Re: URL semantics
Daniel LaLiberte <liberte@ncsa.uiuc.edu> Fri, 10 January 1997 19:55 UTC
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From: Daniel LaLiberte <liberte@ncsa.uiuc.edu>
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Date: Fri, 10 Jan 1997 12:44:08 -0600
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To: Tim Berners-Lee <timbl@w3.org>
Cc: uri@bunyip.com
Subject: Re: URL semantics
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> At 11:27 am 09-01-97 -0600, Daniel LaLiberte wrote: [I wrote this, in case anyone missed it] > >But for all URLs (and URNs, if they may be distinguished), the URL > >identifies the interaction. In the case of *some* URLs, the > >interaction results in a data object, so it only *seems* that the URL > >identifies the data object, but that is an indirect effect. Tim Berners-Lee writes: > I completely disagree. The URL identifies the object. That is > fundamental to the concept of the web. The web is a web of > quasi static resources, not a set of operations, as base. This > is essential architecturally and from the UI point of view. OK, I think it works both ways. But if you say a mailto URL identifies an object, and that object is a conceptual entity upon which you can do many operations (such as send a message to the address, or lookup previous sent or received messages associated with the address), and there is no particular one place that the conceptual object resides, or one service that you interact with, then we essentially have a collection of possible operations (and associated data) packaged up as an "object". In fact, one way of defining an object is as a set of allowed operations on the object. To the client of an object, the object is *nothing but* the allowed operations on it. So I should have been a bit more specific and said the URL identifies (by way of an abstract object) a set of *possible* interactions. And the possibilities are, as you say, controlled by the user (and any server that must cooperate). > If you wanted to make something which contains an interaction, some > operation, then you would need a language in which resource identifiers > were a part. But there are many languages for that, and there can be many > more. (A frameset is one, a form is another, Java is another.) A complex language is not needed in order to express operations. An http URL essentially expresses that the client should lookup the domain name, send an HTTP request to the server, etc. Alternatively, a client could interpret the same URL differently and lookup the URL in a set of caches, or lookup the URL in a content rating service. The language of http URLs is very declarative. In general, any identifier is an expression in that the user of the identifier interprets it. If the identifier is completely opaque, then there is nothing to interpret. But all the URI schemes define visible structure down to a certain level of granularity. The visible part lets the client partially interpret it to pull out the components. The remaining opaque parts and components are interpreted by other services (e.g. dns and http servers). > PS: Above I use "object" to be consistent with the thread, I should > use "resource". I'm fine with "object", but analogously, "GET" could mean "do the intended interaction". But people have a habit of jumping to conclusions. dan
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- Re: URL semantics Daniel LaLiberte
- Re: URL semantics Gregory J. Woodhouse
- Re: URL semantics Tim Berners-Lee
- Re: URL semantics Daniel LaLiberte
- Re: URL semantics Tim Berners-Lee
- Re: URL semantics Larry Masinter
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