As of: Thu 2010-09-02 18:05:55 UTC [=1283450755. 14:05:55-04:00]
>> heuristic.sgm L: 15,077. A: 100444. M: 1999-06-01 18:55:31 UTC [=928263331] -4110.96d >>
<!-- Note: this line is an SGML comment -->
<!-- Note that all SGML markup is human-readable: no unprintables -->
<!DOCTYPE heuristic [
<!ELEMENT heuristic - - (purpose, inote?, realization, docinfo)>
<!-- The "top level" element for a -->
<!-- document structured according -->
<!-- to this DTD is: "heuristic". -->
<!-- The "heuristic" element must -->
<!-- contain exactly one "purpose" -->
<!-- element, optionally followed -->
<!-- by an "inote", obligatorily -->
<!-- followed by one "realization" -->
<!-- element, followed by one -->
<!-- "docinfo" element, and -->
<!-- nothing else! -->
<!ATTLIST heuristic
version CDATA #FIXED "1.52"
security (unrestricted | internal.use | confidential |
need.to.know) #REQUIRED >
<!ELEMENT purpose - - (#PCDATA) >
<!-- "#PCDATA" means: parsable -->
<!-- character data, i.e., text -->
<!-- in which the "<" character -->
<!-- is treated as a start-of- -->
<!-- tag character, etc. -->
<!ELEMENT inote - - (#PCDATA) >
<!ELEMENT realization - - (point+) > <!-- a "realization" -->
<!-- consists of 1 or more "points"-->
<!ELEMENT point - - (title, text+) > <!-- a "point" -->
<!-- must contain one "title", -->
<!-- followed by 1 or more "text" -->
<!-- elements -->
<!ELEMENT title - - (#PCDATA) > <!-- a "title" element -->
<!-- can contain only characters, -->
<!-- with no further embedded -->
<!-- elements -->
<!ELEMENT text - - (#PCDATA) +(quote | institution | ruler |
list | product | link | country) >
<!-- a text element can contain -->
<!-- zero or any number of quote, -->
<!-- institution, ruler, list... -->
<!-- elements, as well as -->
<!-- character text.... -->
<!ELEMENT docinfo - - (url, author, auth.eaddr, rev.date) >
<!ELEMENT url - - (server, account, page.id) >
<!ELEMENT server - - (#PCDATA) >
<!ELEMENT account - - (#PCDATA) >
<!ELEMENT page.id - - (#PCDATA) >
<!ELEMENT author - - (given.name,sur.name,credential*) >
<!ELEMENT given.name - - (#PCDATA) >
<!ELEMENT sur.name - - (#PCDATA) >
<!ELEMENT credential - - (#PCDATA) >
<!ELEMENT auth.eaddr - - (#PCDATA) >
<!ELEMENT rev.date - - (rev.yr, rev.mo, rev.da) >
<!ELEMENT rev.yr - - (#PCDATA) >
<!ELEMENT rev.mo - - (#PCDATA) >
<!ELEMENT rev.da - - (#PCDATA) >
<!ELEMENT quote - - (#PCDATA) +(quote | institution |
product | ruler | country) >
<!ATTLIST quote
type (copied.text | hearsay | memory | ipse.dixit |
idiom | fictive | text.as.object |
other) #REQUIRED
source CDATA #IMPLIED >
<!ELEMENT link - - (#PCDATA) >
<!ATTLIST link
tgt CDATA #REQUIRED >
<!ELEMENT institution - - (#PCDATA) >
<!ATTLIST institution
type (corp | school | other) #REQUIRED >
<!ELEMENT product - - (#PCDATA) >
<!ELEMENT ruler - - (#PCDATA) >
<!ATTLIST ruler
type (king | prince | queen | president |
prime.minister | other) #REQUIRED >
<!ELEMENT country - - (#PCDATA) >
<!ELEMENT list - - (item+) >
<!ELEMENT item - - (#PCDATA) +(quote | institution |
product | ruler | list) >
<!ELEMENT i - - (#PCDATA) >
<!ENTITY % THINK "include" >
<!ENTITY % TAGS "ignore" >
<!ENTITY % NOTAGS "include" >
<!ENTITY lt "<" >
<?STYLESPEC "Style1" "heuristic.ssh" >
]>
<!-- document instance -->
<!-- Note: this line is an SGML comment -->
<heuristic security="unrestricted">
<purpose>This page aims to introduce you to <![%THINK;[SGML]]>
</purpose> <!-- Note: the slash ('/') is SGML's "end-of-element" -->
<!-- indicator. E.g., the /purpose tag ends the -->
<!-- purpose element, and the text between the -->
<!-- two tags is the content of the purpose element -->
<![%NOTAGS[<inote>When this document is formatted for display
as an HTML web page, with all the SGML structure-describing tags
reduced to HTML style-descriptors (with, in some cases, the tagging
just being discarded and not translated into anything...), it
looks nicer, but information is lost.</inote>]]>
<realization>
<point>
<title>What is the idea of SGML?</title>
<text>The idea of SGML is to thematize the structure of text, by
adding explicit structure descriptors -- markup tags -- to the text.
