Re: [xml-dev] MicroXPath proposal

[John Cowan <johnwcowan@gmail.com>]

On Thu, Jan 13, 2011 at 10:01 PM, Liam R E Quin <liam@w3.org> wrote:

> At any rate,
> the ability to return non-nodes was a much-asked-for thing; the general
> trend seemed to be to want the language to be simpler, in having fewer
> odd quirks, and more flexible. The type system and a few other added
> features ended up making it noticeably larger, but there's good in there
> too...

I got curious just how much larger.  On my system, the XPath 1.0
document, which also documents the data model and the available
functions, is 37 pages.  XPath 2.0 + XDM + F & O is 367 pages.  That's
an order of magnitude larger, rather than just "noticeably" so.

Again, I doubt if I can write down a coherent XPath subset in 3.7
pages, but it would be interesting to try.

On Fri, Jan 14, 2011 at 9:58 PM, James Clark <jjc@jclark.com> wrote:

> The only subset of XPath 1.0 that makes sense to me is one that has the goal
> of being able to create one path that uniquely identifies any element (and
> perhaps attribute) in a document. Something like
>   /foo[2]/bar[1]/baz[3]

Well, that's something worth having for sure, and even treating
specially, because it can be made to return a single Element rather
than an iterator.

On Sat, Jan 15, 2011 at 10:04 PM, Uche Ogbuji <uche@ogbuji.net> wrote:

> I agree with the above until the last point.  I also believe that the
> "streamable" subset of XPath 1.0 is useful, though of course people
> establish such a subset in several ways.  I'd say XSLT 1.0's pattern
> language comes close enough for most uses.

Now that's a *very* interesting idea: the path would allow / and //,
and the legal path steps are: name, *, @name, @*, text(), and
id(name).   That's very close to my original proposal.  But patterns
are no simpler than XPath 1.0 for the implementor, because *any*
expression can be a predicate in a pattern, so you end up having to
implement the whole of 1.0 anyway.  What is the simplest set of
predicates that could possibly work?

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