Re: Extension candidates

On Thu, Dec 11, 2008 at 12:06 PM, Michael Kay <[email protected]> wrote:
>>   Michael and Dimitre have just added new extension
>> candidates on http://www.fgeorges.org/exslt2-wiki/.  Thank
>> you!  I have a few questions about them...
>
> I wonder if we shouldn't capture the discussion on the wiki itself. Start by
> creating a page for discussing each candidate extension, then put the
> questions there and let each evolve into a specification.

Completely agree. Thus it will be available and everybody could join
the discussion.

>>
>> > * xx:node-ref() - for any node produce a value, which can be
>> >   used to obtain this node (node reference)
>>
>> > * xx:node-from-ref() - navigate to (select) a node from its node
>> >   reference
>>
>>   By "value," do you mean "atomic value"?  I am not sure to
>> see exactly the purpose, would you have a sample use case?
>
> There's been a fair bit of discussion of such functions on the XQuery WG
> mailing list in the last few weeks.
> Some people wanted the ref to take a
> form of a string or URI so it could be stored in a document. Some wanted
> ref() to be synonmous with generate-id(). Some wanted it to be a ref() to
> any value (sequence), not necessarily just a node. A big difficulty is the
> interaction with garbage collection. There are two conflicting requirements
> - the reference should be a string, so you can store it in a document; but
> the node should continue to exist so long as the reference exists. Basically
> these two requirements come from different use cases, and I think they might
> need different facilities.

These two requirements are not conflicting. I imagine an
implementation where references are stored in a hash table, where the
string is the key and the actual reference is the value.

-- 
Cheers,
Dimitre