[kepler-dev] web service actor

[Shawn Bowers]

Edward A Lee wrote:

> Another interesting question is what
> sort of subtyping (if any) is supported. Can one schema
> be a subtype of another?  If we build a clean type system around
> schema, this would be a big contribution, I think...
> 
> Edward


Yes, there are notions of XML subtyping, but not usually for the same 
reason as, e.g., is done in programming languages.  One reason people in 
the database community are interested in subtyping is to find "good" 
relational representations for XML -- that is, subtyping is used as a 
way to rewrite schemas to find convenient relational schemas.

However, the classic notion of subtyping in programming languages 
doesn't otherwise pop up much for XML.  One reason is that XML is 
inherently "distributed."  Gven two schemas from different 
organizations, just because they have the same structure, or one is a 
subtype in terms of structure, there is absolutely no guarantee that 
these schemas have anything to do with each other.  The same is true if 
we also consider tag names (it may just be coincidence that some of the 
tag names are the same).  Because the schemas were developed 
independently, it would also be pretty unusual that even for otherwise 
identical schemas, that the tag names or structure *would* be the same.

For web services, unless they were "designed to fit", it also seems like 
it would be pretty rare that you would ever apply the subtyping rules 
and find outputs that were subtypes of inputs.


Shawn




> 
> 
> At 05:07 PM 2/25/2004 -0800, Bertram Ludaescher wrote:
> 
> 
>> Chad:
>>
>> I have some questions regarding the types of data going in and out of
>> a web service: In my understanding, web services describe the type of
>> their data mostly in XML Schema, and not as Java types.
>>
>> Since web services can be implemented in different languages, Java,
>> C#, PHP, Perl, Python, ... what is the purpose of adding Java types in
>> particular?
>>
>> Wouldn't it be better to use XML Schema types and/or Ptolemy types and
>> make them part of the Kepler type system?
>>
>> We just had a (heated!!) discussion here between Ilkay, Shawn, a local
>> web service guru (Jesus) and myself...
>>
>> Maybe we should have a phone conference on that tomorrow or so...
>>
>> Bertram
>>
>> >>>>> "CB" == Chad Berkley <berkley at nceas.ucsb.edu> writes:
>> CB>
>> CB> Hi Ilkay,
>> CB> I was just wondering how your progress is going on getting the web
>> CB> service actor to return objects (besides strings).  I now have a 
>> bunch
>> CB> of web services that make calls to GRASS that I would like to use in
>> CB> kepler.  All of these services return the same object
>> CB> (GrassReturnObject).  If you want or need some help getting that 
>> actor
>> CB> to work, I'd be glad to help.
>> CB>
>> CB> chad
>> CB>
>> CB> _______________________________________________
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> 
> 
> ------------
> Edward A. Lee, Professor
> 518 Cory Hall, UC Berkeley, Berkeley, CA 94720
> phone: 510-642-0455, fax: 510-642-2739
> eal at eecs.Berkeley.EDU, http://ptolemy.eecs.berkeley.edu/~eal