Marc Chantreux > marc-mir-0.3 > lib/MARC/MIR.pod

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MIR: MARC Intermediate Representation ^

MARC::MIR is not a library, it's a specification for in-memory representation of a MARC record with simplcity in mind. The current module comes with a set of helpers to manipulate it (i call it MARC::MIR DSL).

The DSL itself is designed to be used the more natural way possible. Here are some basic exemples (combined with Perlude).

    use Modern::Perl;
    use MARC::MIR;
    use Perlude;

    # marcdump

    now {say for_humans from_iso2709} iso2709_records_of 'source.mrc'

    # report the IDs of the 10 first records of the file

    now {
        any_fields {
            tag eq '001' and say value
        } from_iso2709
    } take 10, iso2709_records_of 'echantillon_ecparis.raw';

    # or 

    now {
        $_ = from_iso2709;
        any_fields {
            tag eq '001' and say value
        }
    } take 10, iso2709_records_of 'echantillon_ecparis.raw';

Some other modules and documentations are worth to read.

MARC::MIR::Template

(shipped appart) is a description format to import/export a MIR from/to a datastructures that fit modern formats like JSON or XML.

MARC::MIR::Tutorial

gives basic exemples of use of the MARC::MIR DSL described below.

WARNINGS ^

t/* is empty and the API may change (i even i think it's quiet stable on the basics). i think the doc is up to date and the stability of MARC::MIR.

Anyway: waiting for the tests, MARC::MIR runs daily on linux stations (perl 5.12 to 5.17) on large amount of data. It is as faster and easier to use than older libraries and is designed to get the data back from iso files, no matter the quality of the serialization dictionnary so for one shot scripts, i'm now more confident in MARC::MIR than i ever was in MARC::Record, for example.

MOTIVATION ^

I dealt with lot of MARC records in the past (mainly from/to iso2709 files) and was really annoyed by the state of art:

ISO2709 was a clever format when it was invented (more than 40 years ago! older than FTP or even UNIX) but the world has changed a so drastic way most of the IT crowd, bred to modern serialization formats (YAML, JSON, XML) are clueless when it comes to magnetic tapes friendly serializations. Librarians haven't got it since recently.

As a result, IT people just flee libraries and reinvent information sciences from scratch with modern tools fitting the modern interconnected world when librarians are left with the rest of us, dead bored programmers using old school tools and bad designed modules with painfull OO approach. I don't blame anyone: it's just the way the things gone.

But if you come back to the roots: A MARC record is a very simple structure so they must be simple to manulate. MARC::MIR is an attempt to get the simplicity back.

SPECIFICATION ^

so MIR is just an array of array (see man perllol) with very simple rules:

    record       = [ header, [fields] ]
    fields       = controlfield | datafield
    controlfield = [tag,string]
    datafield    = [tag,[subfields],indicators]
    indicators   = [ ind1, ind2 ] # can be represented as a 2 chars fields
    subfields    = [tag,string]

note that tags are always at the index 0, data always at 1.

All the indexes that are not used by the spec can be used to store instructions for middleware and serializer purposes. there is no convention there.

Examples

A MIR control field is a tag and a value.

    [ '001', '1231313145' ]

A MIR data field

    [ $tag, [@subfield] ]
    [ $tag, [@subfield], "  " ]
    [ $tag, [@subfield], [' ',' '] ]

A MIR record

    [ '01972cam0a2200541   450' => 
        [ [ '001' => '2344564564' ] # this is the ID
        ,   [ '856'
            , [ [ q => "jpeg" ]
              , [ z => "cover from original version" ] 
              , [ u => "http://localhost/img/" ] 
              ]
            ]
        ]
    ]

DSL ^

the use of $_ and thd (_) prototype is idiomatic: almost every subs are written to be used a very natural way (my hope is librians to write some code). So we prefer to write

    say for_humans from_iso2709

than a more pythonic way

    say( for_humans( from_iso2709( $_ )))

map_*, with_*, any_*, grep_*

# TODO: maybe an array there ?

tag, value, indicators

ISO2709 handling

# TODO: from|to_iso2709

CIB handling

# TODO: from|to_iso2709

Authors ^

    * Marc Chantreux (eiro) marcc(at)cpan.org
    * You? https://github.com/eiro/p5-marc-mir

KNOWN BUGS ^

feedbacks are very welcome. the only known bugs are

     * with_fields needs $_
     * map_datafields can't work 
     * *_values? must crash on references
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