Re: [xml-dev] Best Practice: id-idref or external entities?

[daniela florescu <dflorescu@mac.com>]

Entities, I have no opinions about. They get resolved before the XML Data Model (XDM) comes into the
picture for XQuery/XSLT processing.

The problem is with id/idrefs and their combination with XQuery/XSLT/Xpath set of specifications.

Examples:
1. nodes in XDM have an abstract unique identifier
2. this should NOT be confused with the @id attribute
3. the abstract identifier is unique across a universe that is NOT defined by the XDM, while the @id is unique on a document level
4. the abstract identifier is not serializable by default (it might in some implementations), while the @id obviously is
5. it is not clear to me how the @id/@idref non dangling pointers, aka @idrefs pointing nowwhere,
 is maintained through XQuery Updates (if at all) in case of general XML databases which do not consider “documents” a first class citizen.

Etc, etc, etc.

Id/idrefs and XDMs have been orthogonal in their design since the beginning, and it is better not to tempt the devil 
in this fragile area. 

It might become a source of nasty bugs, depending on the implementation.

Hope that helps,
Dana





> On Oct 8, 2015, at 7:34 AM, David Carlisle <d.p.carlisle@gmail.com> wrote:
> 
> On 8 October 2015 at 13:10, Daniela Florescu <dflorescu@mac.com> wrote:
>> My personal point of view would be very simple to express: avoid them if you can.
>> 
>> They mix very badly with XQuery and co.
>> 
>> Best regards
>> Dana
> 
> I'm not sure if you mean avoid entities here, or avoid id references?
> 
> Both have good and bad aspects with respect to XQuery/XSLT processing
> it seems to me.
> 
> We use entities (internal rather than external mostly, but that's not
> really relevant here) a lot precisely because they are transparent to
> the XSLT/Xquery processing.
> 
> To follow id/idrefs (or xlink or any custom link like xhtml href)
> requires more code at the XSLT level, although they typically help
> manage other properties such as uniqueness, so as usual, the answer
> depends on what you want to do....:-)
> 
> David