Page 118 - Building Digital Libraries

General-Purpose Technologies Useful for Digital Repositories

{“c”:”280”}]}},
{“500”:{“ind1”:”\\,”
“ind2”:”\\,”
“subfields”:[{“a”:”Description derived from published bibliography.”}]}},
{“520”:{“ind1”:”\\,”
“ind2”:”\\,”
“subfields”:[{“a”:”Detailed township map showing drainage, cities and towns, county and township
boundaries, roads, and railroads.”}]}},
{“500”:{“ind1”:”\\,”
“ind2”:”\\,”
“subfields”:[{“a”:”County population in upper left.”}]}},
{“530”:{“ind1”:”\\,”
“ind2”:”\\,”
“subfields”:[{“a”:”Available also through the Library of Congress Web site as a raster
image.”}]}},
{“650”:{“ind1”:”\\,”
“ind2”:”0,”
“subfields”:[{“a”:”Railroads”},
{“z”:”Ohio”},
{“v”:”Maps.”}]}},
{“752”:{“ind1”:”\\,”
“ind2”:”\\,”
“subfields”:[{“a”:”United States”},
{“b”:”Ohio.”}]}},
{“852”:{“ind1”:”0,”
“ind2”:”\\,”
“subfields”:[{“a”:”Library of Congress”},
{“b”:”Geography and Map Division”},
{“e”:”Washington, D.C. 20540–4650 USA”},
{“n”:”dcu”}]}},
{“856”:{“ind1”:”4,”
“ind2”:”1,”
“subfields”:[{“d”:”g4081p”},
{“f”:”rr002800”},
{“u”:”http:\/\/hdl.loc.gov\/loc.gmd\/g4081p.rr002800”},
{“q”:”c”}]}}]}

Again, the data above is well structured, but when consumed by a browser
or a language as a JSON file, the elements within the field become actionable
objects. Unlike the XML document, which would require decisions related
to processing type, technologies, and so on, loading this record into a JSON
parser would immediately allow the developer to process the data as a set of
objects, an array of objects, or as a hash. For example, I would easily count
the number of times a field appeared by simply asking a count of the object:
json_object[“856”].count. This changes the relationship that developers are
able to have with the data, and adds a level of richness that XML simply
doesn’t provide when interacting with the information as a programmer.
So, what does this mean for digital libraries? If you are a metadata cre-
ator or an individual exporting metadata to share with another organization
or individual, it is very likely that you will only be working with XML data,
and technologies like XSLT or XQuery will be the primary method that will
be used to process the information. For this use case, XML’s portability and
ability to embed the schema documents within the XML data packet are
extremely valuable because they give other individuals the ability to validate

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