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PROV-ISSUE-4: agent subtypes?

From: Luc Moreau <L.Moreau@ecs.soton.ac.uk>
Date: Thu, 14 Jul 2011 16:21:23 +0100
Message-ID: <EMEW3|c3366f9cd06eddee1fe6e227e99721bbn6DGLQ08L.Moreau|ecs.soton.ac.uk|4E1F0973.1000204@ecs.soton.ac.uk>
To: public-prov-wg@w3.org
Hi Reza,

Yes, it's a good idea to discuss agent subtypes as a separate thread.

 From my point of view, I want to be sure that we don't disallow some 
kind of agents, simply
because we had not thought about them.

I believe that from a biology/chemistry point of view, a catalyst could 
be seen as an agent.

Views on this?


On 07/13/2011 07:41 PM, Reza B'Far wrote:
> Graham -
> Thank you for your thorough response. Please note the following:
>    1. I'm completely fine with sub-typing.  As long as the more
>       concrete types (some more exact definitions of agent) are
>       available, I'm fine with them "inheriting" from more generic
>       types.  My chief concern as an implementer is to make sure that
>       there is enough "typing" available so that there is no loss of
>       data in the export/import process that can be avoided. _*So, is
>       the next step creation of a new email thread for sub-typing Agent?*_
> On 7/12/11 11:48 PM, Graham Klyne wrote:
>> Reza,
>> I have two main responses to your comments:
>> (1) your description of "Agent" here seems to me to be closer to what 
>> the provenance work has envisaged than that described in ws-arch 
>> document mentioned by Ryan.
>> (2) I fully accept your need for volitional vs computational agent 
>> distinction for establishing certain kinds of trust in data.  But I 
>> still think that a generic agent class would keep things simpler for 
>> developers who are not so concerned with specific legislative or 
>> similar frameworks - I think it's easier to subclass a generic class 
>> as needed than to unite distinct classes.
>> Given that yours is a concrete use-case addressing a real and 
>> immediate implementation need (I understand from comments by you and 
>> your colleague) I think it may be appropriate to include this 
>> person-vs-program distinction of agents in an initial model, but also 
>> providing a generic agent superclass for implementations that don't 
>> care or don't know what kind of agent is involved.
>> ...
>> Also, I note that even in my revised understanding per your comments, 
>> the provenance notion of "process execution" still isn't covered by 
>> the ws-arch terminology relating to agency.
>> ...
>> You mentioned PACE.  The matter of the relationship between work in 
>> provenance and work in trusted systems came up in the telecon to 
>> review work of the provenance incubator group, led by Yolanda Gil.  
>> The point she made there was that [while these are clearly 
>> interconnected] the trust work has focused on trust in *systems*, 
>> where the provenance work is concerned with establishing credibility 
>> in specific datasets.  To this extent, I think we need to be cautious 
>> about over-extending the provenance model to also include concepts 
>> that would propoerly belong in a model for trusted systems.
>> #g
>> -- 
>> Reza B'Far wrote:
>>>    Folks -
>>> To add to Ryan's comments, I had put in a comment previously 
>>> regarding using stronger types for agents.  From a practical 
>>> implementation perspective, a subset of which Ryan mentions to be 
>>> "audit" trail, etc., please note the following -
>>>    1. The distinction between the direct intervention of a human being
>>>       effecting the state of a data versus an indirect intervention is
>>>       absolutely crucial.  Without this, establishing "trust" (I mean
>>>       this from a formal perspective - something like PACE[1])
>>>    2. I personally would lean towards one of the following options -
>>>           * Strong Typing of the Agent to multiple types and specifying
>>>             exactly what we mean by the types.  For example, /Human
>>>             Agent, System Agent/, etc.  I've mentioned this in a
>>>             previous thread.  Within all practical usages of provenance
>>>             that at least I'm concerned with, there are completely
>>>             different treatments of a "snapshot" (or whatever you want
>>>             to call it) of the state of an entity (which would be
>>>             considered something that is included in provenance) based
>>>             on whether or not there is direct human intervention (or
>>>             alternatively, far more specification and strong typing) of
>>>             the changes.  "Agent" is way to generic to be useful
