Re: Glossary entry: Abstract syntax

Gerd Wagner wrote:
>> A syntax must account for how statements in a language 
>> are going to be specified, and need not account for things 
>> that are implied (ie not explicit) in the syntax.  
> 
> Sure, that's what you can do using MOF/UML metanodels.
>  
>> A meta-model as a model of a modeling language must account for all 
>> the things in a language that matter to tools, and need not account 
>> for everything in the syntax.
> 
> That's not true, I can't follow you. If you make a metamodel 
> to define a language, then you account for everything in the 
> (abstract/conceptual) syntax.

A meta model does not *need* to be a syntax, and that is one of the 
reasons why the progenitors of metamodeling invented a new word rather 
than just reusing "syntax" - a metamodel is something different. 
Often the difference is subtle, but I have seen plenty metamodels 
which are not syntaxes.

There is nothing wrong with a metamodel that does account for 
everything in the syntax, however, and some (apparently you as well) 
consider this a best practice.

*More importantly* even for that subset of metamodels that do account 
for everything in the syntax, they account for much more as well. 
This is the crucial point.

>> In syntax, you must be concerned with 
>> how a sort is defined.  In a metamodel, you don't need to represent 
>> that (you CAN, of course), but you must represent that a language 
>> element has a sort.
> 
> No, you need not represent that for constructs for which the
> syntax does not require it. In a rule metamodel a function
> need not have a sort. It will have a sort, though, in the 
> underlying vocabulary metamodel (which you still miss to 
> discuss, btw).

I have no idea what you're talking about.

>> The problem with using a metamodel as an abstract syntax is that you 
>> must identify the parts of the model that don't actually have a 
>> syntactic construct. 
> 
> Again, I can't follow you.

Nor I, you.

> 
>> So the UML diagrams you see for RIF are to be interpreted as visual 
>> representations of the syntax, such that a subclass is a syntactic 
>> disjunction an aggregation is syntactic concatenation, and 
>> multiplicity on aggregation is repetition.  The tools that will 
>> generate the XML and BNF syntax specifications for RIF from the asn06 
>> will use that assumption.
> 
> So, was there any decision to use Sandro's experimental "asn06"?

This decision was made at the Jan 30 telecon: we will maintain the RIF 
syntax as asn06.  We have not decided what to make normative, however. 
  "Maintaining the asn06 syntax" does not necessarily mean it will be 
the normative syntax.

> What about the objections of Francois, and my suggestion to use 
> the more mature framework of KM3/ATL? Are they just ignored?

Perhaps you are being a bit free with the word "objection" here, as it 
has a formal meaning in the W3C process.  I have seen no formal 
objections.  Can you be more specific?

At the f2f we did briefly discuss KM3, but your message was received 
during the meeting itself and we did not have time during the meeting 
proper to look at it.  In general, if you want to make comments to be 
considered during a meeting, you must make them in advance.  The f2f 
required reading list was already long a week before the meeting.  KM3 
nor any other kind of syntax will not impact the 1st WD.

However, this does not mean it, nor any of a host of other issues 
deferred to the next WD are being ignored.  If this issue is important 
to you, then continue to educate the group about it.  Most productive, 
for example, would be to propose an abstract syntax for the current 
RIF CORE modeled in KM3. Such an effort would ground any discussion in 
a way that would allow us to examine the tradeoffs and compare them 
("them' being asn06 and km).

Thanks,
Chris

-- 
Dr. Christopher A. Welty                    IBM Watson Research Center
+1.914.784.7055                             19 Skyline Dr.
cawelty@gmail.com                           Hawthorne, NY 10532
http://www.research.ibm.com/people/w/welty

Received on Friday, 9 March 2007 01:40:28 UTC