Ubuntu Manpage: XML::Compile::Translate - create an XML data parser

Provided by: libxml-compile-perl_1.63-3_all

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.

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/