A proposed perl data structure for storing marc info


$record is a hash reference

$record->{leader}=
$record->{bibid}=58973
$record->{tags}=$tags

$tags is a hash reference

$tags->{$tag}
$tags->{$tag}->{$tagorder}
$tags->{$tag}->{$tagorder}->{indicator}='04'
$tags->{$tag}->{$tagorder}->{tagid}=573498
$tags->{$tag}->{$tagorder}->{subfields}=$subfields

$subfields is a hash reference

$subfields->{$mark}
$subfields->{$mark}->{$subfieldorder}
$subfields->{$mark}->{$subfieldorder}='MacDonald, John A.'

Sample :
bibid=58973,
110 ## $afirst text $asecond text $bthird text
120 ## $alast text ??
120 01 $nno, another text

in perlmarcstructure, it can be writen :
$record->{bibid}=58973;
$record->{tags}->{110}->{1}->{indicator}='##';
$record->{tags}->{110}->{1}->{subfields}->{a}->{1}='first text';
$record->{tags}->{110}->{1}->{subfields}->{a}->{2}='second text';
$record->{tags}->{110}->{1}->{subfields}->{b}->{1}='third text';

$record->{tags}->{120}->{1}->{indicator}='##';
$record->{tags}->{120}->{1}->{subfields}->{a}->{1}='last text ??';

$record->{tags}->{120}->{2}->{indicator}='01';
$record->{tags}->{120}->{2}->{subfields}->{n}->{1}='no, another text';

This takes care of possible repeating tags and subfields as well as ordering of
tags and subfields, but it makes it difficult to look up specific tags and
subfields without looping through every time.  It might be an idea to add an
index to the structure to aid these lookups.

$record->{index}->{110}->{tags}=\(3,4)   <-- array ref shows that tags 3 and 4
					     are 110 tags

Need a similar index for subfields.... I'm not sure if this is any simpler than
just looping through the tags every time.  :)

I think looping is the way to go...

This still needs more work.  This will also require an API for accessing or
modifying this structure, as it is non-trivial to parse the data.  I'm also
starting to wonder how difficult it is going to be to develop templates using
this kind of structure.  HTML::Template has no facility for parsing this kind
of data structure.  We might need an alternate (or completely different) data
structure that is parseable by HTML::Template.