Perl & XML

dooling writes: "Perl & XML is a well-written book that accomplishes what it sets out to do. It states in the preface that it is written for Perl programmers who want to learn about XML and what is available in Perl for XML processing. It achieves this goal, but little else. When you are done reading this book you will have been given an overview of Perl and XML, know where to begin to attack an XML document, and know where to look to find more information." For dooling's more complete review, read on below. Perl & XML author Erik T. Ray & Jason McIntosh pages 202 publisher O'Reilly and Associates rating 6 reviewer dooling ISBN 059600205X summary Good introduction to XML for Perl programmers.

The book starts out with a brief explanation of why XML and Perl are well-suited for each other. It then provides a teaser of things to come: an explanation of how to use the XML::Simple module. The first chapter concludes with some warnings and gotchas that seem a little premature since they have not really explained XML. Fortunately, most of these gotchas are covered in context later in the book.

The second chapter provides a whirlwind overview of XML -- covering its structure, DTDs, schemas, and XSLT (transformation). The discussion of XML in general, its history, and parts of an XML document are well done. They give someone who is familiar with static HTML the needed background to understand the structure of an XML document and the vocabulary used to describe it. Unfortunately, the discussion of where XML begins to distinguish itself from HTML, namely with DTDs, the new replacement for DTDs called schemas, and the transformation language XSLT, is too brief. They gloss over these topics with little explanation and few examples. That said, there are other books that do provide more in-depth coverage of XML (this book only promises an introduction).

The next five chapters cover Perl modules designed to process XML, starting with simple parsers and writers. Only methods and syntax relating to XML processing are explained. Therefore, if you are considering reading this book, you should be fairly comfortable with Perl and object-oriented (OO) interfaces to CPAN modules (nearly all the modules discussed provide OO APIs). Again, there are other books and perldoc documentation that cover Perl and it's OO features; so read them first if you are not familiar with OO Perl. If you are familiar with OO Perl, these chapters provide a good overview of the different ways XML can be processed (stream- and tree-based approaches), the advantages and disadvantages of each, and the Perl modules best suited for each approach. These chapters are the biggest strength of this book. The modules discussed in these chapters are by no means an exhaustive list of XML-related modules available from CPAN nor do the explanations of each module cover everything the module does. These chapters do, however, provide the reader with enough information that she can begin to process XML documents intelligently and know where to turn when she needs more information.

The next chapter, Chapter 8, covers XML tree iterators, XPath, XSLT, and XML::Twig. All of these topics are covered in a span of 16 pages (with only slightly over two pages dedicated to XSLT). Indeed, after reading the chapter, you may get the feeling that it was only included so the authors could cram more trite colloquialisms into the book. The short shrift given to these topics creates the impression, which is strengthened in the chapters that follow, that this book was rushed a bit to press.

Chapter 9 discusses applications of XML, including RSS and SOAP, and Chapter 10 is mostly example code. These chapters are intended to give you a feeling for what is possible without really giving you enough information to make it happen. The main problem with these chapters are the examples: the examples are long and the explanations are short. Thus, they are more useful as templates or a quick reference than for learning these topics in detail. Of course, the authors never promised you would be programming SOAP applications when you were done reading this book. And again, there are other books out there which discuss these topics in more detail. So the authors stay true to their promise throughout the book: they will introduce you to XML and tell you how to interact with XML using Perl, no more.

Personally, I found this book did, in general, give me enough information to get started using XML and pointed me where I needed to go to get more information. I am an experienced Perl programmer who is new to XML and comfortable with on-line documentation. This book seems to be written for people who fit this profile and who want to learn by doing (finding the answers to the "hard" questions as they arise). It does introduce a wide variety of XML-related topics and the Perl modules used to interact with them, which is what the authors promised to do in the preface. While it is by no means an authoritative text on Perl and XML, there is something to be said for keeping promises ...

Index As with most first-edition books, the index was adequate but not complete. For example, XML::Twig, which has an entire section covering it, does not appear in the index at all.

Contents
Preface

1. Perl and XML
2. • Why Use Perl with XML?
   • XML Is Simple with XML::Simple
   • XML Processors
   • A Myriad of Modules
   • Keep in Mind ...
   • XML Gotchas
3. An XML Recap
4. • A Brief History of XML
   • Markup, Elements, and Structure
   • Namespaces
   • Spacing
   • Entities
   • Unicode, Character Sets, and Encodings
   • The XML Declaration
   • Processing Instructions and Other Markup
   • Free-Form XML and Well-Formed Documents
   • Declaring Elements and Attributes
   • Schemas
   • Transformations
5. XML Basics: Reading and Writing
6. • XML Parsers
   • XML::Parser
   • Stream-Based Versus Tree-Based Processing
   • Putting Parsers to Work
   • XML::LibXML
   • XML::XPath
   • Document Validation
   • XML::Writer
   • Character Sets and Encodings
7. Event Streams
8. • Working with Streams
   • Events and Handlers
   • The Parser as Commodity
   • Stream Applications
   • XML::PYX
   • XML::Parser
9. SAX
10. • SAX Event Handlers
    • DTD Handlers
    • External Entity Resolution
    • Drivers for Non-XML Sources
    • A Handler Base Class
    • XML::Handler::YAWriter as a Base Handler Class
    • XML::SAX: The Second Generation
11. Tree Processing
12. • XML Trees
    • XML::Simple
    • XML::Parser's Tree Mode
    • XML::SimpleObject
    • XML::TreeBuilder
    • XML::Grove
13. DOM
14. • DOM and Perl
    • DOM Class Interface Reference
    • XML::DOM
    • XML::LibXML
15. Beyond Trees: XPath, XSLT, and More
16. • Tree Climbers
    • XPath
    • XSLT
    • Optimized Tree Processing
17. RSS, SOAP, and Other XML Applications
18. • XML Modules
    • XML::RSS
    • XML Programming Tools
    • SOAP::Lite
19. Coding Strategies
20. • Perl and XML Namespaces
    • Subclassing
    • Converting XML to HTML with XSLT
    • A Comics Index

Index

You may also want to check out Erik T. Ray's home page, Jason McIntosh's home page, or O'Reilly's page for the book. You can purchase Perl &amp XML from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

Comments

My Biased Opinion...

[FortKnox]

I think that if you are making a large enough (enterprise?) website that requires a serious amount of XML development, you should ditch perl altogether and write it in Java. Java already handles XML efficiently, and is a better choice for large apps.

If you are writing a smaller website that uses XML, sure, perl is a nice choice. But is the XML necessary?

And I have used (and still use) both perl and Java. I just view Java as a better choice for large web apps, and perl for small web apps and scripting.

Before I get hit with flames, please understand this is my opinion, not fact.