>>>             practically.
>>>           * Reducing the use-cases of Agent to just User-Agent which is
>>>             the approach that is used in some of the other W3C 
>>> standards
>>>             and is weaved into the fabric of www as we know today.  
>>> This
>>>             would reduce the scope of what an "Agent" is.  We may
>>>             possibly be able to leverage work of UAProf[2] and even if
>>>             not, we can learn from UAProf and CC/PP as examples.
>>>    3. The key of both (1) and (2) above is that we in order to have a
>>>       practical implementation, it is highly desirable to have some 
>>> very
>>>       exact meaning for what "Agent" is, what it does, what the 
>>> boundary
>>>       conditions are, etc.  I also highly encourage that we do NOT
>>>       include concepts that start going into RBAC and other security
>>>       related standards such as Role.  IMO, we need to reuse concepts
>>>       from these standards.
>>> I'm relatively new to the group, but have spent a lot of time 
>>> reading the archives.  From an implementation perspective, I caution 
>>> that if things are too generic and there is not enough specification 
>>> (typing) and exactness in order to accommodate a larger tent, there 
>>> may be long term implementation hurdles that are presented in terms 
>>> of practical implementation.  In terms of a specific example, I 
>>> think "Agent" above is one.  It's far too generically defined at 
>>> this point, IMO.
>>> Please see references below.
>>> [1] - PACE - 
>>> http://citeseerx.ist.psu.edu/viewdoc/summary?doi=, 
>>> http://www.mendeley.com/research/architectural-support-trust-models-decentralized-applications/ 
>>> [2] - UAProf - http://en.wikipedia.org/wiki/UAProf
>>> [3] - CC/PP - http://www.w3.org/Mobile/CCPP/
>>> On 7/12/11 12:17 PM, Graham Klyne wrote:
>>>> Ryan,
>>>> I think the important element that is missing is that provenance as 
>>>> understood so far by this group is intended to capture actual 
>>>> rather than potential or unrealized processes.  This is the idea 
>>>> that "Process execution" aims to capture.  The notion of "Agent" as 
>>>> described by the ws-arch spec is, to my mind, very much concerned 
>>>> with the potential rather than the realized computation.
>>>> Although I'm not a long-time expert in this field, I think this is 
>>>> quite central to the notion of provenance we're trying to 
>>>> articulate and record, so it's an area where the terminology needs 
>>>> to be quite distinct from other usages.  You usage of "invocation" 
>>>> comes closer, I think, but I'm not convinced that yet another new 
>>>> term (it's not covered in ws-arch as I recall) is helpful at this 
>>>> stage.
>>>> Because of the focus on actual computations, there's 
>>>> correspondingly less need (or so it seems so far based on the 
>>>> use-cases considered) to consider subteties of potential processes 
>>>> ("Recipes", "Roles", etc.).  I remain open on this, but I would 
>>>> avoid adding concepts for which there is not demonstrated need 
>>>> within the goals of provenance modelling and recording.
>>>> #g
>>>> -- 
>>>> Ryan Golden wrote:
>>>>> Thanks for taking a look at this, Graham, and I'd be interested to 
>>>>> hear more feedback from others.  To address a couple of your 
>>>>> comments:
>>>>> My intent with Agent was that it closely resemble the concept of 
>>>>> Invocation, as you say.  I suppose the language "is a 
>>>>> computational entity" does not effectively convey the intention.  
>>>>> I think Invocation necessarily implies an Invoker, so I chose a 
>>>>> similar but broader concept of Realization.  How does does this 
>>>>> strike you as a replacement for Process Execution?
>>>>>     An Agent realizes zero or more Roles on behalf of zero or more 
>>>>> Persons or Organizations."
>>>>> My intention with Role is to broaden the idea of Recipe to include 
>>>>> more abstract functions and purposes, but also to add a subtle 
>>>>> implication (though not requirement) that it is something to be 
>>>>> realized on behalf of a person or organization.
>>>>> In associating Person or Organization to the concepts of Agent and 
>>>>> Role, the model comes closer to something that would be useful in 
>>>>> representing audit trails or in establishing the trustworthiness 
>>>>> of provenance assertions.
>>>>> --Ryan
>>>>> On 7/12/2011 10:00 AM, Graham Klyne wrote:
>>>>>> (ref. W3C Web Services Architecture Note 
>>>>>> <http://www.w3.org/TR/ws-arch>)
>>>>>> Notwithstanding the slightly divergent usage in the provenance 
>>>>>> research community, I think there is value in using terms already 
