RE: [xsl] Normalize / Simplify HTML-Tables with row-span / col-span

["Michael Kay" <mhk@xxxxxxxxx>]

>  Is it not possible for the processor to initially use RTFs 
> and then convert to a node-set internally when needed?  
> Excuse my naivety here, but it seems the obvious solution.

It's certainly possible to use a variety of "lazy evaluation" strategies
to ensure that the cost of building a tree is only incurred
incrementally depending on the facilities that you actually use. It's
also possible to use static analysis of the stylesheet to work out what
capabilities are needed in advance. Saxon uses a little bit of both of
these techniques, but there is scope for a lot more. For example, Saxon
statically recognizes many of the cases where the tree will contain only
a single text node, and uses a special data structure for that case. If
I hadn't been so busy implementing new functionality for the last two
years, then it would do a lot more of this kind of optimization by now!

Certainly, I don't think there is any justification for imposing
restrictions on the user-visible language in order to make
implementations faster in this area. It's very rarely good design to do
that.

Michael Kay


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