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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: simple question on namespaces.
 On Thu, 28 Dec 2000, Tim Bray wrote: > I think a helpful question is "What can you do with little chunks > of XML when they *don't* have names unique across the Net?" The > answer is "Not much." What can you do with little chunks of XML when they don't have meaning *shared* across the Net? Not much, again. > Hence, namespaces, and if all they ever did was provide names, > that'd be fine. Only to those who already know what those names mean. In a public environment like the Net, where the point is to agree on and share definitions, a "controlled vocabulary" without a means to verify formal validity is magnificently useless. Another "blast from the past" (also indirectly addressing PaulT's fears about a Tool X being inevitable): :> I do not expect that a namespaces NSDef can be dereferenced to :> obtain a schema. [...] The immediate use I see namespaces put to :> is recognition: Programs can test names to see whether they :> match a specific namespace and local name, thereby distinguishing :> names that would be otherwise conflictingly ambiguous. For :> example, a processor looking for a MathML DIV element could :> recognize it, and distinguish it from an HTML DIV element, :> without reading any schemas at all : : But how does a processor know that "DIV" is a valid name within the : MathML name space unless there is an authoritative definition of : what the vocabulary of type names is within MathML? [...] you can't : claim that a name space is controlled unless there is a defined and : standardized way to define the vocabulary and the name space : proposal does not define one (even though XML does: DTDs). : : Either the NS URI must *always* points a formal definition of the : vocabulary (not schema) of the name space so that you (and your : processors) can reliably examine that definition to validate that : names you've encountered are really in the vocabulary or you can : never know for sure that a given name is "supposed" to be in a name : space because even if there is a resource at the end of the URI, : there's no standardized definition of what you might get, so can't : trust that you'll ever get anything useful, if you get anything at : all. : : You might know that, yes, "DIV" is defined by MathML because you : happened to have lunch with the MathML team and they told you that, : but you don't know that "Farglebarp" *isn't* in the MathML : vocabulary and therefore, should you encounter MathML:Farblebarp, : you won't know if you're at fault for not knowing about the : Farglebarp tag or if the document author is at fault for misspelling : ForgleBurp as Farglebarp. In addition, without an authoritative : definition of the vocabulary, you can't prove to anyone else that : your support for the DIV element is in fact appropriate because you : have no authority to point them to to prove that DIV is in the : MathML vocabulary and that you didn't misread the name of the DIVE : element. : : Without a controlled vocabulary, a name space is, at best, a private : agreement among a bunch of people about what the names are (and : possibly how to interpret things with those names), at worst it's : just a mishmash of no reliable value. There's nothing wrong with : private agreements, but there doesn't seem to be much point in : creating a *standard* designed to enable *interchange* that doesn't : provide for *public* agreements. : : For example, if some company starts using a name space prefix but : doesn't define its vocabulary in some standardized way (so that any : conforming tool can interpret it and validate against it), how can : you ever know if you've handled all their names if you're tryin to : compete with them by providing support for their data elements? You : can't. : : In addition, how can this company prevent others from spoofing its : name space? For example, a competitor could cause its tool to : produce documents that used the company's name space with names that : the company hadn't defined. When user's complained that the : company's tool didn't read the documents produced by the : competitor's tool, the competitor could claim that it's not their : fault, the names are in the company's name space and they should : handle them. This probably seems far fetched, but it could happen : (or something more devious and clever). In any case, the user would : have no way of knowing which company was lying. "Follow The Money". It was scripted a long time ago... Arjun 
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