For example, if we wish to communicate something about a product,
instead of saying something like: "Netscape's Navigator is not
related to Portugal's Henry the Navigator", we can say:
<quote type="fictive"><institution type="corp">Netscape</institution>'s
<product>Navigator</product> is not related
to <country>Portugal</country>'s <ruler type="prince">Henry the
Navigator</ruler>.</quote> <![%NOTAGS;[Note that, in the
preceding sentence, when the structure tags are reduced to simple
HTML page formatting, the tagged up sentence looks pretty much
the same as the untagged plain text version.]]></text>
<text>Texts, like physical buildings, can either be products of habit
and custom (<quote type="idiom">vernacular architecture</quote>), or
be products of conscious, self-accountable creativity and critique
(<institution type="school">The Bauhaus</institution>, structural
engineering, etc.). I hypothesize SGML may portend
a <quote type="memory" source="Henry Adams">change of phase</quote>
in our relation to language, such as previously was effected by
alphabetic writing and uniform printed editions. Among other things,
SGML is what <quote type="idiom">diagramming sentences</quote>
in high-school English should have been but wasn't: SGML realizes,
as effective and proactive social activity, and not merely as
social-scientists' dissociated theorizing, a notion
of <quote type="idiom">generative grammar</quote>!
</text></point>
<point>
<title>What is the value of adding explicit structure descriptors
to text?</title>
<text>The rewards of adding explicit structure descriptors to text
are many, including:
<list>
<item>Stimulating reflection on the logical structure of what one
is saying, leading to:
<list>
<item>Better style: Making what one is trying to say clearer
to the persons who will read and try to understand it</item>
<item>Clearer thinking: Forcing oneself to become clearer
what one is trying to say</item>
<item>Discovery: Discovering things about both the content and
the form of expression which one had not previously thought
of, through the process of articulating what one thinks
one wants to say</item>
</list></item>
<item>Facilitating computer programs to process the text (it's much
easier for a computer program to find all the references to rulers
of countries if they are all labelled something like:
<quote type="text.as.object"><ruler type="..."> ... </ruler></quote>,
than if their names simply appear -- like the reference to Henry
the non-Netscape Navigator in this sentence -- as undistinguished
sub-strings of homogenous character strings.</item>
</list>
</text></point>
<point>
<title>Once you've "tagged up" your text with these structural
descriptors, what can you do with it?</title>
<text>Adding structural descriptors to text is the first step of what,
in general, is an at least two-step process. Persons do not generally
directly read the tagged text<![%TAGS;[ (e.g., what you are here
reading now...)]]>. What generally happens is that one also
writes a <quote type="idiom">style sheet</quote>, which a computer
program reads, along with the tagged text file: The computer program
then generates a formatted document, as paper printout, online web
pages [<link tgt="heuristic.html">see example</link>], spoken text
for the blind, etc.</text>
<text>One of the benefits of SGML is that, once you have produced
your tagged text document, which, in a sense, has no format (other
than being a human- and computer-readable ASCII text file), anyone
can generate output in any desired form, by simply writing different
style sheets for appropriate processing programs. Example:
In a hospital, insurance providers, oversight groups, doctors
and nurses, patients themselves, and others perhaps not yet
foreseen, may wish to examine patient records in all
sorts of different ways. If the hospital maintains its patient
records in SGML, then everybody can put the data into the form
they want, without the hospital having to do anything except make
the raw source data available. If a doctor wishes to see patient
information on a palm-top computer, the data can be transformed
by a web browser (or browser plug-in, such
as <institution type="corp">SoftQuad</institution>'s <product>Panorama
Viewer</product>), into display pages, even selecting only the
particular kinds of data of interest to the doctor (e.g., the course
of symptoms, but not billing information). An insurance provider,
on the other hand, can download the billing information over a
high-speed data link, and either process it as-is, or run it through
a program which loads it into their database management system (DBMS).
