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Newsgroups: comp.text.sgml Subject: NOT the comp.text.sgml FAQ Followup-To: poster From: Joe English Archive-Name: sgml/not-the-faq Posting-Date: 1 April 2002 Posting-Frequency: sporadic ============================================================ Not the comp.text.sgml Frequently Asked Questions List ============================================================ Copyright (C) 1997, 1999, 2001, 2002 Joe English. All rights reserved. There are lots of wrongs in this document, and those are all reserved too. Author bears no responsibility for any other reservations you might have. Standard disclaimers apply. For external use only. If irritation, rash, or swelling occurs, discontinue use immediately. Void where prohibited. If you are acquiring this document on behalf of the U.S. Government, the Government shall have only "Restricted Rights Regulated Regulations Rights" (RRRRRs) as defined in Clause 31.415.269 (c) (2) (CCXXXVII) of that really long document that nobody has ever seen or read and good luck finding it (US-DOD-MILSPEC-217-RLDTNHESOR-AGLFI-YOG-SOTHOTH-1968), pursuant to the following: (1) Who are you? (2) What do you want? (3) Who do you serve, and who do you trust? (4) Where do you want to go today? Notwithstanding the foregoing, the author grants permission to anyone who has actually read this far into the disclaimer and copyright notice to do whatever they want with the damn thing. ============================================================ Part 1. Administrivia. ============================================================ Q. Is there a FAQ for this newsgroup? A. Yes. This is not it. Q. In the real FAQ, how come all the answers just point to ? A. If you've ever tried to get more than four SGML experts to agree on the answer to _any_ question, you'd understand. The only thing that every expert agrees on is that Robin Cover's web site is the best source of SGML information available anywhere. Q. I saw this last year. Can you tell me what's new in this year's edition so I don't have to slog through the whole thing again? A. No. Save a copy of this article so next year you can run 'diff' on it. ============================================================ Part 2. SGML, HTML, and XML. ============================================================ Q: In what way is XML simpler than SGML? A: Nearly everyone who has ever adopted an SGML-based system will agree that the hardest part of the project is the initial set-up. This process often requires highly-paid consultants, who spend weeks or even months analyzing requirements. The principal end result of this process is: a DTD. Since XML does not require DTDs, it is hoped that companies who adopt XML instead of full SGML can skip this expensive and time-consuming step. Q. Why does XML require SYSTEM identifiers after all PUBLIC identifiers? A. Since there is as of yet no standardized resolution mechanism for PUBLIC identifiers, XML requires authors to supply a URI for every external entity so that it will always be possible for clients to retrieve the entity. More information can be found on the WWW consortium's web site at www.cern.ch^H^H^H^H^H^Hmit.edu^H^H^H^H^H^H^Hw3.org, or at Robin Cover's excellent XML/SGML web page at www.sil.org^H^H^H^H^H^H^Hoasis-open.org/cover/. Q. Even in  declarations? I thought XML was designed to be usable without DTDs. A. A PUBLIC identifier on it's own doesn't do anybody any good unless they can reliably resolve the entity. You must provide a URI, so that document consumers can retrieve the DTD if they so choose. Q. I have a document that has a whole bunch of "xmlns:foo='http://...'" attributes in it. What are all these URLs supposed to point to? A. Erm... ============================================================ Part 3. SGML, XML, and the Web. ============================================================ Q. I'm looking for the HTML DTDs used by the current versions of Netscape Navigator and MSIE. Where can I find them? A. This has the editor stumped. I can't think of an answer that's funnier than the original question. Q. How do I includ

we're zany to the max

JDAHA'I >=&#6C;&#6F;&#6E;AO E&#6E; &#6F;KH I&#6C;=?&#6B;I The first example is clearly much more readable than the second. UPDATE: This situation has changed since the Standard was first published. Thanks to the widespread availability of Unicode tables, most people nowadays find the hexadecimal form to be quite legible. A recent amendment adds this capability to SGML. (XML has always allowed it, since it wasn't designed to be read by humans.) Q. Why does nsgmls complain that '((a|b)*,b)' is ambiguous? A. Because it's not clear whether 'a' stands for Anchor, Author, or Address. Q. OK, so how do I make it unambiguous? A. This depends of course on the content model in question. Your best bet is to post to comp.text.sgml, where you are likely to receive several answers. Many will be wrong, so don't take any advice from the newsgroup unless three or more respondents say the same thing. Q. What's an RE? A. RE is an acronym for Record End, which is sort of like a newline, only different. Goldfarb's First Law of Text Processing states that: "... if a text processing system has bugs, at least one of them will have to do with the handling of input line endings." [The Handbook, footnote p. 321] The Record End concept was introduced to make sure that SGML parsers don't violate Goldfarb's First Law. Q. So what's an RS? A. An RS is a fictitious character inserted by the entity manager and later removed by the parser. Applications shouldn't ever have to worry about RSs; their primary function is to make REs disappear in mysterious places. Q. What's the difference between a QUANTITY and a CAPACITY? A. In the SGML declaration, a "quantity" is an arbitrary limit placed on the size of individual parts of a document which must be increased in order to use reasonable DTDs. A "capacity" on the other hand is an arbitrary limit placed on the size of the document as a whole which must be increased in order to process reasonably-sized documents. Quantities and capacities are used to make sure that every document includes an SGML declaration. Were it not for the ridiculously small limits in the Reference Concrete Syntax, most SGML users would be able to simply use the default SGML declaration instead of providing their own, slightly modified version, in violation of section 6.2. Q. What are inclusion exceptions and how do they work? A. There are two primary schools of thought regarding inclusions. Some feel that inclusion exceptions are a dangerous and badly designed feature, and should never be used (exclusion exceptions, however, are another matter). Others feel that inclusion exceptions are a useful and necessary enhancement to SGML's formal model. Q. What are exclusion exceptions and how do they work? A. There are two primary schools of thought regarding exclusions. Some feel that exclusion exceptions are a dangerous and badly designed feature, and should never be used (inclusion exceptions, however, are another matter). Others feel that exclusion exceptions are a useful and necessary enhancement to SGML's formal model. ============================================================ Part 7. HyTime. ============================================================ Q. What's a grove? A. I've heard that it's supposed to be an acronym for some thing or another, but I don't buy it. Q. What's the difference between a 'wand' and a 'baton' in the HyTime scheduling and rendition module? A. Sorry, it took me three months just to figure out 'pathloc'. I'm not even going to try to answer that one. Q. How many HyTime consultants does it take to screw in a lightbulb? A. Just one. HyTime's powerful linking and location facilities make it trivial to create a link expressing the abstract semantic of "screwing" with the lightbulb and the socket as link-ends, and even if the lightbulb and socket are not expressed as SGML objects you're free to use whatever application-specific query notation you desire to locate them. The actual installation of the light bulb is, of course, left up to the application. ===============================