tclxml-users

[Tclxml-users] XPath usage in tcldom

[Derek F. <fo...@hu...>]

I notice from recent posts to this list that tcldom has some xpath support - 
selectNode and createNode. I've started to rely on these as they make my 
scripts much easier to write, and I'm at the point of ripping out all my DOM 
walking code and replacing it with selectNode calls.

Before I do this I ought to check: since these calls are non standard, what 
is the prospect for their future? Will they get replaced with something else, 
or can I assume they'll be available on all forthcoming tclxml versions for 
the foreseeable future?

-- 
The past: Smart users in front of dumb terminals

Re: [Tclxml-users] XPath usage in tcldom

[Joe E. <jen...@fl...>]

Derek Fountain wrote:

> I notice from recent posts to this list that tcldom has some xpath support -
> selectNode and createNode. I've started to rely on these as they make my
> scripts much easier to write, and I'm at the point of ripping out all my DOM
> walking code and replacing it with selectNode calls.
>
> Before I do this I ought to check: since these calls are non standard, what
> is the prospect for their future? Will they get replaced with something else,
> or can I assume they'll be available on all forthcoming tclxml versions for
> the foreseeable future?

The Expat-based implementation (in tcldom/src, formerly known
as TclDOM-Pro) doesn't include XPath support, and probably
never will unless someone else takes the trouble to implement it.
I don't plan to -- IMO implementing XPath is more trouble than
it's worth.

(Personally, I use a homegrown XML query language built on top
of TclDOM; it has most of the power of XPath, but was significantly
easier to implement).


--Joe English

  jen...@fl...

Re: [Tclxml-users] XPath usage in tcldom

[Steve B. <Ste...@zv...>]

Joe English wrote:
> The Expat-based implementation (in tcldom/src, formerly known
> as TclDOM-Pro) doesn't include XPath support, and probably
> never will unless someone else takes the trouble to implement it.
> I don't plan to -- IMO implementing XPath is more trouble than
> it's worth.

I wonder whether the Tcl implementation's XPath code is
generalised enough to be used with a TclDOMPro DOM tree?
I'd have to check to see if it only uses API calls,
rather than peeking directly inside the node data structures.
I'm pretty sure the createNode stuff falls into that category.

This approach may apply to other features, such as events.

> (Personally, I use a homegrown XML query language built on top
> of TclDOM; it has most of the power of XPath, but was significantly
> easier to implement).

Horses for courses...

Having invested the time in learning XPath, I like to
leverage that investment.  XPath is popping up all over the
place - XSLT, XML-Query, DOM, etc.  I've no doubt that
it may be easier to design/implement other query languages
(especially now that I've read the XPath v2.0 WD - phew!)
but sticking to standards (as much as possible) is important to me.

Cheers,
Steve Ball

-- 
Steve Ball            |   XSLT Standard Library   | Training & Seminars
Zveno Pty Ltd         |     Web Tcl Complete      |   XML XSL Schemas
http://www.zveno.com/ |      TclXML TclDOM        | Tcl, Web Development
Ste...@zv...  +---------------------------+---------------------
Ph. +61 2 6242 4099   |   Mobile (0413) 594 462   | Fax +61 2 6242 4099

Re: [Tclxml-users] XPath usage in tcldom

[Steve B. <Ste...@zv...>]

Derek Fountain wrote:
> I notice from recent posts to this list that tcldom has some xpath support - 
> selectNode and createNode. I've started to rely on these as they make my 
> scripts much easier to write, and I'm at the point of ripping out all my DOM 
> walking code and replacing it with selectNode calls.
> 
> Before I do this I ought to check: since these calls are non standard, what 
> is the prospect for their future? Will they get replaced with something else, 
> or can I assume they'll be available on all forthcoming tclxml versions for 
> the foreseeable future?

Well, I rely on XPath too so I'm pretty keen on making
sure it continues to be supported.

DOM Level 3 includes interfaces for XPath, so the standard
itself will support XPath.  Of course, bridging the gap
between DOM and XPath's data models is not trivial so it's
not all smooth sailing.

As with all non-standard extensions, the syntax introduced
in DOM Level 3 may not (will not) match the selectNode/createNode
methods (btw, at least L3 has the notion of static node lists
so we don't have to worry about live lists).  The usual
response to that is to keep the original syntax, deprecate it
but maintain the extension syntax for the forseeable future.

HTHs,
Steve Ball

-- 
Steve Ball            |   XSLT Standard Library   | Training & Seminars
Zveno Pty Ltd         |     Web Tcl Complete      |   XML XSL Schemas
http://www.zveno.com/ |      TclXML TclDOM        | Tcl, Web Development
Ste...@zv...  +---------------------------+---------------------
Ph. +61 2 6242 4099   |   Mobile (0413) 594 462   | Fax +61 2 6242 4099