>>>>>> adopted in the web services community where they align - I think 
>>>>>> that would help to make our outputs be more readily accepted, 
>>>>>> hence more relevant.  Thus, I think "Person or Organization" is 
>>>>>> reasonable term, replacing (as I understand) what provenance 
>>>>>> efforts have described as "Agent".
>>>>>> But my understanding is that "Process execution" is *not* the 
>>>>>> same as ws-arch:"Agent", being intended to reflect a specific 
>>>>>> invocation of the programme or service.  I think the term 
>>>>>> ws-arch:"Agent" would more closely replace "Recipe".
>>>>>> I'm not sure "Role" (ws-arch:"Service Role") has a direct 
>>>>>> correspondence in the terms we've discussed to date, though there 
>>>>>> is a notion of something like role in OPM.  Similarly for 
>>>>>> "Realizes" and "Acts on Behalf of".
>>>>>> #g
>>>>>> -- 
>>>>>> Ryan Golden wrote:
>>>>>>>    I'd like to bring a proposal up for discussion regarding 
>>>>>>> Process Execution and its related concepts.  Although at the 
>>>>>>> F2F1 there wasn't much discussion over "Process Execution," 
>>>>>>> "Generates," "Uses," and "Agent," I believe more clarification 
>>>>>>> and discussion is needed in these areas.
>>>>>>> High Level Proposal
>>>>>>> ----------------------------
>>>>>>> a) Rename the concept of "Process Execution" to "Agent," 
>>>>>>> adjusting/adding a few properties
>>>>>>> b) Rename the concept of "Process/Recipe" to "Role," 
>>>>>>> adjusting/adding a few properties
>>>>>>> c) Add the concept of "Person or Organization"
>>>>>>> d) Add the concept of "Realizes"
>>>>>>> e) Add the concept of "Acts on Behalf of"
>>>>>>> More Detailed Proposal
>>>>>>> ---------------------------------
>>>>>>> a) Concept: Agent
>>>>>>>     - is a computational entity (narrowed from "piece of work")
>>>>>>>     - may use zero or more Entity States (Bobs)
>>>>>>>     - may generate zero or more Entity States  (Bobs)
>>>>>>>     - may realize zero or more Roles
>>>>>>>     - may have a duration
>>>>>>>     - may acts on behalf of a "Person or Organization"
>>>>>>>     Discussion:
>>>>>>>         Agent is a relatively well-defined industry term for an 
>>>>>>> program acting on a user's behalf.   I propose it as a 
>>>>>>> replacement for "Process Execution," which has the overloaded 
>>>>>>> (and thus undesireable) term "process" in it, and does not 
>>>>>>> necessarily imply that it is acting on behalf of any one person 
>>>>>>> or organization.  In scenarios involving trust, audit, or change 
>>>>>>> tracking, the ability to identify the "who" is crucial, and so 
>>>>>>> the relation between Agent and Person or Organization is 
>>>>>>> introduced.  "Person or Organization" is discussed further 
>>>>>>> below.         Some other common variations are "software 
>>>>>>> agent," or "user agent."  One notable difference between this 
>>>>>>> concept and other agent concepts is that our Agent may have a 
>>>>>>> duration.  I'm still undecided on the utility of the duration.
>>>>>>>         There will be some discussion here about 
>>>>>>> non-computational agents.  I would question the utility of being 
>>>>>>> able to assert relations involving Entity States (Bobs) and 
>>>>>>> non-computational agents, and would ask you to first consider 
>>>>>>> whether the same semantics could be better represented by a Role 
>>>>>>> instead [see next].
>>>>>>> b) Concept: Role
>>>>>>>     - is an abstract set of tasks which pertain to a job function
>>>>>>>     - may have semantics beyond the scope of the WG model (e.g., 
>>>>>>> as described in the RBAC reference model)
>>>>>>>     - may be realized by zero or more Agents        Discussion:
>>>>>>>         Replaces the somewhat confused notions of "Agent" (as it 
>>>>>>> was discussed at F2F1), "Process," and "Recipe".  Note that 
>>>>>>> multiple Roles can be realized by a single Agent.
>>>>>>> c) Concept: Person or Organization
>>>>>>>     - is a real-world person or organization that an Agent acts 
>>>>>>> on behalf of
>>>>>>> d) Concept: Realizes
>>>>>>>     [see Agent and Role]
>>>>>>> e) Concept: Acts on Behalf of
>>>>>>>     [see Agent and Person or Organization]
>>>>>>> References:
>>>>>>> I have adapted some of this proposal from concepts in the W3C 
>>>>>>> Web Services Architecture Note <http://www.w3.org/TR/ws-arch>, a 
>>>>>>> document that I don't entirely agree with, but which has some 
>>>>>>> useful models in it. I also referred to the NIST RBAC reference 
>>>>>>> model.

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 Thursday, 14 July 2011 15:22:03 UTC

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