Re: [xml] Questions about xml:id

[Daniel Veillard <veillard redhat com>]

On Mon, Mar 21, 2005 at 09:48:39AM -0500, Bruce Miller wrote:
> Hi all;

  Hi,

 a set of good questions ...

>  libxml2 apparently supports xml:id
> [ http://www.w3.org/TR/2004/WD-xml-id-20040407/ ]
> but I'm a little unclear on how it works, particularly
> since I'm using libxml2 via XML::LibXML, rather than the C API.
>
> It seems that libxml2 only gives an attribute that magic ID-ness
> if the attribute's local-name is "xml:id"
>  [in perl:  $node->setAttribute('xml:id','someid'); ]
> rather than an "id" attribute in xml namespace
>  [in perl: 
>  $node->setAttributeNS('http://www.w3.org/XML/1998/namespace','id','someid'); ]
> Is this the intention?

  Well the focus so far has mostly been toward parsing xml:id and handling
it only from a serialization. I didn't really looked at it from an API
perspective. But the behaviour exposed sounds like a bug. 

> Second question: It appears that libxml2 creates an index of these ID's
> that is used by the xpath function id().  The index gets created

  right

> when a document gets parsed and/or validated.  Apparently, the index
> does not get `maintained' when a document is created or manipulated by hand.

  it's not complete probably. Removal of the attribute generate removal
from the ID table, but modification are not tracked down apparently.
Sounds like a bug too.

> Is there a `cheap' way to notice & update the association between ID & node
> when the structure gets rearranged?

  The functions used are xmlAddID() and xmlFreeID(), there is no mutation
callback associated.

> Alternatively a call (short of 
> validation)
> I can use when I _know_ the association has changed?

  yes, xmlGetID:

  http://xmlsoft.org/html/libxml-valid.html#xmlGetID

Daniel

-- 
Daniel Veillard      | Red Hat Desktop team http://redhat.com/
veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
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