RE: XSL variable types

[Kay Michael <Michael.Kay@xxxxxxx>]

> From: Jon Smirl [mailto:jonsmirl@xxxxxxxxxxxx]
> Sent: 12 August 1999 18:54
> To: XSLList
> 
> The XSL spec talks about five data types:
>     string, number, boolean, node-set, result-tree
> 
> XT allows me to set variables to Java objects (ObjectVariant) 
> and I'd like to modify Saxon to support this as well.  Should there be a 
> documented sixth data type of 'opaque' which is only used for passing
things between
> extension functions? It would be defined as error if used in 
> any other way.
> 

Actually XPath specifies four explicit data types (string, number, boolean,
node-set) and allows "other", while XSLT provides result-tree as an example
of "other". This leads to some interesting complications, e.g. the semantics
of comparing a node-set to a result-tree are undefined.

I'll have a look at allowing general objects as parameters to SAXON
extension functions. Really I'd prefer it (and I'm sure users would!) if the
standard defined a Java interface to extension functions. I'm not totally
happy with xt's introspective approach, for example it doesn't leave room
for requiring an extension function to declare whether or not it has
side-effects.

Mike Kay 


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