[Monetdb-developers] XRPC syntax

Jens Teubner jens.teubner at in.tum.de
Fri Oct 27 12:40:28 CEST 2006


Hi Jennie, hi Peter,

I am currently looking into the XRPC syntax.  Primarily I wanted to give
you feedback to what you wrote in your Plan-X submission.

So you are defining the syntax to be

   XRPCCall ::= "execute" "at" URILiteral FunctionCall

Lateron, however, you allow more than just a literal URI, but rather an
XQuery expression.  So `URILiteral' is definitely wrong here.

Once you changed this to, say, ExprSingle, you end up with ambiguity in
your parser.  Consider

   execute at "foo" eq ("bar")

(I couldn't think of a better example ad hoc.)  What we have here is an
ambiguity: we don't know whether `eq' is supposed to be a function call,
or if it is the binary operator `eq', followed by another expression in
parenthesis.

So I will take the freedom to modify your syntax proposal and do it in a
more XQuery-like style:

   "execute" "at" "{" Expr "}" "{" FunctionCall "}"

This avoids the ambiguity and should make it rather easy to parse.

...already hacking...

Jens

-- 
Jens Teubner
Technische Universitaet Muenchen, Department of Informatics
D-85748 Garching, Germany
Tel: +49 89 289-17259     Fax: +49 89 289-17263

Time is money. Especially if you make clocks.




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