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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: SAX and delayed entity loading
 At 10:12 AM 12/3/98 -0600, W. Eliot Kimber wrote: >At 09:30 PM 12/2/98 -0500, david@m... wrote: >>I think that notations and unparsed entities in XML have proven >>themselves to be non-starters. They worked well in the SGML and have >>done me good service, but MIME types and hrefs provide the same >>functionality (if somewhat weaker validation) and they work with or >>without a document type declaration. > >I can't agree with David's statement that MIME types and hrefs provide the >same functionality as notations and external data entities. They are >similar, but weaker: I definitely agree with David's statement, and would frankly make it stronger. Notations and unparsed entities make sense only if you want all information regarding resources to be stored in the document, with no reliance on outside assistance. (For example, HTTP provides MIME type headers on its transfers.) If this isn't the case, notations and unparsed entities are a nuisance, providing functionality that duplicates that provided by other tools in a format all its own. > >1. href provides no indirection mechanism... >By concentrating the mapping of local names to storage objects >in the document prolog, processors (and authors) do not need to scan an >entire document to know what the doc-to-entity dependencies are. For small >docs this doesn't really matter, but for very large docs, this can be a >significant savings. >... Inline hrefs can't do this directly, but similar functionality and management can be provided through XLink, using hub documents to provide links rather than keeping all links inline. >2. Notations provide a richer degree of data type specification that is >more flexible and more generally applicable than MIME types... Perhaps, if you're creating your own notations on a regular basis. MIME types are quite flexible, however, especially if you don't mind declaring them as x-whatever. The main point remains that MIME types work well for Web-type situations where other facilities outside the document are capable of describing entities as richly and as completely, with less upkeep, than notations inside a document. >For example, >how do you apply a MIME type to an element or attribute? For the element, I could do it with a plain old CDATA attribute or with an external document specifying what element should be processed how. How would I apply a MIME type to an attribute? More important, why one earth would I want to? Seems like some pretty heavy overkill. >Of course, the use or non-use of entities and notations is a data >management choice that has to be made on a case-by-case basis. There are >certainly classes of document for which the indirection of entities does >not provide sufficient benefit to justify the cost. But that isn't the case >for all XML documents. Of course it's up to the user - but a lot of things would have been a lot simpler if XML had just plain excised this redundant and complicated 'feature' in favor of a style that better reflects its intended use on the Web. It may be worthwhile for users who do need to keep all that information in the document, and therefore worth keeping, but... what a headache... >So saying that entities and notations are non-starters is, I think, a bit >strong. Personally, I'd say it's a bit weak and declare them a menace or at least a nuisance, but as I mentioned above there may be cases where this information needs to be included in documents. Other application-level facilities would probably have been as capable, but it's there now... XML is SGML simplified enough to be useful to a wider audience, but there are many times I wish it had been simplified considerably further. (That way, when we go to add all these new features, they aren't all redundant, among other things.) Simon St.Laurent XML: A Primer / Cookies Sharing Bandwidth (December) Building XML Applications (January) http://www.simonstl.com xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...) 
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