The magazine of the Melbourne PC User Group XML - for the bookshelf Major Keary |
The importance of XML ̶ eXtensible Markup Language — cannot be overestimated. In development are a large number of XML-based initiatives designed for doing business over the Internet. Originally conceived as a replacement for HTML, XML has been developed to the point where it "offers the tantalising possibility of truly cross-platform, long-term data formats" [XML in a Nutshell]. There is increasing enterprise-level reliance on XML and its technologies to ensure permanence of data and access to it. Computer end-users are often unaware that applications they use from day to day make use of XML: OpenOffice stores its files in XML format, and Microsoft Office 2003 can write to XML (but still saves in a binary format by default).
Not many present-day users will have ever seen, let alone used, an 8-inch floppy disk. Suppose you are given such a disk that contains document files created by the original CP/M version of WordStar; unless you can find a copy of WordStar and a machine that can run the program and which has an 8-inch drive, it's a case of being up the creek without a paddle. That fate awaits files saved in MS proprietary binary format. Given that the means to read the media are available, OpenOffice files (like the source files created for TeX) will remain readable because, even if the program is extinct, writing a parser is trivial (at least, for those who know what they are doing). TeX files created in the late 1970s are still valid, even though they are processed on and with equipment that was not even a gleam in the engineer's eye thirty-five years ago. The same goes for files created using the Standardized General Markup Language (SGML), of which XML is a subset.
Users of digital photography with an eye to posterity should consider the problem images stored in binary format, especially in CD-based archives. What happens when CD drives have become redundant? Will there be software that can read today's recording formats and media, let alone graphics formats? Photographs taken during the American Civil War are still available to us; will yours still be around — and usable — in 150 years time? However, that's another subject; the topic here is XML and its applications, which are moving towards development of long-term, cross-platform data formats.
Learning XML
Now in its second edition, Learning XML has been expanded to include schemas ('A schema is any type of model document that defines the structure of something, such as databases or documents" [Beginning XML]). This text provides an excellent
coverage of XML:s foundations and the technologies that have been developed for particular needs. It is the definitive introduction to XML.
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Erik Tay: Learning XML 2/e ISBN 0-596-00420-6 Published by O'Reilly, 400 pp., RRP $85.00 incl. GST |
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XML in a Nutshell
Now in its third edition, this is the definitive guide and reference for
developers. The first half of the book is divided into sections that discuss:
XML Concepts (XML fundamentals, DTDs, namespaces, and internationalisation);
Narrative-Like Documents (XML as a document format, XML on the web, XSLT, XPath,
XLinks, XPointers, Xlnclude, cascading style sheets, XSL formatting objects, and
the Resource Directory Description Language); Record-Like Documents (XML as a
data format, schemas, programming models, DOM, and SAX).
The second half the book is a reference section that contains succinct entries —
that include examples of
syntax and use — covering the W3C recommendations for XML, schemas, XPath, XSLT,
DOM, SAX, and character sets with Unicode coding.
Information is easy to find with a detailed table of contents, 34-page index,
and a convenient thumb index. The writing is excellent, although this, "... the
markup has less semantics to lever off of.", took me by surprise. It must have
slipped past the usually eagle-eyed O'Reilly editorial staff.
An essential reference for web designers, programmers using applications such as
REST and SOAP, and developers involved in internationalisation of applications,
web pages, and other situations where language encodings are required. A title
that should be in any library.
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Elliotte Harold and W. Scott Means: XML in a Nutshell 3/e ISBN 0-596-00764-7 Published by O'Reilly, 689 pp., RRP $79.95 in GST |
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XML Hacks
Just released in the hacks series, this title presents "100 Industrial-Strength
Tips & Tools" for XML users. Apart from the working hacks, the author gives the
reader glimpses of XML technologies that are in development.
The hacks are grouped under categories: Looking at XML Documents
(reading, displaying, character entity
references, XML vocabulary tools, Java
programs that process XML); Creating
XML Documents (includes editing
tools, using OpenOffice
as a conversion tool,
create an XML document from a CSV file;
Transforming XML Documents (includes XSLT,
convert XML to CSV,
generate" XML from
SQL, generate PDF
documents from XML
and CSS, perform math
with XSLT, generate SVG
with XSLT); XML Vocabularies (namespaces,
create and validate XHTML documents, identify yourself with FOAF, the OpenOffice
file format, using XForms, create technical manuals and papers in XML with
DocBook); Defining XML Vocabularies with Schema Languages (validation issues);
RSS and Atom (one of the hacks shows how to syndicate a list of books from
Amazon with RSS and ASP); and Advanced XML Hacks.
Illustrations (mainly screen shots) are used sparingly to support the text, and
there are plenty of code examples (which are also available for download from a
Web site).
Even though the book is a valuable resource intended for users who know their
way around XML technologies, it also provides a fascinating insight for those
who would like to know more about XML and its capabilities.
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Michael Fitzgerald: XML Hacks ISBN 0-596-00711-6 Published by O'Reilly, 460 pp., RRP $49.95 incl. GST |
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Beginning XML
Wrox Press puts all its efforts into content; their titles typically have
multiple authors (and not just two or three), and are information dense — both
in the sense of what they pack in, and in the sense of space (pages are
wall-to-wall text). Given the number of contributors, I am always surprised by
the uniformity of style achieved.
Beginning XML is a book for programmers written by programmers (nine of them)
and is in much the same mould as an academic 'introduction': readers are
expected to know things or be capable of finding information for themselves. In
short, this is not a primer. The intended audience includes programmers familiar
with some Web programming or data interchange techniques, and those who work in
a programming environment but have no experience of Web development or data
exchange. Readers
are not expected to know anything about XML, SGML, or markup languages at large.
So, if you can cope with terse entries such as,
Input Functions
At the time of writing, the XQuery input functions are the doc () function and
the collection ( ) function and both are implemented in Saxon 7.8.
this book is for you. However, that is not typical of the content; it occurs
frequently, but there is also extensive discussion of concepts, especially in
the introductory chapters. At the end of each chapter there are self-test
questions, with answers in an appendix.
Of particular interest to database users and developers is a chapter on XQuery,
which "provides a powerful mechanism to pull XML content from multiple sources
and dynamically generate new content using a user- friendly declarative
language" ]XML Hacks]. XQuery can be compared to SQL; it is described — albeit
tersely — in more detail here than will be found in other current literature.
This is a hefty, and most comprehensive, overview of XML technologies. It is
especially suited to people wanting a self-study introduction, even though the
specific audience is programmers who want to learn XML — for them it provides
the kind of compact, detailed information they need.
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David Hunter et al.: Beginning XML 3/e ISBN 0-7645-7077-3 Published by Wrox Press, 995 pp., RRP $66.95 incl. GST |
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Reprinted from the August 2005 issue of PC Update, the magazine of Melbourne PC User Group, Australia
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