Global tags [was: HTTP Protocol Extentions]

Arthur van Hoff wrote:
> I would prefer an approach where a global entity tag is
> not opaque. For example:
> 
>    entity-tag = [ weak ] opaque-tag | global global-tag
>    weak       = "W/"
>    opaque-tag = quoted-string
>    global     = "G/"
>    global-tag = <"> URI *( "," URI ) <">

This is ambiguios. "," can occur in a URI, so it's not clear
whether:
	G/"foo:bar,baz:blort"
parses as URI "," URI or just one URI with a "," inside it.

I suggest in stead:
	global-tag = <"> URI *(" " URI) <">
since " " cannot occur (unescaped) in URI.

>    md5-URN    = "urn:md5:" base64-number
>    sha-URN    = "urn:sha:" base64-number

I suggest that the characters "urn:" don't add anything
but a dependency on an in-progress spec. I suggest in stead:

    md5-URI    = "md5:" base64-number
    sha-URI    = "sha:" base64-number

And, by the way, the definition of md5-URI and sha-URI don't
belong in the HTTP spec, but in separate drafts just like
all the other URI schemes.

> This would assign some structure to the global tag name
> space, which means that collissions can be avoided,
> and it would allow a client to parse the URIs and verify
> checksums when necessary.

Yup.

More on diff-range-specifier separately.

-- 
Dan
http://www.w3.org/People/Connolly/