- From: Graham Klyne <GK@acm.org>
- Date: Thu, 10 Jul 1997 16:29:27 +0100
- To: Koen Holtman <koen@win.tue.nl>
- Cc: http-wg@cuckoo.hpl.hp.com
Koen, A couple of comments regarding your feature registration draft... * Section 3.6, item (3): In conflict with section 2.2 final paragraph, this item does seem to place prior restrictions on the things can be identified by a feature tag. Specifically, the wording suggests the range of a feature value must be a scalar type (enumeration, number range, etc.). Compound values seem to be excluded; e.g. sets (multiple choices), cartesian products (multidimensional values). Consider an example of a (hypothetical) map server: one might wish to request a map covering a specified rectangular(-ish) area (4 real numeric values) OR including all of a designated set of counties, with a specified mapping resolution and containing a minimum specific set of mapping features. [As an aside: it occurs to me that, in HTTP transfers, the resource identifier (URN, URL or whatever) might be considered just another dimension of the negotiation!] * Section 3.8: (A) In "Summary of the indicated dimension of negotiation", I am uncomfortable with your use of the term 'dimension' in this context. I think what you are describing is the range of values associated with a dimension. Underlying this comment is my feeling that I don't think sufficient distinction is drawn between identification of a dimension of negotiation (the feature tag) and the values which are associated with that dimension (feature values?). (B) I feel your list of "Result in the indicated dimension of negotiation" is rather arbitrary. Why separate items (1) and (2)? Similarly (3) and (4) in that they both represent a choice from an enumeration of values. I would suggest: (1) A yes/no choice (2) A choice of one value from a finite enumeration of (possibly numeric) values (3) A choice of multiple values from a finite enumeration of values (powerset) (4) A value selected from a finite or infinite range of some scalar type (integer, real) (5) A compound value (e.g. MIME Content-type, range of numeric values) [I also note that these values relate to a specific message which is transferred: the feature negotiation mechanism would have to deal with multiple values for any of these value range types.] GK. --- ------------ Graham Klyne GK@ACM.ORG
Received on Thursday, 10 July 1997 08:34:19 UTC