use Bio::Biblio::IO;
  my $io = new Bio::Biblio::IO (-format => 'pubmedxml');

     # set the version for version checking
    $VERSION = do { my @r = (q$$Revision: 1.4 $ =~ /\d+/g); sprintf "%d.%-02d", @r };
    $Revision = q$$Id: pubmedxml.pm,v 1.4 2002/10/22 07:45:13 lapp Exp $;

    my ($self, @args) = @_;
    
    # make a hashtable from @args
    my %param = @args;
    @param { map { lc $_ } keys %param } = values %param; # lowercase keys

    # copy all @args into this object (overwriting what may already be
    # there) - changing '-key' into '_key', and making keys lowercase
    my $new_key;
    foreach my $key (keys %param) {
	($new_key = $key) =~ s/^-/_/;
	$self->{ lc $new_key } = $param { $key };
    }

    # find the format for output - and put it into a global $Convert
    # because it will be used by the event handler who knows nothing
    # about this object
    my $result = $self->{'_result'} || 'pubmed2ref';
    $result = "\L$result";	# normalize capitalization to lower case

    # a special case is 'raw' when no converting module is loaded
    # and citations will be returned as a hashtable (the one which
    # is created during parsing XML file/stream)
    unless ($result eq 'raw') {

	# load module with output converter - as defined in $result
	if (defined &Bio::Biblio::IO::_load_format_module ($result)) {
	    $Bio::Biblio::IO::medlinexml::Convert = "Bio::Biblio::IO::$result"->new (@args);
	}
    }

    # create an instance of the XML parser
    # (unless it is already there...)
    $self->{'_xml_parser'} = new XML::Parser (Handlers => {Init  =>\& Bio::Biblio::IO::medlinexml::handle_doc_start,
							   Start =>\& handle_start,
							   End   =>\& handle_end,
							   Char  =>\& Bio::Biblio::IO::medlinexml::handle_char,
							   Final =>\& Bio::Biblio::IO::medlinexml::handle_doc_end})
	unless $self->{'_xml_parser'};

    # if there is an argument '-callback' then start parsing at once -
    # the registered event handlers will use 'callback' to report
    # back after each citation
    #
    # we need to remember this situation also in a global variable
    # because the event handler subroutines know nothing about this
    # object (unfortunately)
    if ($SUPER::Callback = $self->{'_callback'}) {
	$self->_parse;
    }
}

# ---------------------------------------------------------------------
#
#   Here are the event handlers (they do the real job!)
#
# Note that these methods do not know anything about the object they
# are part of - they are called as subroutines. not as methods.
# It also means that they need to use global variables to store and
# exchnage intermediate results.
#
# ---------------------------------------------------------------------

#
# This is a list of #PCDATA elements.
#
%PCDATA_NAMES =
    (
     'PublicationStatus' => 1,
     'ProviderId' => 1,
     'ArticleId' => 1,
     'URL' => 1,
     );

%SIMPLE_TREATMENT =
    (
     'History' => 1,
     'PubMedArticle' => 1,
     'PubmedArticle' => 1,
     'PubmedData' => 1,
     );

%POP_DATA_AND_PEEK_OBJ =
    (
     'Year' => 1,
     'Month' => 1,
     'Day' => 1,
     'Hour' => 1,
     'Minute' => 1,
     'Second' => 1,
     'ProviderId' => 1,
     'PublicationStatus' => 1,
     );

%POP_AND_ADD_DATA_ELEMENT =
    (
     'PubMedPubDate' => 'pubDates',
     'History' => 'histories',
     );

    my ($expat, $e) = @_;

