[SCL] Approach to a concrete syntax

[Murray Altheim]

pat hayes wrote:
>> Murray Altheim wrote:
[...]
>> In going from the strict, model-theoretic semantics of SCL into an
>> expression in XML,
> 
> No; look, we aren't doing that. None of us are doing that. The XML 
> syntax for SCL doesn't go FROM the model theory; it PRESERVES the model 
> theory by expressing the full syntactic structure of SCL. The 
> 'commonly-used' upside-down A's and so forth are completely irrelevant.  
> SCL has been designed so that its abstract syntax makes NO committment 
> to particular glyphs, character sequences, whatever. It doesn't even 
> require that the syntax be encodable as a sequence of character codes, 
> in fact: it could be encoded diagrammatically, or using sounds, or 
> abstract 9-dimensional structures in superstring theory: anything you 
> like; all that is required is that whatever the form used, it somehow 
> make the syntactic distinctions required by the abstract syntax salient; 
> it must be parsable as SCL. We don't want it to alter or adapt or extend 
> the SCL abstract syntax; we just want it to express it, and to do so 
> accurately, so that it can be a legal SCL language.

Pat, you take from one of my utterances one preposition ("from") and
incorrectly ascribe to my proposals some assumption of the XML syntax
making changes to the SCL model theory. I am not stupid. I understand
the difference between what you are calling an "abstract syntax" and
XML as one of many possible "concrete syntaxes". It's not a difficult
concept. I have an IQ larger than a mango. If you've read my email
messages to this list and skimmed through the XCL proposal [XCL] you
should see that I've repeatedly used language that states this. The
very first goal stated clearly in the XCL spec is that "XCL should be
compatible with CL" and:

   1.  XCL should conform to the CL abstract model, as expressed in
       the CL standard (when available).
   2. It should be a relatively straightforward process to convert
      core XCL documents to other CL concrete syntaxes.
   3. The core features of XCL syntax should have essentially the same
      expressive power as CL.

[read "CL" as "SCL" here.]

So even where I didn't use exactly the same language as you might
have ("abstract model" vs. "model theory"), it should seem fairly
clear that we have the same goals for an XML syntax.

> Now, your level 2 envisions a webbified version of SCL. I agree this is 
> a worthwhile goal, though rather more ambitious that our immediate one, 
> but I think we need to ask some serious questions first about what kind 
> of ways is a logical language going to be used on the Web. This is where 
> it might be useful to look at RDFs?OWL/DAML , without being too slavish, 
> in order to get a sense of what kinds of webbification are being 
> contemplated. Extending the basic logical structure of the language 
> isn't one of them; allowing things like importing, mutual referencing, 
> versioning of ontologies is; so is issues like how to trace logical 
> names to their 'source' and what that means exactly. So is how to 
> express that one ontology is restricted to a particular universe of 
> discourse, but the terminology it uses is being used in an ontology with 
> a larger or smaller universe of discourse.

Nothing I've proposed in XCL Level 2 in itself modifies the essential
model theory that would be in Level 1. All it does is alter the specific
syntax used to express it in a way that *could* be modified by other
people. And as I've said before, the reason I've proposed both a "Level 1"
and a "Level 2" at the same time is not to create some alternate model,
but to provide (in Level 2) a clear path between the core syntax and
one that is extendable. I repeat: I have not in either XCL Level 1 or
Level 2 designed a syntax *different* than the SCL model theory, I've
only in Level 2 *allowed others* to alter it.

Now, if my XCL proposal in reality doesn't match SCL, it is not by
intention but because I've not seen a stable SCL long enough and had
enough time to update my draft to match it, OR (and this is a distinct
and likely possibility) I didn't understand all the angles on the
design well enough to implement them correctly. But -- I have NEVER
expressed an intention to *alter* the SCL semantics in the delivered XCL
specifications, either Level 1 or 2, neither in email, on the phone,
or in the XCL proposal.

> That last one is a REAL problem that nobody is taking seriously enough 
> and arises immediately on the Web, and which we could maybe make some 
> genuine contribution to. For examp0le, suppose ontology A which is about 
> human beings wants to use a relation name R used and 'owned' by ontology 
> B which is about Americans. In B, something might be said about the 
> complement of R, meaning (but not saying explicitly) all Americans for 
> which R is false. In A, however, this needs to be uniformly qualified by 
> inserting the 'all Americans' qualifiation systematically, in order to 
> translate adequately between the ontologies. Now, it would be GREAT if 
> we could provide a notation for expressing that kind of 
> translation-between-universes as part of the importation (using URIs 
> which need to be dereferenced using HTTP protocols plus an SCL - 
> encompassing RDFS and OWL - XML MIME-type rule of interpretation, 
> perhaps?) when referring to an ontology but not when used as a relation 
> name.

Well, that sounds like a mapping problem. Topic Maps were designed to
solve exactly this kind of problem.

> Its not that Im against webbification or uninterested in it, but I don't 
> want it to mess with the aspects of SCL that we have got right, but 
> ignore the aspects of logic-on-the-web that really need urgent attention.

Perhaps I'm not parsing that sentence correctly. Do you differentiate
"webbication" and "logic-on-the-web" or consider them the same thing?

