- From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
- Date: 19 Nov 2001 16:31:45 +0000
- To: Kevin Burges <xmldude@burieddreams.com>
- Cc: xmlschema-dev@w3.org
Kevin Burges <xmldude@burieddreams.com> writes: > >> <Check FormIDRef="FORM_2" FieldIDRef="FIELD_1"/> > >> > >> I need to check in this case that FIELD_1 exists within FORM_2. > >> > >> Are you saying I cannot do this at present? I thought that was the > >> point of having multiple <field xpath=""> elements? > > HST> The point of that is to identify something that has a multipart key. > HST> Your Field doesn't have it's own multipart key, it has a cascaded or > HST> multi-stage key -- first find Form with this key, then find Field with > HST> _this_ key. That's what's not supported yet, sorry. > > I *think* I understand what you're saying here but maybe not because > it still seems to me that I should be able to do what I want, at least > in part. > > I understand that a single key cannot assert the uniqueness of FormIDs > and FieldIDs within those, as that would be a multi-stage key. Lets > assume this uniqueness does not exist, and something like this was valid: > > <IDs> > <Form FormID="FORM_1"> > <Field FieldID="FIELD_1"/> > </Form> > <Form FormID="FORM_2"> > <Field FieldID="FIELD_1"/> > </Form> > <Form FormID="FORM_1"> <!-- NOTE: FORM_1 again --> > <Field FieldID="FIELD_2"/> > </Form> > </IDs> > > Could I not have a multipart key which consists of: > {@FormID @FieldID} > > which in this example would give: > {FORM_1 FIELD_1} > {FORM_2 FIELD_1} > {FORM_1 FIELD_2} Sorry not to be clearer. Yes, in principle, but no in practice, _for the Field element_. The decision to eliminate _inter alia_ '..' from the XPath expression subset for fields and selectors was made to put a reasonable bound on the cost of implementation to streaming processors. Note you _can_ do this if it's _Form_ elements which are uniquely keyed by the pair. ht -- Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh W3C Fellow 1999--2001, part-time member of W3C Team 2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440 Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk URL: http://www.ltg.ed.ac.uk/~ht/
Received on Monday, 19 November 2001 11:30:45 UTC