    #
    # First I have to deal with those elements which are both PCDATA
    # (and therefore they are on the pcdataStack) and which have an
    # attribute list (therefore they are also known as a separate
    # p-object on the objectStack.
    #
    if ($e eq 'ArticleId') {
	&Bio::Biblio::IO::medlinexml::_data2obj ('id');
	&Bio::Biblio::IO::medlinexml::_add_element ('pubmedArticleIds', pop @Bio::Biblio::IO::medlinexml::ObjectStack);
#	&Bio::Biblio::IO::medlinexml::_debug_object_stack ("END", $e);
	return;
    }

    if ($e eq 'URL') {
	&Bio::Biblio::IO::medlinexml::_data2obj ('URL');
	&Bio::Biblio::IO::medlinexml::_add_element ('pubmedURLs', pop @Bio::Biblio::IO::medlinexml::ObjectStack);
#	&Bio::Biblio::IO::medlinexml::_debug_object_stack ("END", $e);
	return;
    }


    #
    # both object and pcdata stacks elements mixed here together
    #

    if (exists $POP_DATA_AND_PEEK_OBJ{$e}) {
	&Bio::Biblio::IO::medlinexml::_data2obj ("\l$e");

    } elsif (exists $POP_AND_ADD_DATA_ELEMENT{$e}) {
	&Bio::Biblio::IO::medlinexml::_add_element ($POP_AND_ADD_DATA_ELEMENT{$e}, pop @Bio::Biblio::IO::medlinexml::ObjectStack);

    } elsif ($e eq 'MedlineCitation' ||
	     $e eq 'NCBIArticle') {
	&Bio::Biblio::IO::medlinexml::_obj2obj ('Citation');

    } elsif ($e eq 'PubmedData') {
	&Bio::Biblio::IO::medlinexml::_obj2obj ('PubmedData');

    } elsif ($e eq 'PubMedArticle' ||
	     $e eq 'PubmedArticle') {

	#
	# Here we finally have the whole citation ready.
	#
	&Bio::Biblio::IO::medlinexml::_process_citation (pop @Bio::Biblio::IO::medlinexml::ObjectStack);

    } else {
	&Bio::Biblio::IO::medlinexml::handle_end ($expat, $e);	
    }
    
#    &Bio::Biblio::IO::medlinexml::_debug_object_stack ("END", $e);

}

1;
__END__

    my ($expat, $e, %attrs) = @_; 
#    &Bio::Biblio::IO::medlinexml::_debug_object_stack ("START", $e);

    #
    # The #PCDATA elements which have an attribute list must
    # be first here - because for them I create entries both on
    # the @PCDataStack _and_ on @ObjectStack.
    #
    if ($e eq 'ArticleId') {
	my %p = ();
	$p{'idType'} = (defined $attrs{'IdType'} ? $attrs{'IdType'} : 'pubmed');
	push (@Bio::Biblio::IO::medlinexml::ObjectStack,\% p);
    }

    if ($e eq 'URL') {
	my %p = ();
	$p{'type'} = $attrs{'type'} if $attrs{'type'};
	$p{'lang'} = $attrs{'lang'} if $attrs{'lang'};
	push (@Bio::Biblio::IO::medlinexml::ObjectStack,\% p);
    }

    #
    # Then we have #PCDATA elements without an attribute list.
    # For them I create an entry on @PCDataStack.
    #
    if (exists $PCDATA_NAMES{$e}) {
	push (@Bio::Biblio::IO::medlinexml::PCDataStack, '');

    #
    # And finally, all non-PCDATA elements go to the objectStack
    #
    } elsif (exists $SIMPLE_TREATMENT{$e}) {
	push (@Bio::Biblio::IO::medlinexml::ObjectStack, {});

    } elsif ($e eq 'ArticleIdList') {
	;

    } elsif ($e eq 'PubMedPubDate') {
	my %p = ();
	$p{'pubStatus'} = $attrs{'PubStatus'} if $attrs{'PubStatus'};
	push (@Bio::Biblio::IO::medlinexml::ObjectStack,\% p);

    } else {
	&Bio::Biblio::IO::medlinexml::handle_start ($expat, $e, %attrs);	
    }

  bioperl-l@bioperl.org              - General discussion
  http://bioperl.org/MailList.shtml  - About the mailing lists

  bioperl-bugs@bioperl.org
  http://bugzilla.bioperl.org/

 Usage   : print $Bio::Biblio::IO::pubmedxml::VERSION;
           print $Bio::Biblio::IO::pubmedxml::Revision;