Re: presenting data models in RIF

Gary Hallmark wrote:
> 
> 
> 
> Dave Reynolds wrote:
> 
>> Do rules themselves need to access the data model not just the data?
> 
> rules need access to data and relationships.  For example, I expect a 1 
> to many relationship between purchase orders and line items, and I 
> expect to be able to express a condition in a rule about a purchase 
> order and its related line items.

Sure that's the data, not the model. If the rule itself needed to check 
the range constraint of the relationship hasLineItem or check the 
cardinality constraint that would be model-level access.

> The rules I've seen in RIF access relations and frames, not XML data nor 
> RDF data nor Java data.  If I plan to interchange some rules in RIF and 
> a data model in an XML schema, I'd also need some mapping information 
> that shows some kind of correspondence between schema definitions and 
> frames and relations.  How do I "bind" frames and relations in RIF to 
> types and relationships in XML schema?  

Exactly. In the case of RDF we are proposing a single canonical mapping 
so that every RDF vocabulary uses the same mapping.

In the case of XMLSchema I would expect this to be done by schema 
annotation which is why I mentioned the SAWSDL spec a while back.

You *could* have a canonical default mapping for un-annotated XMLSchemas 
but that would likely either have to make some assumptions like striping 
which won't be satisfied by all XMLSchema documents or would produce 
counter-intuitive mapping results on some schemas.

> Given an element 
> "http://someplace/line-item" and another element "http://someplace/po" 
> that contains a sequence of 0 or more line-item elements, how do I write 
> rules about po/@num = 123 and its related line-items?  What are the 
> frames? slots? Association between po and its related line-items?

Whatever the schema said in its annotations.

If you don't have schema annotations then it would depend on whether we 
had a default mapping scheme.

If RIF doesn't define a default mapping schema for generic XML data then 
you either access it via XPath operators or you could use the RDF 
mapping. Assuming the data is striped then the RDF mapping which would 
give you something like:

    po1[rdf:type->eg:PO,
        eg:num->"123"
        eg:line-item->li1[rdf:type->eg:Line-item, ...]]

where po1 and li1 are gensym'ed identifiers (the skolem constants used 
to represent RDF bNodes).


So how is all this done at the moment. In the MISMO example is the data 
model exchanged via an XML Schema (plus human readable documentation) or 
is there some other machine readable model representation being used? 
How are the elements of that XML (or other) schema being mapped to 
predicates etc in the case of ILog, Oracle, JBossRules etc?

Dave
-- 
Hewlett-Packard Limited
Registered Office: Cain Road, Bracknell, Berks RG12 1HN
Registered No: 690597 England

>> In the case of semantic web applications then yes, but that's not a 
>> problem since RDFS/OWL are themselves encoded in RDF so an RDF access 
>> mechanism is sufficient.
>>
>> I haven't heard any use cases for accessing the model itself in the 
>> XML or object cases. Gary presented a case (car/lorry/vehicle) for 
>> there *being* a data model but the rules seemed to only need to 
>> consult the type of instances not the hierarchy or domain/range 
>> constraints themselves). I understood Paul to be saying that direct 
>> access to the schema from the rules would be unusual in the business 
>> rule setting.
>>
>>
>> As a way to make progress I would find it helpful to get more use 
>> cases from the commercial vendors on how data models are exchanged at 
>> the moment and why a new RIF data model interchange would help. Based 
>> on things like the URC document section on processing models I had 
>> been under the impression that the dominant approach, outside RDF/OWL, 
>> was to define the data model in XML Schema and don't really see how 
>> the existence of a new class hierarchy relation is of significant 
>> benefit in processing data defined in such a way.
>>
>> Dave
>>
>> [Unfortunately I won't be able to make the next telecon.]
> 
>

Received on Wednesday, 22 August 2007 08:09:47 UTC