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> Yes I think that is correct. With a correctly constructed
> formal semantics (i.e. assuming XQuery FS works :-),
> that is indeed what I expect would be a benefit, perhaps
> the major benefit.
My feeling is that unless the author of the query/transform has gone to
innordinate lengths to avoid it, any transform of real size is going to
use some generic function somewhere that forces the automatic typing of
the constructed transform to become more and more general. Individual
functions might end up being typed
"docbook author element" --> "xhtml span with @class=author"
but when you string everything together you'll end up with a function
from
document --> document
rather than anything specific.
> One of the reasons that I have become interested in such
> formalisms,
so am I actually (spent a lot of time programming in the strongly typed
standard ML language in a previous life) but while this might possibly
be made to work mapping from one XML view of a database table to another
XML view of a database table, where the XML is all well typed and under
control, I still think the chances of it working for an XSLT transform
that is taking arbitrary chunks of XML off the street and converting it
to something else are slim at best. All it takes is one
<xsl:element name="{substring(.,2,5)}"> (or its Xquery equivalent)
and you haven't a hope of figuring out any more specific type for
the result than "element" you can't tell what element it is never mind
if it is valid to use such an element at that point in any possible
result tree that might be constructed.
real transforms (rather than the 6 line examples in use case documents)
use libraries of thousands of templates, and checking that any library
you use never does anything like the above, just so you can typecheck
the transform is not something you can expect end users to do.
Since docbook->xhtml seems to be an example of choice, is
anyone really saying that given a docbook schema and an xhtml schema
that a system could typecheck Norm's docbook XSLT files and verify that
they always produce valid XHTML given valid docbook?
David
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