XML::Compile::Translate(3)

NAME
XML::Compile::Translate - create an XML data parser

INHERITANCE
 XML::Compile::Translate is extended by
   XML::Compile::Translate::Reader
   XML::Compile::Translate::Template
   XML::Compile::Translate::Writer

SYNOPSIS
 # for internal use only
 my $code = XML::Compile::Translate->compile(...);

DESCRIPTION
This module converts a schema type definition into a code reference which can be used to interpret a schema. The sole public function in this package is compile(), and is called by XML::Compile::Schema::compile(), which does a lot of set-ups. Please do not try to use this package directly!

The code in this package interprets schemas; it understands, for instance, how complexType definitions work. Then, when the schema syntax is decoded, it will knot the pieces together into one CODE reference which can be used in the main user program.

  Unsupported features
This implementation is work in progress, but by far most structures in W3C schemas are implemented (and tested!).

Missing are
 schema noNamespaceSchemaLocation
 any ##local
 anyAttribute ##local

Some things do not work in schemas anyway: "import", "include". They only work if everyone always has a working connection to internet. You have to require them manually. Include also does work, because it does not use namespaces. (see XML::Compile::Schema::importDefinitions())

Ignored, because not for our purpose is the search optimization information: "key, unique, keyref, selector, field", and de schema documentation: "notation, annotation". Compile the schema schema itself to interpret the message if you need them.

A few nuts are still to crack:
 openContent
 facets on dates and base64Binary
 final is not protected

Of course, the latter list is all fixed in next release ;-) See chapter "DETAILS" for more on how the tune the translator.

METHODS

  Constructors

$obj->new($translator, %options)
    The %options are described in XML::Compile::Schema::compile(). Those descriptions will probably move here, eventually.

     -Option--Default
      nss     <required>

    nss => XML::Compile::Schema::NameSpaces

$obj->register($name)
XML::Compile::Translate->register($name)
    Register a new back-end.

    example:

     use XML::Compile::Translate::SomeBackend;
     XML::Compile::Translate::SomeBackend->register('SomeNAME');
     my $coderef = $schemas->compile('SomeNAME' => ...);

  Attributes

  Handlers

XML::Compile::Translate->compile($element|$attribute|$type, %options)
    Do not call this function yourself, but use XML::Compile::Schema::compile() (or wrappers around that).

    This function returns a CODE reference, which can translate between Perl datastructures and XML, based on a schema. Before this method is called is the schema already translated into a table of types.

DETAILS

  Translator options
performance optimization

The XML::Compile::Schema::compile() method (and wrappers) defines a set options to improve performance or usability. These options are translated into the executed code: compile time, not run-time!

The following options with their implications:

sloppy_integers BOOLEAN
    The "integer" type, as defined by the schema built-in specification, accepts really huge values. Also the derived types, like "nonNegativeInteger" can contain much larger values than Perl's internal "long". Therefore, the module will start to use Math::BigInt for these types if needed.

    However, in most cases, people design "integer" where an "int" suffices. The use of big-int values comes with heigh performance costs. Set this option to "true" when you are sure that ALL USES of "integer" in the scheme will fit into signed longs (are between -2147483648 and 2147483647 inclusive)

    If you do not want limit the number-space, you can safely add
      use Math::BigInt try => 'GMP' to the top of your main program, and install Math::BigInt::GMP. Then, a C library will do the work, much faster than the Perl implementation.

sloppy_floats BOOLEAN
    The float types of XML are all quite big, and may be NaN, INF, and -INF. Perl's normal floats do not, and therefore Math::BigFloat is used. This, however, is slow.

