NAME
HTML::HTML5::Microdata::Parser - fairly experimental parser for HTML
'microdata'
SYNOPSIS
use HTML::HTML5::Microdata::Parser;
my $parser = HTML::HTML5::Microdata::Parser->new($html, $baseURI);
my $graph = $parser->graph;
DESCRIPTION
This package aims to have a roughly compatible API to RDF::RDFa::Parser.
Microdata is an experimental metadata format, not in wide use. Use this
module at your own risk.
$p = HTML::HTML5::Microdata::Parser->new($html, $baseuri, \%options,
$storage)
This method creates a new HTML::HTML5::Microdata::Parser object
and returns it.
The $xhtml variable may contain an XHTML/XML string, or a
XML::LibXML::Document. If a string, the document is parsed using
HTML::HTML5::Parser and HTML::HTML5::Sanity, which may throw an
exception. HTML::HTML5::Microdata::Parser does not catch the
exception.
The base URI is used to resolve relative URIs found in the
document.
Options [default in brackets]:
* alt_stylesheet - Magic rel="alternate stylesheet". [1]
* auto_config - See section "Auto Config" [0]
* mhe_lang - Process <meta http-equiv=Content-Language>.
[1]
* prefix_empty - URI prefix for itemprops of untyped items.
[undef]
* strategy - URI generation strategy for itemprops of
typed items. [HTML::HTML5::Microdata::
Strategy::Heuristic]
* tdb_service - thing-described-by.org when possible. [0]
* xhtml_base - Process <base href> element. [1]
* xhtml_lang - Process @lang. [1]
* xhtml_meta - Process <meta>. [0]
* xhtml_cite - Process @cite. [0]
* xhtml_rel - Process @rel. [0]
* xhtml_time - Process <time> element more nicely. [0]
* xhtml_title - Process <title> element. [0]
* xml_lang - Process @xml:lang. [1]
$storage is an RDF::Trine::Storage object. If undef, then a new
temporary store is created.
$p->xhtml
Returns the HTML source of the document being parsed.
$p->uri Returns the base URI of the document being parsed. This will
usually be the same as the base URI provided to the constructor,
but may differ if the document contains a <base> HTML element.
Optionally it may be passed a parameter - an absolute or
relative URI - in which case it returns the same URI which it
was passed as a parameter, but as an absolute URI, resolved
relative to the document's base URI.
This seems like two unrelated functions, but if you consider the
consequence of passing a relative URI consisting of a
zero-length string, it in fact makes sense.
$p->dom Returns the parsed XML::LibXML::Document.
$p->set_callbacks(\%callbacks)
Set callback functions for the parser to call on certain events.
These are only necessary if you want to do something especially
unusual.
$p->set_callbacks({
'pretriple_resource' => sub { ... } ,
'pretriple_literal' => sub { ... } ,
'ontriple' => undef ,
});
Either of the two pretriple callbacks can be set to the string
'print' instead of a coderef. This enables built-in callbacks
for printing Turtle to STDOUT.
For details of the callback functions, see the section
CALLBACKS. "set_callbacks" must be used *before* "consume".
"set_callbacks" itself returns a reference to the parser object
itself.
$p->consume
The document is parsed for Microdata. Nothing of interest is
returned by this function, but the triples extracted from the
document are passed to the callbacks as each one is found.
The "graph" method automatically calls "consume", so normally
you don't need to call it manually. If you're using callback
functions, it may be useful though.
$p->consume_microdata_item($element)
You almost certainly do not want to use this method.
It will consume a single Microdata item, assuming that $element
is an element that does or should have the @itemscope attribute
set. Returns the URI or blank node identifier for the item.
This method is exposed mostly for the benefit of
HTML::HTML5::Microdata::ToRDFa.
$p->graph()
This method will return an RDF::Trine::Model object with all
statements of the full graph.
$p->graphs()
Provided for RDF::RDFa::Parser compatibility.
CALLBACKS
Several callback functions are provided. These may be set using the
"set_callbacks" function, which taskes a hashref of keys pointing to
coderefs. The keys are named for the event to fire the callback on.
pretriple_resource
This is called when a triple has been found, but before preparing the
triple for adding to the model. It is only called for triples with a
non-literal object value.
The parameters passed to the callback function are:
* A reference to the "HTML::HTML5::Microdata::Parser" object
* A reference to the "XML::LibXML::Element" being parsed
* Subject URI or bnode (string)
* Predicate URI (string)
* Object URI or bnode (string)
The callback should return 1 to tell the parser to skip this triple (not
add it to the graph); return 0 otherwise.
pretriple_literal
This is the equivalent of pretriple_resource, but is only called for
triples with a literal object value.
The parameters passed to the callback function are:
* A reference to the "HTML::HTML5::Microdata::Parser" object
* A reference to the "XML::LibXML::Element" being parsed
* Subject URI or bnode (string)
* Predicate URI (string)
* Object literal (string)
* Datatype URI (string or undef)
* Language (string or undef)
Beware: sometimes both a datatype *and* a language will be passed. This
goes beyond the normal RDF data model.)
The callback should return 1 to tell the parser to skip this triple (not
add it to the graph); return 0 otherwise.
ontriple
This is called once a triple is ready to be added to the graph. (After
the pretriple callbacks.) The parameters passed to the callback function
are:
* A reference to the "HTML::HTML5::Microdata::Parser" object
* A reference to the "XML::LibXML::Element" being parsed
* An RDF::Trine::Statement object.
The callback should return 1 to tell the parser to skip this triple (not
add it to the graph); return 0 otherwise. The callback may modify the
RDF::Trine::Statement object.
ITEMPROP URI GENERATION STRATEGY
The "itemprop" attribute does not need to be a full URI.
<div itemscope itemtype="http://example.com/Person">
<span itemprop="phoneNumber">01234 567 890</span>
</div>
The "strategy" option passed to the constructor tells the parser how to
convert "phoneNumber" in the above example into a URI. This can be a
callback function, or an object or class that provides a "generate_uri"
method.
Three strategies are bundled with this distribution:
* HTML::HTML5::Microdata::Strategy::Basic - don't attempt to convert
to a URI
* HTML::HTML5::Microdata::Strategy::Heuristic - smart strategy, the
default
* HTML::HTML5::Microdata::Strategy::Microdata0 - official strategy of
early Microdata drafts
AUTO CONFIG
HTML::HTML5::Microdata::Parser has a lot of different options that can
be switched on and off. Sometimes it might be useful to allow the page
being parsed to control some of the options. If you switch on the
'auto_config' option, pages can do this.
A page can set options using a specially crafted <meta> tag:
<meta name="http://search.cpan.org/dist/HTML-HTML5-Microdata-Parser/#auto_config"
content="alt_stylesheet=0&prefix_empty=http://example.net/" />
Note that the "content" attribute is an
application/x-www-form-urlencoded string (which must then be
HTML-escaped of course). Semicolons may be used instead of ampersands,
as these tend to look nicer:
<meta name="http://search.cpan.org/dist/HTML-HTML5-Microdata-Parser/#auto_config"
content="alt_stylesheet=0;prefix_empty=http://example.net/" />
Any option allowed in the constructor may be given using auto config,
except 'auto_config' itself.
SEE ALSO
XML::LibXML, RDF::Trine, RDF::RDFa::Parser, HTML::HTML5::Parser,
HTML::HTML5::Sanity.
<http://www.perlrdf.org/>.
AUTHOR
Toby Inkster <tobyink@cpan.org>.
COPYRIGHT AND LICENCE
Copyright (C) 2009-2011 by Toby Inkster
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
DISCLAIMER OF WARRANTIES
THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.