Perl and XML

Author: John M. Gabriele | back to index

Perl and XML

Quick notes on XML

Content of an XML file

Structure and tags

Commonly-used Perl modules

General use

Validating XML files against a W3C Schema

Validating XML files against a DTD

Finding elements in a tree

Transforming XML files into some other format

Links

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My quick reference notes on using Perl with XML.

Quick notes on XML

Tiny XML refersher.

Content of an XML file

Only one top-level element per file.

All elements have start/end tags, except ones that look like <this/> .
Quote your attribute values (either <with a='single'> <or b="double"> quote marks).
Use <, >, and & for <, >, and &. Also, use " and ' for undirected double-quote and single-quote marks.

Structure and tags

You specify the structure and tags of your XML files with either a DTD or a schema. DTD's came from SGML. Schema's are newer.

The Perl Cookbook tells me that the W3C standard (http://www.w3.org/TR/xmlschema-0/) "XML Schema" is the most common schema language but also is complex and problematic.

You usually use a schema or a DTD for validating an xml file against.

Use XML::Twig. Note, XML::Twig makes use of (actually, is a subclass of) the standard XML::Parser, which in turn talks to the expat C library. Don't directly use XML::Parser -- let wrappers like Twig talk to it for you.

Also, for just writing simple XML files, XML::Simple can be quite useful.

Validating XML files against a W3C Schema

Use XML::Xerces. (XML::LibXML can do this, but it's currently undocumented.) See also XML::Validator::Schema.

Validating XML files against a DTD

Use XML::LibXML (which uses Gnome's libxml2). See also XML::Checker.

Finding elements in a tree

See XML::XPath support in XML::LibXML.

Transforming XML files into some other format

See XML::LibXSLT (built on Gnome's libxslt library).