Re: [patch] removal of chiuldElement attributes in dispspec files

On Wed, 13 Oct 2004, David Malcolm wrote:

> On Wed, 2004-10-13 at 18:30 -0400, Douglas Burke wrote:
> > The attached patch changes occurrences of
> >
> >   <header-info childElement="foo"></header-info>
> >
> > to
> >
> >   <header-info xpath="normalize-space(child::foo)"/>
> >
> > in the dispspec file since the code does nothing with the childElement
> > attribute. I've also changed the DTD to remove the childElement attribute.
>
> Hmmm.... looks like the cong-dispspec-element-gxx.h was broken, and had
> the attribute "tag" rather than "childElement" for this, which was meant
> to initialise tagname; this failing would have caused failures in
> cong_dispspec_element_header_info_get_xpath_expression
>
> So this got me thinking: should we fix childElement, or get rid of it?
> Having two ways to do it felt overcomplex, so I decided to get rid of
> it.
>
> So I've applied your patch to the dispspecs directory, and hacked out
> the rest of the support from the dispspec loaders from the src
> directory.

Some thoughts I have about the use of an XPath expression to "personalise"
the title section of tags (i.e. the xpath element of the header-info tag
in an element):

1) How ofter should they be updated?

At present I don't think they are, which means you have to reload the file
if you add/change the item the Xpath expression points to. However,the
only safe way I can think of doing it would be to update all values after
any document change (or at least re-evaluate them all to see if the value
has changed). Which seems nasty.

2) Examples where I find the use of XPath limiting

For a document containing something like

  <examples><example>...</example><example>...</example></examples>

I have xpath="concat('Number of examples = ',count(example))" for the
examples tag. I would like each example tag to have an XPath expression
which results in the text "Example <n> of <m>". It's easy to get the <m>,
but not the <n>, via XPath. Or perhaps I should say I can't work out how
to get the <n>.

Another case is that of conditionals; e.g. if there is a child element
called title then use its contents, but if not then act as if there is no
XPath expression.

3) does it make sense to make the EXSLT functions in libxslt2 available
for use in the xpath expressions?

Doug