[DAS2] Why use URIs for feature IDs?
Gregg_Helt at affymetrix.com
Thu Feb 9 16:40:34 UTC 2006
Interesting, I hadn't fully absorbed part 4 of the URI spec (rfc2396).
So if I understand correctly:
If we replace everywhere we've called something a "URI" with "URI
reference" we're being correct -- a URI reference can be an absolute or
relative URI, and can also include a fragment identifier. And according
to the spec saying "the URI" means the absolute URI, not the relative
URI. So to restate, I think the ids we use in DAS/2 should be URI
references. Maybe instead of "id" or "uri" we should use "uri_ref" for
the attribute name?
I still see no reason to exclude URI references with fragment
identifiers, though I agree with Lincoln that actually resolving a URL
with a fragment is problematic. But we're not guaranteeing that these
URI references are URLs anyway.
The capabilities "query_id" attributes are another story. These need to
be not just URI references but also resolve via XML-Base to full URLs.
> From: das2-bounces at portal.open-bio.org
[mailto:das2-bounces at portal.open-
> bio.org] On Behalf Of Andrew Dalke
> Sent: Thursday, February 09, 2006 7:43 AM
> To: DAS/2
> Subject: Re: [DAS2] Why use URIs for feature IDs?
> > As I understand it a fragment identifier approach would mean
> > URI = (URL of doc feature XML is embedded in) + "#" + value of
> > feature's
> > ID attribute.
> As I understand it the part after the '#' is a query language
> which is document type specific and used by the client. DAS does not
> define how that query language is used, so it has no meaning in the
> DAS world.
> 4. URI References
> The term "URI-reference" is used here to denote the common usage
> resource identifier. A URI reference may be absolute or relative,
> and may have additional information attached in the form of a
> fragment identifier. However, "the URI" that results from such a
> reference includes only the absolute URI after the fragment
> identifier (if any) is removed and after any relative URI is
> to its absolute form. Although it is possible to limit the
> discussion of URI syntax and semantics to that of the absolute
> result, most usage of URI is within general URI references, and it
> impossible to obtain the URI from such a reference without also
> parsing the fragment and resolving the relative form.
> 4.1. Fragment Identifier
> When a URI reference is used to perform a retrieval action on the
> identified resource, the optional fragment identifier, separated
> the URI by a crosshatch ("#") character, consists of additional
> reference information to be interpreted by the user agent after
> retrieval action has been successfully completed. As such, it is
> part of a URI, but is often used in conjunction with a URI.
> fragment = *uric
> The semantics of a fragment identifier is a property of the data
> resulting from a retrieval action, regardless of the type of URI
> in the reference. Therefore, the format and interpretation of
> fragment identifiers is dependent on the media type [RFC2046] of
> retrieval result. The character restrictions described in Section
> for URI also apply to the fragment in a URI-reference. Individual
> media types may define additional restrictions or structure within
> the fragment for specifying different types of "partial views"
> can be identified within that media type.
> A fragment identifier is only meaningful when a URI reference is
> intended for retrieval and the result of that retrieval is a
> for which the identified fragment is consistently defined.
> dalke at dalkescientific.com
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