=head1 NAME

XML::Compile - Compilation based XML processing

=head1 INHERITANCE

 XML::Compile is extended by
   XML::Compile::Schema

=head1 SYNOPSIS

 # See XML::Compile::Schema / ::WSDL / ::SOAP

=head1 DESCRIPTION

Many (professional) applications process XML messages based on a formal
specification, expressed in XML Schemas.  XML::Compile translates
between XML and Perl with the help of such schemas.  Your Perl program
only handles a tree of nested HASHes and ARRAYs, and does not need to
understand namespaces and other general XML and schema nastiness.

Three serious WARNINGS:

=over 4

=item *

The focus is on B<data-centric XML>, which means that mixed elements
are not handler automatically: you need to work with XML::LibXML nodes
yourself, on these spots.

=item *

The B<data is not strictly validated>, still a large number of
compile-time errors can be reported.  Values are checked quite thoroughly.
Structure as well.

=item *

Imports and includes, as used in the schemas, are NOT performed
automaticly.  Schema's and such are NOT collected from internet
dynamically; you have to call L<XML::Compile::Schema::importDefinitions()|XML::Compile::Schema/"Administration">
explictly with filenames of locally stored copies. Includes do only
work if they have a targetNamespace defined, which is the same as that
of the schema it is included into.

=back

For end-users, the following packages are of interest (the other
are support packages):

=over 4

=item L<XML::Compile::Schema|XML::Compile::Schema>

Interpret schema elements and types: create processors for XML messages.

=item L<XML::Compile::SOAP|XML::Compile::SOAP>

Use the SOAP protocol, client side.

=item L<XML::Compile::WSDL11|XML::Compile::WSDL11>

Use SOAP with a WSDL version 1.1 communication specification file.

=item L<XML::Compile::SOAP::Daemon|XML::Compile::SOAP::Daemon>

Create a SOAP daemon, directly from a WSDL file.

=item L<XML::Compile::Tester|XML::Compile::Tester>

Helps you write regression tests.

=item L<XML::Compile::Cache|XML::Compile::Cache>

Helps you administer compiled readers and writers, especially useful it
there are a lot of them.  Extends L<XML::Compile::Schema|XML::Compile::Schema>.

=item L<XML::Rewrite|XML::Rewrite>

Clean-up XML structures: beautify, simplify, extract.

=item L<XML::Compile::Dumper|XML::Compile::Dumper>

Enables you to save pre-compiled XML handlers, the results of any
C<compileClient>.  However, this results in huge files, so this may
not be worth the effort.

=back

=head1 METHODS

Methods found in this manual page are shared by the end-user modules,
and should not be used directly: objects of type C<XML::Compile> do not
exist!

=head2 Constructors

These constructors are base class methods to be extended,
and therefore should not be accessed directly.

=over 4

=item XML::Compile-E<gt>B<new>([XMLDATA], OPTIONS)

The XMLDATA is a source of XML. See L<dataToXML()|XML::Compile/"Compilers"> for valid ways,
for example as filename, string or C<undef>.

If you have compiled all readers and writers you need, you may simply
terminate the compiler object: that will clean-up (most of) the
XML::LibXML objects.

 -Option        --Default
  parser_options  <many>
  schema_dirs     undef

=over 2

=item parser_options => HASH|ARRAY

See XML::LibXML::Parser for a list of available options which can be
used to create an XML parser (the new method). The default will set you
in a secure mode.  See L<initParser()|XML::Compile/"Compilers">.

=item schema_dirs => DIRECTORY|ARRAY-OF-DIRECTORIES

Where to find schema's.  This can be specified with the
environment variable C<SCHEMA_DIRECTORIES> or with this option.
See L<addSchemaDirs()|XML::Compile/"Accessors"> for a detailed explanation.

=back

=back

=head2 Accessors

=over 4

=item $obj-E<gt>B<addSchemaDirs>(DIRECTORIES|FILENAME)

=item XML::Compile-E<gt>B<addSchemaDirs>(DIRECTORIES|FILENAME)

Each time this method is called, the specified DIRECTORIES will be added
in front of the list of already known schema directories.  Initially,
the value of the environment variable C<SCHEMA_DIRECTORIES> is added
(therefore tried as last resort). The constructor option C<schema_dirs>
is a little more favorite.

Values which are C<undef> are skipped.  ARRAYs are flattened.  Arguments
are split at colons (on UNIX) or semi-colons (windows) after flattening.
The list of directories is returned, in all but VOID context.

When a C<.pm> package FILENAME is given, then the directory
to be used is calculated from it (platform independently).  So,
C<something/XML/Compile.pm> becomes C<something/XML/Compile/xsd/>.
This way, modules can simply add their definitions via C<<
XML::Compile->addSchemaDirs(__FILE__) >> in a BEGIN block or in main.
ExtUtils::MakeMaker will install everything what is found in the
C<lib/> tree, so also your xsd files.  Probably, you also want to use
L<knownNamespace()|XML::Compile/"Administration">.

example: adding xsd's from your own distribution

  # file xxxxx/lib/My/Package.pm
  package My::Package;

  use XML::Compile;
  XML::Compile->addSchemaDirs(__FILE__);
  # now xxxxx/lib/My/Package/xsd/ is also in the search path

  use constant MYNS => 'http://my-namespace-uri';
  XML::Compile->knownNamespace(&MYNS => 'my-schema-file.xsd');
  $schemas->importDefinitions(MYNS);

=back

=head2 Compilers

=over 4

=item $obj-E<gt>B<dataToXML>(NODE|REF-XML-STRING|XML-STRING|FILENAME|FILEHANDLE|KNOWN)

=item XML::Compile-E<gt>B<dataToXML>(NODE|REF-XML-STRING|XML-STRING|FILENAME|FILEHANDLE|KNOWN)

Collect XML data, from a wide variety of sources.  In SCALAR context,
an XML::LibXML::Element or XML::LibXML::Document is returned.
In LIST context, pairs of additional information follow the scalar result.

