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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] the "upwards funarg" problem.
 The notion would appear to abound on this list, that the matter of universal names, the modeling of same and techniques for syntactic minimization in serialization are somehow uncharted waters. The behaviour of qualified name prefixes in the DOM is but one example. Is it a problem to associate prefixes with names in the DOM? If so, then under which circumstances, and how is the problem resolved? The answer to each question is clear. Not only that, it would appear that the answers have been known for close to forty years. As I have noted in previous posts, this is an instance of the "upwards funarg" problem. Since I was curious about the history of this concept, I launched a request (http://www.hotbot.com/?MT=upwards+funarg&SM=phrase&DV=0&LG=any&DC=25&DE=2&submit=SEARCH&_v=2&OPs=MDRTP) which yielded only two results. as chance would have it, they were two quite pertinent results. the first reference was (http://www.stanford.edu/class/cs242/Autumn1997/outlines-95/funarg.html) it describes succinctly the issues which one needs address when referring to non-local, but lexically apparent, variable bindings in systems which permit first class functions. this is the "upwards funarg" problem. if the term means nothing to you, that note will explain enough for you to recognize the problem in the prefix<->URI bindings which may appear in DOM elements. The key is to note that the prefix acts as a lexically apparent binding for a URI over which a child element closes whenever it comprises a name which is qualified by the given prefix. (Should the duality between closures and objects be a missing link here, then take note of graham's exposition in chapter 17 of "ansi common lisp", in which he demonstrates how to model objects with closures, and invert it.) Given this analogy, when one transplants in the DOM an element which "closes over" some prefix binding, one is performing an operation analogous to passing a first class function upwards through an invocation stack. If one does not model this operation correctly this can lead to unintended results. (see ms Fisher's description at the location noted above for the synopsis.) As noted before, there are some who believe that such closures never come into existence, as the prefix stands in no direct relation to the respective names, but if one insists on such a model for names, then one must handle this problem. the second reference was to a chance note in comp.compilers (http://cuisg11.unige.ch/OSG/people/jvitek/Compilers/Year95/msg00974.html) which indirectly cites what would appear to be the first publication of the mechanisms for modelling problems of this sort: an article in Communications of the ACM, from 1973. The comp.compilers note also makes the point that, although this article constituted a publication milestone, the issue was addressed in implmentations which dated much earlier. Among them is Lisp 1.5. I somehow had dated Lisp 1.5 to the late sixties. When I looked further, I noted that for which the prorgammers's manual was published in 1961 and, as described in (http://www8.informatik.uni-erlangen.de/html/lisp/mcc91.html) the initial work on it - including the funarg problem is described in memos from the MIT AI-Lab from as early as 1959. ... 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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