[SCL] Re: Report on Common Logic

[pat hayes]

>Murray,
>
>I agree with Pat that we have to get a document finished
>by Dec. 17th

I did not say that and do not agree with it. It would be desireable 
but it is not an absolute necessity.

>and the version of the semantics posted on the
>CL web site is an adequate basis for that.
>
>>Are things actually stable enough for that yet? Don't questions
>>about seqvars have to be answered definitively first? Are there
>>any other outstanding issues that you guys need to agree upon?
>
>We always fight about issues.  But we understand one another
>well enough that we can sit down and work with the other guy's
>semantics if we decide to do so.
>
>I'm the one who has been resisting seqvars for a long time,
>and I admit that I would prefer to see sequences defined as
>first-class entities.  But I can define a CG-like syntax for
>either version, and the same abstract syntax could be used as
>a basis for an XML version.  After we finish the Dec 17th
>document, we can take a look at other options, which would
>replace one well-defined version of the semantics by another
>equally well-defined version.  Both versions would map to
>concrete syntaxes in a way that most casual users would not
>even notice a difference.

We have not discussed this option in the group, and I do not like the 
sound of it. The whole point of the SCL proposal is to have a single 
central model theory attached to the abstract syntax. HOwever, if 
your point is that this makes no difference to he XML, I would agree 
with that.

>
>>After that's done, an XML syntax still isn't completely
>>straightforward. Like any language, you need to decide exactly
>>what you're trying to do with it. Just *one* of the questions
>>I brought up early on was "web-enabled" or not? Use of URIs or
>>not? Any extensibility, so it can be the basis of other languages?
>
>Those answers were decided long ago:  web enabled, yes;
>URLs, yes; extensibility, yes; and basis for most common
>declarative languages, yes.

Wait: when was that decided? To create a web-enabled syntax is indeed 
one goal, but not the immediate one (ie aiming at Dec 17); the aim 
there should be a basic SCL-XML exporting syntax allowing SCL to be 
ported through an XML pipe, with the minimum of bells and whistles. 
URLs are permitted but not obligatory (as in SCL generally) and I do 
not feel that the XML syntax should be particularly extendable or 
web-enabled (whatever that means, it requires a lot more discussion): 
SCL is itself extendable, but there is no need to provide for 
extensions in (this) XML syntax: any extensions would be changes to 
the syntax and hence to the XML. So my answers (in the short term) 
would be:
web enabled, no; URLs are used but not mandatory; extensibility, no. 
I realize this makes it into a very boring exercise for an XML/web 
expert, but that is what we need done by the 17th (actually by about 
the 12th).

>
>>Does it have to be RDF-based, or can it be a new language?

No, it should not be RDF-based. That is a different project.

>
>The RDF triple-style is too restrictive to support full CL.
>But the RDF triples can be adopted as a subset of CLML, which
>would need a more general syntax to support full FOL.
>
>>If there's to be an XML version of CL, a list of requirements
>>should be the first thing created, which, if you remember, was
>>the first part of the XCL proposal I created way back when, in
>>the section on "Design Goals":
>
>Two important requirements:  support full CL, and support
>the RDF subset.

Why is the second not subsumed by the first? If you have some other 
sense of 'support' in mind for RDF, please be tiresomely clear about 
what it is.

>  Whether the OWL subset can be supported
>in the OWL notation is not clear, since the full FOL notation
>is much more general.  One option is to inlcude OWL as a
>redundant option, which could also be supported as a subset
>of the full notation for FOL.
>
>If you have a list of requirements, please send them
>to SCL list.
>
>>  ... Until then, there could be three or four or
>>more XML grammars that would "do" CL. First question is, what do you
>>really want from an XML version? Hopefully not just to be able to
>>say "there is an XML version." What are the goals?
>
>For political purposes, I regard the ability to say
>"There is an XML version" as extremely important.
>
>But as I have said in a note to CG list, I expect the N3
>notation to overtake the RDF notation as the most popular
>way of marking up web pages.  See the N3 primer:
>
>    http://www.w3.org/2000/10/swap/Primer
>
>As long as N3 is defined by a concrete syntax that conforms
>to the CL abstract syntax, I really don't care whether the
>programmers choose N3 or RDF (and I would bet that they are
>more likely to choose N3).

I presume you are referring to the XML rendering of RDF here.  N3 is 
written in RDF, which his defined by the RDF spec on a rather elegant 
graph-based syntax. I wish you were right about N3, but N3 has not 
been adopted as a W3 standard, has no stable definition and has a 
very small user community. The evidence seems to be that the world is 
adapting to the RDF/XML style. All extant OWL ontologies are written 
using RDF/XML, for example. One can of course use N3 as a surface 
notation for human readability: but then there are many other 
possibilities, such as Schreiber's UML-inspired OWL language or the 
exOWL graphical interface.

Pat
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