BKLRNXML.RVW   20010708

"Learning XML", Erik T. Ray, 2001, 0-596-00046-4, U$34.95/C$51.95
%A   Erik T. Ray
%C   103 Morris Street, Suite A, Sebastopol, CA   95472
%D   2001
%G   0-596-00046-4
%I   O'Reilly & Associates, Inc.
%O   U$34.95/C$51.95 800-998-9938 fax: 707-829-0104 nuts@ora.com
%P   350 p.
%T   "Learning XML: Creating Self-Describing Data"

XML (eXtensible Markup Language) is currently being seen as the cure
for all the ills (and incompatibilities) of the Web, and, by extension
(sorry), for information technology as a whole.  Why this might
happen, and how XML might be used, is not often made clear.

Chapter one is enthusiastic and up-beat--but not very specific.  We
are told that XML allows you to describe data, and to create new data
structures, but then again, pretty much every computer language ever
invented does the same thing.  We are told that it performs functions
similar to SGML (Standard Generalized Markup Language) and that, in
fact, XML is a reduced version of SGML, but we are not told why SGML
was too big, nor what we might be giving up in moving to XML.  We are
not given any useful example of what we might do with XML: in fact,
the only realistic example in the chapter uses MathML (Math Markup
Language).  And the chapter ends by basically outlining the fact that
nobody really supports XML yet.

Chapter two provides clear examples of XML syntax and requirements,
but only at a basic level.  (For example, does the use of compound
documents help with the use of multiple namespaces, or just make the
problem worse?)  There is, finally, an example of real XML using the
Barebones DocBook application.  Links are dealt with in chapter three. 
XLink is clear, though brief, with recognizable definitions of HTML
image and anchor tags.  The explanation of XPointer is more confused,
and the section concludes with an example of strict XHTML (eXtensible
HyperText Markup Language) which doesn't seem to fit the topic at all. 
Presentation and stylesheets are covered in chapter four,
concentrating on the Cascading Style Sheets (CSS) model.  Chapter five
examines two types of document models, spending most of the time
explaining DTDs (Document Type Definitions) and then briefly looking
at XSchema.  While transformations are supposed to be the topic of
chapter 6, the point is not really clear, and the text seems to deal
primarily with XSLT (eXtensible Stylesheet Language for
Transformations) simply as a special case of XSL (eXtensible
Stylesheet Language).  Internationalization is limited to the fact
that you can specify encoding and language, in chapter seven.  Chapter
eight, on programming for XML, contains Perl code for a parser and
syntax checker.

This book is a good introduction to XML, and the various related
technologies.  It is difficult to say that, by the end of the work,
you will actually have learned XML, but that has more to do with the
current amorphous state of the technology than any fault in writing.

copyright Robert M. Slade, 2001   BKLRNXML.RVW   20010708