[antlr-interest] EBNF - XML representations

[Ben Senior]

I'm new to this, but a few days ago I was asking on a different list 
whether anybody had a YACC description for parsing YACC... which is 
essentially what you're looking for I think?

Your goal is to parse arbitrary grammars in order to be able to reflect 
upon their structure (that XML is your desired output format, enabling 
to use some of it's common 'tool chain' is more or less irrelevant in 
this case)?

I'm not sure it is difficult at all to build a grammar for parsing 
grammars, I am just less convinced as time goes by whether that's a 
really useful thing to do.

It's all very well knowing how rules are related (these are the kinds of 
things ANTLRWorks excels at showing anyway) but most of the time what 
would be really useful is to be able to get better access to the state 
of the living breathing compiler ( a beast whose only real description 
is the pushdown state machine, whose state is then intimately connected 
to where you happen to be in your inputs).  For that, somebody here 
recommended XTEXT.

I do, however, agree that the way grammars are described (and work) 
seems not to have been designed to make it easy for meta-grammars (I 
don't know how else to put it, I'm afraid I'm still too green to know 
the vocabulary here :-) )

B

On 24/04/2011 02:42, Hans-Juergen Rennau wrote:
> Hi YY,
>
> to respond to your wondering: there is no primary task requiring an XML
> representation of grammars. It occurred to me when noticing that the official
> JPQL grammar references rules that do not exist, and that an XML representation
> would allow to detect such things with a simple XQuery expression, a one-liner,
> with mathematical precision.
>
> It seems to me there is an irony in the fact that a grammar - artefact meant to
> map syntax to logical structure - is so deeply steeped in syntax itself. This is
> no criticsm, just stirring my curiosity. The terseness and expressiveness of
> EBNF is indispensible, but perhaps we should have the possibility to switch back
> and forth between the terse and an XML representation? XML is a way to present
> logical structure in pure form (I am sure you agree - the angle brackets etc.
> are only the serialization format, not the thing "itself", which is a tree of
> information items), which enables operations on the information, operations
> whose precision, aggregative nature and conciseness are difficult to attain in
> any other way. I consider this example: let there be two grammars, which differ
> in respect to embedded actions, but not in respect to rule references. If we
> have an XML representation of the grammar available, this relationship can be
> revealed with few lines of XSLT or XQuery code, but how else? I am really
> curious. An attempt to to it with a filtering parser which filters out actions
> is, in comparison, much more work to achieve and also less clear in its results,
> more in need of an interpretation ("yes, the equality of the two token streams
> (resulting from the filtering) implies that the two grammars are equal in
> respect to the rule - token reference - structure"). XML allows to express such
> relationships rather explicitly and very tersely. Another example would be the
> possibility to detect equivalence of rules in spite of different choices of rule
> names. I imagine that such relationships may be important when trying to
> integrate work from different sources, or relating own work to existing work.  
>
> Cheers,
> -- Hans-Juergen
>
> ~~~
>
> Hi,
>
> I had a similar thought myself that this could be very handy while
> jumping into the markup realm.
>
> XML itself is described using an adaptation of EBNF. There is also a
> respective ISO standard for EBNF.
> But I am unaware of any XML (markup) representation of ENBF syntax. I
> believe it is not so complicated to produce a XSD for this and s.o.
>
> I wonder if there is any primary task you are urgent to solve with
> this besides satisfying own transformation joy?
>
>
> On Thu, Apr 21, 2011 at 10:55 AM, Hans-Juergen Rennau<hrennau at yahoo.de>  wrote:
>> Hello People,
>>
>> is there a translator which transforms an EBNF document into an XML
>> representation? And... is there a standardized XML representation of EBNF
>> grammers?
>>
>> The reason for my question: such a representation might enable to write tools
>> creating "grammer reports" with little effort and high precision, e.g. using
>> XSLT 2.0 or XQuery. (Example for such reporting: "show for each rule the rules
>> directly or indirectly referencing this rule".) And it might be a very
>> appropriate source for generating configurable "standard" transformations into
>> ANTLR grammers, or so I think at least.
>>
>> Kind regards from
>> -- Hans-Juergen
>>
>>
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>
>