When a ready XML::LibXML::Node (::Element or ::Document) NODE is
provided, it is returned immediately and unchanged.  A SCALAR reference is
interpreted as reference to XML as plain text (XML texts can be large,
and you can improve performance by passing it around by reference
instead of copy).  Any value which starts with blanks followed by a
'E<lt>' is interpreted as XML text.

You may also specify a pre-defined I<known> name-space URI.  A set of
definition files is included in the distribution, and installed somewhere
when this all gets installed.  Either define an environment variable
named SCHEMA_LOCATION or use L<new(schema_dirs)|XML::Compile/"Constructors"> (option available to
all end-user objects) to inform the library where to find these files.

According the XML::LibXML::Parser manual page, passing a FILEHANDLE
is much slower than pasing a FILENAME.  However, it may be needed to
open a file with an explicit character-set.

example: 

  my $xml = $schema->dataToXML('/etc/config.xml');
  my ($xml, %details) = $schema->dataToXML($something);

  my $xml = XML::Compile->dataToXML('/etc/config.xml');

=item $obj-E<gt>B<initParser>(OPTIONS)

=item XML::Compile-E<gt>B<initParser>(OPTIONS)

Create a new parser, an XML::LibXML::Parser object. By default, the
parsing is set in a safe mode, avoiding exploits. You may explicitly
overrule it, especially if you need to process entities.

=back

=head2 Administration

=over 4

=item $obj-E<gt>B<findSchemaFile>(FILENAME)

=item XML::Compile-E<gt>B<findSchemaFile>(FILENAME)

Runs through all defined schema directories (see L<addSchemaDirs()|XML::Compile/"Accessors">)
in search of the specified FILENAME.  When the FILENAME is absolute,
that will be used, and no search is needed.  An C<undef> is returned when
the file is not found, otherwise a full path to the file is returned to
the caller.

Although the file may be found, it still could be unreadible.

=item $obj-E<gt>B<knownNamespace>(NAMESPACE|PAIRS)

=item XML::Compile-E<gt>B<knownNamespace>(NAMESPACE|PAIRS)

If used with only one NAMESPACE, it returns the filename in the
distribution (not the full path) which contains the definition.

When PAIRS of NAMESPACE-FILENAME are given, then those get defined.
This is typically called during the initiation of modules, like
L<XML::Compile::WSDL11|XML::Compile::WSDL11> and L<XML::Compile::SOAP|XML::Compile::SOAP>.  The definitions
are global: not related to specific instances.

The FILENAMES are relative to the directories as specified with some
L<addSchemaDirs()|XML::Compile/"Accessors"> call.

=item $obj-E<gt>B<walkTree>(NODE, CODE)

Walks the whole tree from NODE downwards, calling the CODE reference
for each NODE found.  When that routine returns false, the child
nodes will be skipped.

=back

=head1 DETAILS

=head2 Comparison

Where other Perl modules (like SOAP::WSDL) help you using these schemas
(often with a lot of run-time [XPath] searches), XML::Compile takes a
different approach: instead of run-time processing of the specification,
it will first compile the expected structure into a pure Perl CODE
reference, and then use that to process the data as often as needed.

There are many Perl modules with the same intention as this one:
translate between XML and nested hashes.  However, there are a few
serious differences:  because the schema is used here (and not by the
other modules), we can validate the data.  XML requires validation but
quite a number of modules simply ignore that.

Next to this, data-types are formatted and processed correctly; for
instance, the specification prescribes that the C<Integer> data-type
must accept values of at least 18 digits... not just Perl's idea of longs.

XML::Compile supports the more complex data-types like C<list>, C<union>,
C<substitutionGroup> (unions on complex type level), and even the
nasty C<any> and C<anyAttribute>, which is rarely the case for the
other modules.

=head1 SEE ALSO

This module is part of XML-Compile distribution version 1.29,
built on October 16, 2012. Website: F<http://perl.overmeer.net/xml-compile/>

Other distributions in this suite:
L<XML::Compile>,
L<XML::Compile::SOAP>,
L<XML::Compile::SOAP12>,
L<XML::Compile::SOAP::Daemon>,
L<XML::Compile::SOAP::WSA>,
L<XML::Compile::C14N>,
L<XML::Compile::WSS>,
L<XML::Compile::Tester>,
L<XML::Compile::Cache>,
L<XML::Compile::Dumper>,
L<XML::Compile::RPC>,
L<XML::Rewrite>,
L<XML::eXistDB>,
and
L<XML::LibXML::Simple>.

Please post questions or ideas to the mailinglist at
F<http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/xml-compile>
For live contact with other developers, visit the C<#xml-compile> channel
on C<irc.perl.org>.

=head1 LICENSE

Copyrights 2006-2012 by [Mark Overmeer]. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See F<http://www.perl.com/perl/misc/Artistic.html>