    When this option is true, your application will crash on any value which is not understood by Perl's internal float implementation... but run much faster.

check_values BOOLEAN
    Check the validity of the values, before parsing them. This will report errors for the reader, instead of crashes. The writer will not produce invalid data.

check_occurs BOOLEAN
    Checking whether the number of occurrences for an item are between "minOccurs" and "maxOccurs" (implied for "all", "sequence", and "choice" or explicitly specified) takes time. Of course, in cases errors must be handled. When this option is set to "false", only distinction between single and array elements is made.

ignore_facets BOOLEAN
    Facets limit field content in the restriction block of a simpleType. When this option is "true", no checks are performed on the values. In some cases, this may cause problems: especially with whiteSpace and digits of floats. However, you may be able to control this yourself. In most cases, luck even plays a part in this. Less checks means a better performance.

    Simple type restrictions are not implemented by other XML perl modules. When the schema is nicely detailed, this will give extra security.

validation BOOLEAN
    When used, it overrules the above "check_values", "check_occurs", and "ignore_facets" options. A true value enables all checks, a false value will disable them all. Of course, the latter is the fastest but also less secure: your program will need to validate the values in some other way.

    XML::LibXML has its own validate method, but I have not yet seen any performance figures on that. If you use it, however, it is of course a good idea to turn XML::Compile's validation off.

qualified XML

The produced XML may not use the name-spaces as defined by the schemas, just to simplify the input and output. The structural definition of the schemas is still in-tact, but name-space collission may appear.

Per schema, it can be specified whether the elements and attributes defined in-there need to be used qualified (with prefix) or not. This can cause horrible output when within an unqualified schema elements are used from another schema which is qualified.

The suggested solution in articles about the subject is to provide people with both a schema which is qualified as one which is not. Perl is known to be blunt in its approach: we simply define a flag which can force one of both on all schemas together, using "elements_qualified" and "attributes_qualified". May people and applications do not understand name-spaces sufficiently, and these options may make your day!

Name-spaces

The translator does respect name-spaces, but not all senders and receivers of XML are name-space capable. Therefore, you have some options to interfere.

prefixes HASH|ARRAY-of-PAIRS
    The translator will create XML elements (WRITER) which use name-spaces, based on its own name-space/prefix mapping administration. This is needed because the XML tree is created bottom-up, where XML::LibXML namespace management can only handle this top-down.

    When your pass your own HASH as argument, you can explicitly specify the prefixes you like to be used for which name-space. Found name-spaces will be added to the HASH, as well the use count. When a new name-space URI is discovered, an attempt is made to use the prefix as found in the schema. Prefix collisions are actively avoided: when two URIs want the same prefix, a sequence number is added to one of them which makes it unique.

    The HASH structure looks like this:

      my %namespaces =
        ( myns => { uri => 'myns', prefix => 'mypref', used => 1}
        , ...  => { uri => ... }
        );

      my $make = $schema->compile
        ( WRITER => ...
        , prefixes => \%namespaces
        );

      # share the same namespace defs with another component
      my $other = $schema->compile
        ( WRITER => ...
        , prefixes => \%namespaces
        );

    When used is specified and larger than 0, then the namespace will appear in the top-level output element (unless "include_namespaces" is false).

    Initializing using an ARRAY is a little simpler:

     prefixes => [ mypref => 'myns', ... => ... ];

    However, be warned that this does not work well with a false value for "include_namespaces": detected namespaces are added to an internal HASH now, which is not returned; that information is lost. You will need to know each used namespace beforehand.

include_namespaces BOOLEAN|CODE
    When true and WRITER, the top level returned XML element will contain the prefix definitions. Only name-spaces which are actually used will be included (a count is kept by the translator). It may very well list name-spaces which are not in the actual output because the fields which require them are not included for there is not value for those fields.

    If you like to combine XML output from separate translated parts (for instance in case of generating SOAP), you may want to delay the inclusion of name-spaces until a higher level of the XML hierarchy which is produced later.

    When a CODE reference is passed, it will be called for each used namespace, with the uri and prefix as parameters. Only when the CODE returns true, the namespace declaration will be included.

