Re: Multiple inputs and multiple outputs

Yuzhong Qu wrote:

> [Monika Solanki wrote:]
> 
> 
>>Drew McDermott wrote:
>>
>>
>>>  [Yuzhong Qu" <yzqu@seu.edu.cn>]
>>>  As we know, a process in DAML-S can have multiple inputs and multiple (conditional)outputs.
>>>  (From http://www.daml.org/services/owl-s/1.0/Process.owl
>>>  http://www.daml.org/services/owl-s/0.9/Process.owl)
>>>
>>>  1. In the case of  multiple inputs
>>>
>>>      It seems to me that the process specified should take multiple
>>>      inputs satisfying corresponding type constraint.
>>>      Am I right?
>>>
>>>Yes.
>>>
>>>      But, how do you know the exact number of inputs? You just know
>>>      what you know, maybe there is another statement about a new
>>>      input (another input may be specified in other place) due to
>>>      the openness of the Semantic Web (it's not a closed world).
>>>
>>>Good point.  We really need a fixed list of inputs and another of outputs.
>>>[It would be interesting denial-of-service attack to tell a service
>>>that it needed another input and have it then stall because no one is
>>>supplying it. :)]
>>>
>>
>>Although this may be an interesting theoretical argument, I do not quite 
>>agree to the fact, that for a particular process,  there may be inputs 
>>which might not be visible and are needed. I do not even envisage such a 
>>condition, because the process model is not the only model that handles 
>>these parameters. Infact the process model is just an abstract 
>>representation. We have to remember that there is a grounding model as 
>>well, which will take care of these details.for concrete process 
>>execution. If the specification of these multiple inputs located at 
>>multiple places is made visible in the grounding, then I do not see any 
>>problem.
>>
>>More comments on this welcome.
> 
> 
> Yes, this is a theoretical issue, but it's about the principle. I insist on my point.
> 
> What would happen when an agent (e.g. an agent doing the matching job) just gets some part of the stuff?
> 
> As we know, every agent just gets what it can get, the agent can't make sure that it has captured all of the related  stuff (e.g. multiple input/output issue).
> 
> How could an agent make sure that it knows all of the related knowledge distributed over the Internet/world?  
> 
> In the realm of the Semantic Web, an agent just knows what it knows, so does the human being.

Yes, this is an important issue in principle.  Also, it's important for 
many kinds of knowledge on the Semantic Web, not just for services 
declarations.

I don't know the final answer, but I've always assumed in practice this 
would be handled as follows:

For a given type of problem (such as service invocation) adopt a "closed 
world" convention with respect to a namespace.  That is, simply assume 
that a given document at a given point in time contains all of the facts 
(property instances) directly pertaining to the objects declared in that 
document.

Also, if it is desired not to rely on an implicit close world 
assumption, simply make it explicit (although I'm not sure exactly how 
that would be expressed in OWL).

This would be a good question to bring up on www-rdf-logic or 
www-rdf-interest mailing list.

Regards,
David

Received on Monday, 29 September 2003 11:25:37 UTC