[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Public Identifiers
Regarding FPIs (formal public identifiers) and their role (or lack thereof) in Web applications: (Note: in the following, I use the term "namespace" in its generic technical sense, without reference to XML "Namespaces". As far as I know, this note has nothing to do with XML "Namespaces".) Will URNs permit pointing to things that aren't now and may never be on the web? I mean, things that their owners never intended to be on the web and either that their owners do not want to appear on the web, or that their owners may not (currently) see any interest in putting on the web? I ask this partly because one of the interesting things in the forthcoming Topic Navigation Map standard is the use of FPIs to point at so-called "public topics" -- topics that are identifiable by a name in some namespace maintained by any arbitrary authority. All you need is an unambiguous way to point to the authority, the namespace maintained (or the namespace that was once created) by the authority, and the name in that namespace. For example, to consider a certain obsolete farm implement as a topic: Authority: Sears, Roebuck & Co. Namespace: 1922 Farm Catalog Number Name: R205 According to the current Topic Navigation Map draft (soon to be CD 13250), this would appear as the following FPI: -//Sears, Roebuck & Co.//NONSGML TOPIC 1922 Farm Catalog Number : R205//EN Can URNs do that? I sure wouldn't want XML to be unable to do this kind of thing. If it couldn't, that would rule out the use of public topics in XML-based topic maps. Public topics are very useful for correlating the knowledge contained in disparate topic maps, so the concept of "public topics" seems pretty important to me. You may ask, "What does non-web information have to do with the Web?" Good question. Personally, I think it has plenty to do with it, but I suspect others might disagree with me. I would venture to say that, even today, a significant fraction of all FPIs are not intended to be resolved, but rather simply to sit there and be pointers, documenting the sources of authoritative material that bears on the actual online content, but to which direct access is not needed in order for applications to run. One example is the FPIs of Architecture Definition Documents in Base Architecture Declarations. [To HyTime aficionados, using other words, I would say that one of the most important applications of FPIs is in lieu of biblocs. (A HyTime "bibloc" is a pointer to an offline resource; this facility allows pointing to things that belong to authorities that have not endowed them with online addresses of any kind.)] I'm not just being provocative here; I'm really interested to hear what the readers of this list have to say about this. Part of the issue is whether and how to honor the reality that people and institutions may be regarded as authorities and keepers of online-significant namespaces, whether or not they want to be so regarded, and whether or not their namespaces actually exist online. The existence of FPIs that identify namespaces that are not online could, in sufficient numbers, and in applications of sufficient economic importance, actually have the effect of bringing such namespaces online. If we take that view that the purpose of W3C standards is to enhance human productivity by increasing the availability of knowledge, then it's clearly desirable to have this kind of bellwether indicator of business opportunity. It seems to me that we should consider the ability to reference names in offline namespaces a requirement for XML, and so I'm glad that public identifiers exist in XML. Please let's not deprecate FPIs; instead, let's understand and celebrate the difference between FPIs and URNs, even if/when URNs are terrifically indirect. For me, the essential difference between URIs and FPIs has nothing to do with any particular scheme of indirect addressing, cataloging, or algorithm for resolution. On the contrary, FPIs remain essential to XML precisely because URIs, including URNs, are really system addresses, where the system is the Web, if we consider the Web as including some array of standardized URI resolution facilities. FPIs are different from URIs precisely because, for FPIs, no machine-executable resolution algorithm is standardized, specified, or even necessarily understood, and it's useful and vital to be able to reference things in such a fashion. -Steve -- Steven R. 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