NAME

XML::DT - a package for down translation of XML files

SYNOPSIS

use XML::DT;

%xml=( 'music'    => sub{"Music from: $c\n"},
       'lyrics'   => sub{"Lyrics from: $v{name}\n"},
       'title'    => sub{ uc($c) },
       '-default' => sub{"$q:$c"} );

print dt($filename,%xml);

ABSTRACT

This module is a XML down processor. It maps tag (element) names to functions to process that element and respective contents.

DESCRIPTION

This module processes XML files with an approach similar to OMNIMARK. As XML parser it uses XML::Parser or XML::LibXML module in an independent way. At configure stage, you should choose one of the back-ends.

If you use XML::LibXML module as backend, you can parse HTML files as if they were XML files. For this, you must supply an extra option to the hash:

%hander = ( -html => 1,
            ...
          );

Functions

dt

Down translation function dt receives a filename and a set of expressions (functions) defining the processing and associated values for each element.

dtstring

dtstring works in a similar way with dt but takes input from a string instead of a file.

dturl

dturl works in a similar way with dt but takes input from an Internet url instead of a file.

pathdt

The pathdt function is a dt function which can handle a subset of XPath on handler keys. Example:

%handler = (
  "article/title"        => sub{ toxml("h1",{},$c) },
  "section/title"        => sub{ toxml("h2",{},$c) },
  "title"                => sub{ $c },
  "//image[@type='jpg']" => sub{ "JPEG: <img src=\"$c\">" },
  "//image[@type='bmp']" => sub{ "BMP: sorry, no bitmaps on the web" },
)

pathdt($filename,%handler);

Here are some examples of valid XPath expressions under XML::DT:

/aaa
/aaa/bbb
//ccc                           - ccc somewhere (same as "ccc")
/*/aaa/*
//*                             - same as "-default"
/aaa[@id]                       - aaa with an attribute id
/*[@*]                          - root with an attribute
/aaa[not(@name)]                - aaa with no attribute "name"
//bbb[@name='foo']              - ... attribute "name" = "foo"
/ccc[normalize-space(@name)='bbb']
//*[name()='bbb']               - complex way of saying "//bbb"
//*[starts-with(name(),'aa')]   - an element named "aa.*"
//*[contains(name(),'c')]       - an element       ".*c.*"
//aaa[string-length(name())=4]                     "...."
//aaa[string-length(name())<4]                  ".{1,4}"
//aaa[string-length(name())>5]                  ".{5,}"

Note that not all XPath is currently handled by XML::DT. A lot of XPath will never be added to XML::DT because is not in accordance with the down translation model. For more documentation about XPath check the specification at http://www.w3c.org or some tutorials under http://www.zvon.org

pathdtstring

Like the dtstring function but supporting XPath.

pathdturl

Like the dturl function but supporting XPath.

inctxt

inctxt(pattern) is true if the actual element path matches the provided pattern. This function is meant to be used in the element functions in order to achieve context dependent processing.

ctxt

Returns the context element of the currently being processed element. So, if you call ctxt(1) you will get your father element, and so on.

toxml

This is the default "-default" function. It can be used to generate XML based on $c $q and %v variables. Example: add a new attribute to element ele1 without changing it:

%handler=( ...
  ele1 => sub { $v{at1} = "v1"; toxml(); },
)

toxml can also be used with 3 arguments: tag, attributes and contents

toxml("a",{href=> "http://local/f.html"}, "example")

returns:

<a href='http://local/f.html'>example</a>

xmltree

This simple function just makes a HASH reference:

{ -c => $c, -q => $q, all_the_other_attributes }

The function toxml understands this structure and makes XML with it.

mkdtskel

Used by the mkdtskel script to generate automatically a XML::DT perl script file based on an XML file. Check mkdtskel for details.

mkdtdskel

Used by the mkdtskel script to generate automatically a XML::DT perl script file based on a DTD file. Check mkdtdskel for details.

Accessing parents

With XML::DT you can access an element parent (or grand-parent) attributes, till the root of the XML document.

If you use c<$dtattributes[1]{foo} = 'bar'> on a processing function, you are defining the attribute foo for that element parent.

In the same way, you can use $dtattributes[2] to access the grand-parent. $dtattributes[-1] is, as expected, the XML document root element.

User provided element processing functions

The user must provide an HASH with a function for each element, that computes element output. Functions can use the element name $q, the element content $c and the attribute values hash %v.

All those global variables are defined in $CALLER::.

Each time an element is find the associated function is called.