[...]
>> What I believe we can do with XML is treat that minimally. I'll
>> endeavour to fix up Chris' draft as promised, and also alter my
>> XCL Level 1 syntax to match his as closely as possible, with the
>> minor alterations I've proposed to Pat, and which are already
>> there but not as clear as could be.
> 
> Look, let me be blunt about this. Any XML syntax which alters the 
> logical syntax of the SCL abstract syntax in ANY way is unacceptable. 
> Minor alterations are just as destructive of the semantics as major 
> alterations.  If you feel that the SCL syntax should be extended or 
> altered, propose the alterations to the group and we can discuss them.  
> But in the final document, the XML/SCL syntax, like all the other 
> concrete syntaxes for SCL, *must* track the SCL abstract syntax exactly. 
> This is central to the entire project, and is not negotiable.

I sometimes feel you need to consider me as an antagonist. Where have
you gotten the idea that I've proposed an XML syntax that alters the
SCL abstract syntax? In every case where I've suggested things like
general quantifiers, I've done so as a *potential extension* to the
base XML syntax, not as the delivered XCL specification. I've made
the kinds of proposals I've made to *enable* those kinds of extensions,
not to propose that the delivered syntax *itself* have those extensions.

>> Then, following on from Level
>> 1 is XCL Level 2, a lexically-different but semantically
>> identical XML markup language. The only difference between Level
>> 1 and 2 in practice is that the latter is web-enabled, and may
>> form the basis of other forms of logic *without* requiring new
>> syntax. And any alterations in syntax will *hopefully* be with
>> only very minor changes. I can envision an extension that would
>> express the situational calculus with only a few small changes.
> 
> What situational calculus? (If you mean in the AI sense, its already 
> expressible as a first-order, and hence SCL, theory)

Forget the situational calculus for a moment. Did you not read in
that paragraph (and part of that paragraph you didn't quote above)
that what I've proposed is an *attempt* at a faithful rendition
of SCL-in-XML? Why not lay off the boogeyman bit -- I'm not trying
to alter first order logic -- and you guys can concentrate on getting
SCL right, and I'll stop asking penetrating questions and sit
quietly on the sidelines in my unthinking, non-conceptualizing way
and just write grammar rules.

>> Now, I don't claim to be a mathematician, but I'm pretty sure I
>> can pull this off. I do understand that Pat has little interest
>> in that, which is fine.
> 
> Actually I have a lot of interest in it, but I think I may have a 
> different long-term agenda. I take the W3C Semantic web standards 
> seriously - I don't exactly love them, but I take them seriously - 
> but have little to no interest in topic maps. [...]

I've not proposed a Topic Map solution. XCL is simple XML. If
I talk about Topic Maps, it's because I'm using them for my
own projects. The idea of using PSIs is something just as useful
to the RDF community. The only difference between PSIs and URIs
is that the former provides a reasonable publishing methodology
so that humans and computers can use them, whereas there is
nothing available from the W3C or anyone else that satisfies
this need (to my knowledge). If you want to think that PSIs have
nothing to do with Topic Maps, that would probably give Bernard
Vatant (chair of the OASIS Published Subjects TC) no grief.

 > I want to work with the W3C,
 > or at least on a converging tracks, not in opposition to them.

Well, we can certainly have different agendas. I don't take them so
seriously, but neither do I consider I'm working in opposition to
them. I am simply ignoring them. I don't consider anything I've
proposed so far to disable some potential convergence of technologies.
I'm sure some engineer could write an XCL-to-RDF or RDF-to-XCL
converter in XSLT in an afternoon. If you think the only thing
that is acceptable to the community you consider relevant is some
W3C RDF-based markup language, fine. I'm absolutely certain there's
enough money and interest to keep that going within its own
community. Little I say or do will have any effect on that. And
if this group doesn't have any interest in an XML syntax (i.e.,
a syntax that's not RDF-based), I'll probably still publish an
XCL spec. I think it's a good idea, and it's a free world, right?
If it is in the end ignored, fine.

In summary:

I don't find this approach to communication very productive. I
basically have expressed an interest in assisting in developing
an XML concrete syntax for CL/SCL. In return I seem to have been
turned into the markup boogeyman and asked to please sit in the
corner. I've not proposed anything except what I've called "SCL-
in-XML" and "SCL-on-the-Web", two concepts that I thought would
be straightforwardly easy to understand and noncontroversial. In
return for that I've had to continually defend myself, discuss
the merits of RDF vs. Topic Maps (which is pointless), be careful
not to ask too penetrating questions, etc.  I hate to say not to
look a gift horse in the mouth, but this horse is getting pretty
tired of bearing that load. I could be spending my time much more
productively either actually *designing* things for this project
or some other project, like my Ph.D. studies or my own papers.
Despite what might seem the case, arguing in email is one of my
*least* favourite activities, second only to cleaning the toilet.
I'd rather just get some productive work done.

Murray

...........................................................................
Murray Altheim                         http://kmi.open.ac.uk/people/murray/
Knowledge Media Institute
The Open University, Milton Keynes, Bucks, MK7 6AA, UK                    .

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