best,
>>>>             Satya
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>         --
>>>>         Professor Luc Moreau
>>>>         Electronics and Computer Science tel: +44 23 8059 4487
>>>> <tel:%2B44%2023%208059%204487>
>>>>         University of Southampton fax: +44 23 8059 2865
>>>> <tel:%2B44%2023%208059%202865>
>>>>         Southampton SO17 1BJ email: l.moreau@ecs.soton.ac.uk
>>>> <mailto:l.moreau@ecs.soton.ac.uk>
>>>>         United Kingdom http://www.ecs.soton.ac.uk/~lavm
>>>> <http://www.ecs.soton.ac.uk/%7Elavm>
>>>>
>>>>
>>>>
>>>
>>>     --
>>>     Professor Luc Moreau
>>>     Electronics and Computer Science   tel:+44 23 8059 4487 
>>> <tel:%2B44%2023%208059%204487>
>>>     University of Southampton          fax:+44 23 8059 2865 
>>> <tel:%2B44%2023%208059%202865>
>>>     Southampton SO17 1BJ               
>>> email:l.moreau@ecs.soton.ac.uk <mailto:l.moreau@ecs.soton.ac.uk>
>>>     United Kingdomhttp://www.ecs.soton.ac.uk/~lavm 
>>> <http://www.ecs.soton.ac.uk/%7Elavm>
>>>
>>
>>
>

-- 
Professor Luc Moreau
Electronics and Computer Science   tel:   +44 23 8059 4487
University of Southampton          fax:   +44 23 8059 2865
Southampton SO17 1BJ               email: l.moreau@ecs.soton.ac.uk
United Kingdom                     http://www.ecs.soton.ac.uk/~lavm
Received on Monday, 13 February 2012 08:10:21 GMT

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