    When the compilation produces an attribute, then this option cannot be used.

namespace_reset BOOLEAN
    You can pass the same HASH to a next call to a reader or writer to get consistent name-space usage. However, when "include_namespaces" is used, you may get ghost name-space listings. This option will reset the counts on all defined name-spaces.

use_default_namespace BOOLEAN (added in release 0.57)
    When a true value, the blank prefix will be used for the first namespace URI which requires a auto-generated prefix. However, in quite some environments, people mix horrible non-namespace qualified elements with nice namespace qualified elements. In such situations, namespace the qualified-but-default prefix (i.e., no prefix) is confusing. Therefore, the option defaults to false: do not use the invisible prefix.

    You may explicitly specify a blank prefix with "prefixes", which will be used when applicable.

block_namespace NAMESPACE|TYPE|HASH|CODE|ARRAY
    [1.06] Available on global scale via XML::Compile::Schema::new(block_namespace) or XML::Compile::Schema::blockNamespace(), and for a single compiled instance via XML::Compile::Schema::compile(block_namespace).

    Some schemas include other schemas which you do not need. For instance, the other schema is only used in rare cases, or the other schema defines deprecated types and elements. Of course, you can simply not load those schemas... however: the main schema may refer to those types and elements you do not need. So, with this option, you can make the compilation to ignore whole namespaces and specific elements or types.

    The NAMESPACE is a uri, which will disable use of any element or type defined in that space. You may also provide a specific full $type (toplevel element or type name). You may also give an LIST or ARRAY of these, but then a HASH is much more suitable: with linear lookup time.

    When you provide a CODE reference, it will be called for each type and element to be judged. Passed are $type, $ns, $local, and $path. The "$ns/$local" is the decomposition of $type. When the CODE returns "undef", then it is undecisive, letting other rules decide. When it returns 0, then the thing will not be blocked (whatever the other rules decide). In other cases, the thing will not be used.

      # block a whole namespace
      $schema->blockNamespace("http://xyz.example.com");

      # block only a single element or typedef
      $schema->blockNamespace("{http://xyz.example.com}buggy");

      # block $ns1 and $type1, unblock $ns2
      $schema->blockNamespace( {$ns1 => 1, $ns2 => 0, $type1 => 1} );

      $schema->blockNamespace($ns1, $type1);
      $schema->compile(..., block_namespace => [$ns1, $type1]);
      $schema->new(..., block_namespace => [$ns1, $type1]);

      # very flexible
      sub want_block($$$$) ( my ($type,$ns,$local,$path) = @_; undef}
      $schema->blockNamespace(\&want_block);

    It is very well possible that the blocking of some namespaces breaks the validness of messages: when those elements are required but set to be ignored. There is no way to detect this, on the moment.

Wildcards handlers

Wildcards are a serious complication: the "any" and "anyAttribute" entities do not describe exactly what can be found, which seriously hinders the quality of validation and the preparation of XML::Compile. Therefore, if you use them then you need to process that parts of XML yourself. See the various backends on how to create or process these elements.

Automatic decoding is problematic: you do not know what to expect, so cannot prepare for these data-structures compile-time. However, XML::Compile::Cache offers a way out: you can declare the handlers for these "any" components and therewith be prepared for them. With XML::Compile::Cache::new(allow_undeclared), you can permit run-time compilation of the found components.

any_element CODE|'TAKE_ALL'|'SKIP_ALL'
    [0.89] This will be called when the type definition contains an "any" definition, after processing the other element components. By default, all "any" specifications will be ignored.

any_attribute CODE|'TAKE_ALL'|'SKIP_ALL'
    [0.89] This will be called when the type definitions contains an "anyAttribute" definition, after processing the other attributes. By default, all "anyAttribute" specifications will be ignored.

any_type CODE
    [1.07] Called for processing an "xsd:anyType" element. Currently only supported for the reader. By default, it returns a string when the element does not contains sub-elements, otherwise the XML node.

SEE ALSO
This module is part of XML-Compile distribution version 1.63, built on July 02, 2019. Website: http://perl.overmeer.net/xml-compile/

LICENSE
Copyrights 2006-2019 by [Mark Overmeer <markov@cpan.org>]. 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 http://dev.perl.org/licenses/