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RE: Where are the semantics in the semantic Web services?

From: Shi, Xuan <xshi@GEO.WVU.edu>
Date: Sun, 18 Sep 2005 16:05:52 -0400
Message-ID: <D81F456794C18B4DA3E2ABC47DBBEEF2094D5F@www.geo.wvu.edu>
To: "'Joachim Peer '" <joachim.peer@unisg.ch>, "Shi, Xuan" <xshi@GEO.WVU.edu>
Cc: "''www-ws@w3.org' '" <www-ws@w3.org>, "'www-ws-request@w3.org '" <www-ws-request@w3.org>, "Shi, Xuan" <xshi@GEO.WVU.edu>

Dear Dr. Peer:

Thanks very much for your time and kind attention to my questions. Actually
I am suspicious about the current research approaches for both SW and SWS.
According to the definition of "semantic" Web, "semantic" means
machine-processable, then Web service by default is already "semantic" as
it's just designed for machines but now it's criticized as "not" semantic! 

Since many people said SWS is SW + WS, then I think we can talk about
something of SW first. How can we design and define the ontology for color?
People just use the concept of color by default without defining a color
ontology, but actually a specific color like "black" can be defined in
different approaches:

RGB -> (0 0 0) vs. (0, 0, 0) and more ... 
CYMK -> 0% 0% 0% 100% 
HSV -> 0 0% 0% 
Natural Language -> Black 
Hexadecimal code -> 000000 

All of them has the same meaning while such like "Aqua" and "Cyan" produce
the same color (e.g. in hex code 00FFFF) or "Fuchsia" and "Magenta" produce
the same color (e.g. in hex code FF00FF).

Thus how can SW/OWL/RDF experts use OWL/RDF to define the ontology of color
that includes those different specifications and relationship? Since the
datatypes are limited within XML schema, even we have to define "color"
class as a subclass of "string" which looks ridiculous. In this typical
case, color is a class and all named/coded color can be the instances of the
color class. Or we can define "red" as a subclass of class "color" since we
can define many more different colors like "xxxxx red". 

I will be very grateful to you or any other people in this community if you
can provide any existing reference to a color ontology defintion. Your kind
attention and advice will be greatly appreciated.

Best regards,

Xuan
 

-----Original Message-----
From: Joachim Peer
To: Shi, Xuan
Cc: 'www-ws@w3.org'; www-ws-request@w3.org; Shi, Xuan
Sent: 9/17/05 5:09 AM
Subject: Re: Where are the semantics in the semantic Web services?

hi Xuan,

> I specially appreciate the "law of the semantic web" as he said by the

end
> of the paper "The more agreement there is, the less it is necessary to

have
> machine-processible semantics". I think it's the same to semantic Web
> services.
> 

My thinking of using "semantic Web services" is that we
- need to write down a sufficiently large part of the semantics of a 
service using some kind of well defined 'building blocks',
- that can be assembled using some form of 'semantic glue' to capture 
service semantics.

The building blocks are domain-specific terms defined in some kind of 
shared ontology (just ANY form of agreed data type definition, IMHO that

could even be plain XML DTDs),

The 'semantic glue' is a well defined (logic-based) language that allows

to take these terms to form sentences like:

"if the world state statisfies an instance of formula F1 before service 
execution, then the state will satisfy an instance of formula F2 after 
successful execution." 

- the formulas F1 and F2 refer to the agreed domain terms and eventually

combine them using some kind of logical connectors like AND, OR, NOT
etc. 
- by "instance of a formula" i refer to the fact that formulas may be 
partially or fully grounded by the input data of the client or the
output 
of the server (see [1] for details)

While I also agree with the "law" (or paradox? ;-) of the semantic web
as 
expressed above, i think that semantic Web services can provide added 
value if they provide a nice and usable form of 'semantic glue' that 
allows people to form statements using their agreed vocabulary. 
 
> Question 2 still is whether semantic Web technology (RDF/OWL) is 
suitable
> for semantic Web services? RDF/OWL are good at defining the "nouns"
not
> "verbs". We can define one object is a subclass of another object. But

how
> can we define one function is a subclass of another function? Such as
in
> OWL-S approach, "BookSelling" is a subclass of "SellingService" and
> "SellingService" is a subclass of the root ontology class "e_Service".

Do we
> need to find some other ways to define the relationship of "verbs"?

i am not sure if one really needs *verbs*. Personally,  i like the idea
of 
characterizing operations by describing the precondition state and the 
resulting effect state. I think the description (characterization) of 
states does not require verbs, because states are just static snapshots.


But of course, sometimes one would like to use some form of "past
passive 
participles" of verbs to describe effects, e.g. for an email sender 
service, one could be tempted to state that the post-execution state 
entails "sent_mail(m, from, to)" (which of course has its roots in the 
verb 'sending').

BTW - for the practical implementation of semantic Web services i have 
designed an XML based markup language called SESMA [1], which might be 
seen as a subset of OWL-S that is less generic than the latter (all a 
question of using the right tool for the job, personal preferences etc.)

i have implemeneted several running (protoype) systems using this
language 
(e.g. [2]), and feel that SESMA is at least very useful if one needs to 
come up with a service description quickly

cheers!
Joachim


[1] http://www.ai.sri.com/WSS2005/final-versions/WSS2005-Peer-Final.pdf
[2] http://elektra.mcm.unisg.ch/pbwsc/docs/eswc05jpeer.pdf
Received on Sunday, 18 September 2005 20:06:34 GMT

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