RE : [Moderator Action] Rules for evaluation context

Sent to www-forms-editor

> -----Message d'origine-----
> De : www-forms-editor-request@w3.org 
> [mailto:www-forms-editor-request@w3.org] De la part de Michael N. Lipp
> Envoyé : dimanche 9 février 2003 22:08
> À : www-forms-editor@w3.org
> Objet : [Moderator Action] Rules for evaluation context
> 
> 
> 
> 
> 
> Hi,
> 
> Trying to implement the calculation of the evaluation context 
> (7.3 from the spec). I have run into the following problem: 
> let's assume I have a model with id="M1" (and the sample 
> instance from 7.3 of the
> spec) and another model with id="M2" (with instance data 
> <root xyz="5"/>). Now how do I resolve this:
> 
> <group ref="level2/level3" model="M1">
>     <select1 ref="/root/@xyz" model="M2"/>
> </group>
> 
> I would expect the reference for select1 to be resolved to 
> "5". But if I apply the rules from 7.3, I find the following:
> 
> (1) <select1 ref="/root/@xyz" model="M2"/> is not an outermost binding
> 
> (2) So rule 2. from 7.3 applies: "The context node for 
> non-outermost binding elements is the first node of the 
> binding expression of the immediately enclosing element."
> 
> (3) So, my context node is "level3" from model "M1".
> 
> (4) Applying the xpath expression "/root/@xyz" to this 
> results (at best) in something empty.
> 
> (5) Have I forgotten to apply rule 3. from 7.3? Maybe. "The 
> context node [even of my non-outermost binding element] 
> resides within the context model, which is determined 
> choosing the first item that applies from this list: a. if a 
> model attribute is present on the binding element, the 
> attribute determines the context model...". OK but how does 
> it help? It is obviously not true for the result returned in 
> (3). Is the above example illegal?
> 
> (6) Does rule 3. from 7.3 have a kind of precedence? I.e. 
> should I evaluate "level2/level3" using model "M2"? This 
> contradicts rule 2. from 7.3 because is states that "The 
> context node for non-outermost binding elements is the first 
> node of the binding expression of the immediately enclosing 
> element.". The "binding expression" of the group element, 
> however, is obviously "level3" from model "M1".
> 
> (7) Should I assume that a rule is missing: "A non-relative 
> path in "ref" binds the context node to the first node 
> returned from applying the path to the instance data of the 
> context model". I wouldn't like this. First, it is not easy 
> to be sure that a path is non-relative: 
> "node1/node2/instance('I2')/root" is (though silly) absolute 
> but it does not look like it. Second, I would expect 
> "<select1 ref="@xyz" model="M2"/> to return "5" in the 
> example above as well (though I'd also accept this to be 
> defined as an illegal selection -- note, however, that it is 
> not illegal based on the current rules).
> 
> (8) Should I assume that the "immediately enclosing element" 
> should be defined like this: "An element is 'immediately 
> enclosing' when it is the first binding element node THAT HAS 
> THE SAME CONTEXT MODEL AS THE NON-OUTERMOST BINDING ELEMENT 
> in the node-set returned by the XPath expression 
> ancestor::*.". I'd prefer this, because it is easy to 
> implement ;-) and I think matches intuitive expectations.
> 
> (9) Have I totally misunderstood something?
> 
>    - Michael
>

Received on Monday, 10 February 2003 04:55:49 UTC