</text></point>
<point>
<title>What is an SGML document like, exactly?</title>
<text>You have been looking at an SGML document all the time you
have been reading this. An SGML document consists of two parts:
<list>
<item>A document type description (DTD). A DTD defines the
pattern for a certain kind of document. It specifies what
kind of elements can exist in a document coded according to
its logical form, which of those elements can be contained
in which other elements, and the order in which different
elements must occur. The present document's
DTD [<link tgt="#DTD">see above</link>] specifies that
quotes can appear in text elements, but not (e.g.) in titles
or in the document's meta-document information (the
<quote type="text.as.object">docinfo</quote> element).
On the other hand, an author element can only occur inside
a docinfo element, there must be one and only one author
element, and it must immediately follow a url element
in the docinfo block....</item>
<item>The document instance itself, i.e.: the text, tagged to
explicitly articulate its structure according to the
specified document type description.</item>
</list>
Note that a given document type description (DTD) can be used as a
template for an indefinite number of document instances (to
facilitate this, the DTD is generally kept in a separate computer
file, apart from the document instances which use it).</text>
<text>Also note that, if, as is generally done, one edits
one's document using an SGML-aware text editing program (such
as <institution type="corp">ArborText</institution>'s
<product>AdeptEditor</product>, the text editor can make sure the
document instance conforms to its type, by not permitting entry of
elements (tags) except where they are allowed. Conversely, such an
editor can aid the writing process -- possibly even helping
overcome writers' blocks -- by telling the writer what kinds of
items can be entered at any place in the document being edited.
</text></point>
<point>
<title>But isn't SGML a straitjacket, then?</title>
<text>No! SGML is not like a straitjacket (or even like dictionaries
and grammar books), because you can create your own document type
definitions (DTDs), and, as you write your documents according to
a DTD you have created, if you find it doesn't let you do what you
want the way you want to do it, you can change the DTD to make it
more suited to your purposes. A side-effect of this process is that,
because every change you make must be explicitly declared in your
DTD, you always have an up-to-date record of your conception of your
document's structure, without having to make any extra effort to
write extrinsic documentation. A well-written SGML document
largely documents itself!
</text></point>
<point>
<title>What's the difference between SGML, HTML, and XML?</title>
<text>HTML looks like SGML, but HTML tags are mostly style
descriptors rather than structure descriptors. Example: the
HTML <quote type="text.as.object"><b></quote> tag says:
make the following text appear in bold-face. The HTML
<quote type="text.as.object"><address></quote> element, on
the other hand, is an example of a structure-describing tag: it
doesn't prescribe what the text it contains is supposed to look
like, but rather it articulates what that content means.</text>
<text>XML is a simplified, <quote type="idiom">dumbed-down</quote>
variant of SGML. XML tags should generally be structure-describing,
but SGML is functionally much richer than XML. Also, XML does not
require an explicit document type (document structure) specification
(DTD). This makes XML easier to code, but it also provides less
motivation and assistance to think about the structure of one's
document, since, in an XML document instance, you can make up new
(or inconsistent) elements as you go along, e.g., calling a
quotation here a: <quote type="text.as.object"><quote></quote>,
there a: <quote type="text.as.object"><quotation></quote>,
elsewhere a: <quote type="text.as.object"><quot></quote>, etc.
</text></point>
<point>
<title>Conclusion</title>
<text>To paraphrase Martin Luther:
<quote type="memory">A mighty fortress is our SGML!</quote>
</text></point>
</realization>
<docinfo>
<url><server>www.cloud9.net</server><account>bradmcc</account>
<page.id>WhatIsSGML.html</page.id></url>
<author><given.name>Brad</given.name><sur.name>McCormick</sur.name>
<credential>Ed.D.</credential></author>
<auth.eaddr>bradmcc@cloud9.net</auth.eaddr>
<rev.date><rev.yr>1999</rev.yr><rev.mo>06</rev.mo>
<rev.da>01</rev.da></rev.date>
</docinfo>
</heuristic>
<< heuristic.sgm L: 15,077. A: 100444. M: 1999-06-01 18:55:31 UTC [=928263331] -4110.96d <<
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