Content is calculated by concatenation of element contents strings and interior elements return values.

-default function

When a element has no associated function, the function associated with -default called. If no -default function is defined the default function returns a XML like string for the element.

When you use /-type definitions, you often need do set -default function to return just the contents: sub{$id}.

-outputenc option

-outputenc defines the output encoding (default is Unicode UTF8).

-inputenc option

-inputenc forces a input encoding type. Whenever that is possible, define the input encoding in the XML file:

<?xml version='1.0' encoding='ISO-8859-1'?>

-pcdata function

-pcdata function is used to define transformation over the contents. Typically this function should look at context (see inctxt function)

The default -pcdata function is the identity

-begin function

Function to be executed before processing XML file.

Example of use: initialization of side-effect variables

-end function

Function to be executed after processing XML file. I can use $c content value. The value returned by -end will be the dt return value.

Example of use: post-processing of returned contents

Elements with values other than strings (-type)

By default all elements return strings, and contents ($c) is the concatenation of the strings returned by the sub-elements.

In some situations the XML text contains values that are better processed as a structured type.

The following types (functors) are available:

ID

returns the contents. Very similar to <sub{$c}>

STR

concatenates all the sub-elements returned values (DEFAULT) all the sub-element should return strings to be concatenated;

SEQ

makes an ARRAY with all the sub elements contents; attributes are ignored (they should be processed in the sub-element). (returns a ref) If you have different types of sub-elements, you should use SEQH

SEQH

makes an ARRAY of HASH with all the sub elements (returns a ref); for each sub-element:

-q  => element name
-c  => contents
at1 => at value1    for each attribute

MAP

makes an HASH with the sub elements; keys are the sub-element names, values are their contents. Attributes are ignored. (they should be processed in the sub-element) (returns a ref)

MULTIMAP

makes an HASH of ARRAY; keys are the sub-element names; values are lists of contents; attributes are ignored (they should be processed in the sub-element); (returns a ref)

MMAPON(element-list)

makes an HASH with the sub-elements; keys are the sub-element names, values are their contents; attributes are ignored (they should be processed in the sub-element); for all the elements contained in the element-list, it is created an ARRAY with their contents. (returns a ref)

XML

return a reference to an HASH with:

-q  => element name
-c  => contents
at1 => at value1    for each attribute

ZERO

don't process the sub-elements; return ""

When you use /-type definitions, you often need do set -default function returning just the contents sub{$id}.

An example:

 use XML::DT;
 %handler = ( contacts => sub{ [ split(";",$c)] },
              -default => sub{$c},
	      -type    => { institution => 'MAP',
	                    degrees     =>  MMAPON('name')
		            tels        => 'SEQ' }
            );
 $a = dt ("f.xml", %handler);

with the following f.xml

<degrees>
   <institution>
      <id>U.M.</id>
      <name>University of Minho</name>
      <tels>
         <item>1111</item>
         <item>1112</item>
         <item>1113</item>
      </tels>
      <where>Portugal</where>
      <contacts>J.Joao; J.Rocha; J.Ramalho</contacts>
   </institution>
   <name>Computer science</name>
   <name>Informatica </name>
   <name> history </name>
</degrees>

would make $a

 { 'name' => [ 'Computer science',
               'Informatica ',
	       ' history ' ],
   'institution' => { 'tels' => [ 1111, 1112, 1113 ],
  	              'name' => 'University of Minho',
	              'where' => 'Portugal',
	              'id' => 'U.M.',
	              'contacts' => [ 'J.Joao',
			       ' J.Rocha',
			       ' J.Ramalho' ] } };

DT Skeleton generation

It is possible to build an initial processor program based on an example

To do this use the function mkdtskel(filename).

Example:

perl -MXML::DT -e 'mkdtskel "f.xml"' > f.pl

DTD skeleton generation

It makes a naive DTD based on an example(s).

To do this use the function mkdtdskel(filename*).

Example:

perl -MXML::DT -e 'mkdtdskel "f.xml"' > f.dtd

SEE ALSO

mkdtskel(1) and mkdtdskel(1)

AUTHORS

Home for XML::DT;

http://natura.di.uminho.pt/~jj/perl/XML/

Jose Joao Almeida, <jj@di.uminho.pt>

Alberto Manuel Simões, <albie@alfarrabio.di.uminho.pt>

thanks to

Michel Rodriguez <mrodrigu@ieee.org> José Carlos Ramalho <jcr@di.uminho.pt> Mark A. Hillebrand

cpanm XML::DT

perl -MCPAN -e shell
install XML::DT