Object representation of the metadata element.
   Object fields are:
    Scalar:     metadataIdRef, 
    Scalar:     id, 
    Object reference:   subject => type ARRAY,
    Object reference:   parameters => type ARRAY,
    Object reference:   eventType => type ,
    Object reference:   key => type HASH,

   The constructor accepts only single parameter, it could be a hashref to parameters hash  or DOM with  'metadata' element 

    

              use perfSONAR_PS::Datatypes::v2_0::nmwg::Message::Metadata;

          my $el =  perfSONAR_PS::Datatypes::v2_0::nmwg::Message::Metadata->new($DOM_Obj);

      creates   object, accepts DOM with  element tree or hashref to the list of
      keyd parameters
         metadataIdRef   => undef, 
         id   => undef, 
         subject => ARRAY,
         parameters => ARRAY,
         key => HASH,

       accept parent DOM
       return metadata object DOM, generated from object contents 

    if any of subelements can be an arrray then this method will provide
    facility to add another element to the  array and will return ref to such array
    or just set the element to a new one
=cut

sub addSubject { my $self = shift; my $new = shift; my $logger = get_logger( $CLASSPATH );

    $self->subject && ref($self->subject) eq 'ARRAY'?push @{$self->subject}, $new:$self->subject([$new]); 
    $logger->debug("Added new to subject"); 
    $self->buildIdMap; ## rebuild index map 
    $self->buildRefIdMap; ## rebuild ref index map  
    return $self->subject;
}

     remove specific element from the array of subject elements by id ( if id is supported by this element )
     accepts single param - id - which is id attribute of the element
     if there is no array then it will return undef and warninig
     if it removed some id then $id will be returned

     get specific element from the array of subject elements by id ( if id is supported by this element )
     accepts single param - id
     if there is no array then it will return just an object

    if any of subelements can be an arrray then this method will provide
    facility to add another element to the  array and will return ref to such array
    or just set the element to a new one
=cut

sub addParameters { my $self = shift; my $new = shift; my $logger = get_logger( $CLASSPATH );

    $self->parameters && ref($self->parameters) eq 'ARRAY'?push @{$self->parameters}, $new:$self->parameters([$new]); 
    $logger->debug("Added new to parameters"); 
    $self->buildIdMap; ## rebuild index map 
    $self->buildRefIdMap; ## rebuild ref index map  
    return $self->parameters;
}

     remove specific element from the array of parameters elements by id ( if id is supported by this element )
     accepts single param - id - which is id attribute of the element
     if there is no array then it will return undef and warninig
     if it removed some id then $id will be returned

     get specific element from the array of parameters elements by id ( if id is supported by this element )
     accepts single param - id
     if there is no array then it will return just an object

      depending on config  it will return some hash ref  to the initialized fields
    for example querySQL ()
    accepts one optional prameter - query hashref
    will return:
    { ip_name_src =>  'hepnrc1.hep.net' },}

      merge with another metadata ( append + overwrite if exists )
      we can do it differently
      method #1:
         convert to dom both objects and then get resulted object from combined dom 
      method #2 default:
         through the introspection of the object

    if any of subelements has id then get a map of it in form of
    hashref to { element}{id} = index in array and store in the idmap field

   will parse all subelements and register all namepspaces within the metadata namespace

   Maxim Grigoriev (FNAL)  2007-2008, maxim@fnal.gov