Re: [xsl] String conversion problem when string is large

[Michael Kay <mike@xxxxxxxxxxxx>]

> Just to confirm, do I read correctly that
>
> <xsl:param name="string" as="xs:string">string</xsl:param>
>
> will be passed and processed as a string rather than a tree?
Yes, that's correct. Technically a document is constructed and then 
atomized to create the string, but it doesn't require a great deal of 
brain-power to short-circuit this.

Actually with Saxon this will also often happen with:

<xsl:param name="s">string</xsl:param>

With xsl:param and xsl:variable Saxon attempts to analyze the usage of 
the variable. If all uses of the variable are in atomizing contexts, 
then Saxon rewrites it as a string to avoid the overhead of creating the 
tree. But there's no attempt to do this in the case of xsl:with-param, 
because it requires global analysis, prevention of cycles when handling 
recursion, etc.
> I have been working in the belief (also in analogous cases) that it 
> does, but as long as we're on the topic I wonder if you can speak to it.
>
> Plus, I am wondering whether I can know that this will happen in any 
> XSLT 2.0 processor, not only Saxon.
Since most XSLT 2.0 processors are closed source, we have no way of knowing.
> The main reason I need this settled in my mind is that, as you say, 
> this comes up very commonly; and one of the most mystifying pieces of 
> advice we give to beginners is to prefer using @select, when possible, 
> to a literal value in a parameter or variable assignment, even though 
> the latter is legal and it works, under one definition of "work". If 
> the workaround is really this easy (and if it even suggests the nature 
> of the underlying problem, as this appears to), that might help.
>
> In other words, if
>
> <xsl:param name="string" as="xs:string">string</xsl:param>
>
> is long for
>
> <xsl:param name="string" select="'string'"/>
Well, there are other benefits in declaring the type. These two 
constructs aren't equivalent, because in the first case the processor 
knows that the value will always be a string, whereas in the second it's 
only a string in the case where it's defaulted.
> we should see similarly that
>
> <xsl:param name="string">string</xsl:param>
>
> is another way of saying
>
> <xsl:param name="string" as="document-node()">
> <xsl:document>string</xsl:document>
> </xsl:param>
>
> Is this correct?
Yes, that's true.

Michael Kay
Saxonica