[Monetdb-developers] XRPC syntax

Jens Teubner jens.teubner at in.tum.de
Fri Oct 27 12:38:01 CEST 2006

On Tue, Oct 24, 2006 at 03:40:16PM +0200, Ying Zhang wrote:

> Our intention is to allow an XQuery expression here (after "at"), but it
> should be evaluated to a URILiteral.  How can I correct this rule to
> express our intention?

This is a typing thing, and I've already implemented that.  Whatever the
expression after "at" evaluates to, we try to cast it into a string.
This is in line with how XQuery is defined elsewhere.

You cannot express such a restriction in your grammar, though.  This is
a pure typing thing.

> With or without '{' and '}' doesn't matter for me:)  So, if the braces
> make it easier for parsing, we should then just adjust the syntax
> definition.

Done already. :-)

> I'd like to mention that we need to check that the called function
> belongs to an imported module, thus it should not be a built-in function
> or a UDF which is in-line with the query.

I will have to think about how we can implement such a check most
elegantly within Pathfinder.  I'm wondering about its usefulness,
though.  I accept that we may want to restrict it to non-built-ins only.
But is the import via a module a sensible restriction?  I could easily
create some module with some function definition and import it.  Still,
the respective function would not be available at the XRPC target
machine.  I think we cannot really check whether a target machine will
actually implement a given function (and if it does so with the same
argument types).  So we will have a garbage in, garbage out situation
always.  Does it then make sense to do this very special check at all?


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

SQL0437W  Performance of this complex query may be sub-optimal.
Reason code: "3".  SQLSTATE=01602
                         -- IBM DB2 V7.1 Warning Message

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