ThinkGenealogy

Previous posts have explored a better way to cite online sources (Part 1), how citation information can be stored as a file using GEDCOM format (Part 2) and MARC format (Part 3). This post takes the next logical step and discusses MARC XML.

MARC was created as a machine-readable format many decades ago. In the last decade, eXtensible Markup Language (XML) has been developed as a standard format to allow validation, processing, and transformation of data. MARC XML takes the MARC format and represents it as XML. This is done in a lossless way so that conversions between MARC and MARC XML will not lose any data.

A book represented as a Source List Entry in Evidence Explained looks like this:

Geary, Edward A. A History of Emery County. Salt Lake City: Utah State Historical Society, 1996.

That same book listed with the Library of Congress is shown here as MARC XML.

Let’s quickly compare the MARC entries for author, title, and publication with the corresponding representation in MARC XML.

MARC

100 1#
  $a Geary, Edward A.,
245 12
  $a A history of Emery County.
260 ##
  $a Salt Lake City :
  $b Utah State Historical Society ;
  $c 1996.


MARC XML

  <datafield tag="100" ind1="1" ind2=" ">
    <subfield code="a">Geary, Edward A.,</subfield>
  </datafield>
  <datafield tag="245" ind1="1" ind2="2">
    <subfield code="a">A history of Emery County.</subfield>
  </datafield>
  <datafield tag="260" ind1=" " ind2=" ">
    <subfield code="a">Salt Lake City :</subfield>
    <subfield code="b">Utah State Historical Society ;</subfield>
    <subfield code="c">1996.</subfield>
  </datafield>


The three fields (author, title, publication) are each represented by a datafield element with corresponding tag and indicators (ind1, ind2).  The only difference being in my reformatting of MARC, indicator spaces were represented by the # sign.  Instead of the $ delimiter for subfields, each datafield element has a separate subfield element with the appropriate code letter.

The MARC XML representation is easier to read by a person (software developer) than the raw MARC file and is more easily processed due to most programming languages’ ability to work with XML.  XML is more descriptive and therefore file sizes would be larger for MARC XML than for MARC.  But the size is not likely to be an issue.

Because MARC XML is just a rendering of MARC into XML, the observations and questions from Part 3 apply.

MARC XML could also be a possible format to represent online source citation information.