Setting global variables [SEC=UNCLASSIFIED]

[Nicholas.Ardlie at ga.gov.au]

I'd be interested to hear opinions on this too.
I found the need for a similar solution and have ended up using both:

(1) A file of static input variables (passed to each XQuery via a Java
wrapper) 
and
(2) An XMLDB collection loaded with instances of various content models or
schemas. These models effectively dictate functional behaviour. E.g. in your
example the "mydoc.xml" containing names data would be pre-loaded and
accessed by a resolver function in an XQuery module. Which gets called by
various local XQuery functions.

Regards,
Nick.


-----Original Message-----
From: http://x-query.com/mailman/listinfo/talk [mailto:http://x-query.com/mailman/listinfo/talk] On Behalf Of
Ronald Bourret
Sent: Wednesday, 31 October 2007 4:55 PM
To: xquery-talk
Subject:  Setting global variables

Is there any way to set a global variable from inside a function? (By 
"global variable", I mean a variable declared in the prolog of a 
function library.)

Basically, I'd like to read a document and save a subset of the document 
in a global variable, then refer to it later when doing lookups. For 
example, I'd like to do something like the following:

    declare variable $foo:listOfNames external;

    declare function foo:firstFunctionCalled(...)
    {
       let $foo:listOfNames := fn:doc("mydoc.xml")//Name
       ...
    };

    declare function foo:functionCalledMuchLater(...)
    {
       ...
       if ($name = $foo:listOfNames)
       ...
    };

Currently, I pass such information from function to function until it is 
finally used. While this works (and some would argue is the correct 
style), it has the following drawbacks:

1) It is difficult to follow the information through the chain of functions.

2) It can be confusing to read the intermediate functions, as these 
never really use the information.

3) It is brittle when refactoring the intermediate functions. Because 
the information is not really used -- it's just passed along -- it is 
easy to accidentally drop.

Thanks,

-- Ron

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