Re: Base URLs

David Robinson (
Thu, 9 Feb 95 19:31 GMT

Message-Id: <>
Date: Thu, 9 Feb 95 19:31 GMT
Subject: Re:  Base URLs
From: (David Robinson)

>In draft-ietf-uri-relative-url-05.txt, "within Document Content" (3.1)
>overrides "within Message Headers" (3.2). Is there a reason for this order? I
>can think of reasons for putting these two the other way round, but not for
>this order.

To my mind, a base URL defined within Message Headers is a base URL for
other URLs within the _headers_. For documents which cannot or do not
contain a base URL, then it is reasonable for the document to inherit
any base URL defined in message headers. However, the semantics of the
document should not be changed simply by ecapsulating it in the headers
of a transport protocol. Especially as the document will usually be opaque
to the transport system.

A specific example: WWW-Authenticate: response headers. The current HTTP spec
defines the base URL for these headers to be the URL of the requested
resource. I would prefer the server to be able to choose the base URL with
a Base: header without always altering the base URL for the document.

So, in fact, I would prefer a completely different interpretation than given
in 3.1/3.2:

1. The base URL is found from the document content. for an HTML document,
   it is as given in Appendix 10.  For documents which are RFC 822 style
   messages, the base URL is as given by the Base: header.

2. Otherwise, the base URL of the document is the base URL of the document
   which encloses this document.

3. Otherwise the base URL of a document (not enclosed in any other) is defined
   by the context in which it is retrieved; i.e. its URL.

Reading the relative URL draft further, I find that it gives this
interpretation in 3.3 para 2 (but to MIME documents). Why distinguish message
headers from other retrieval contexts?

 David Robinson. (