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Yaz and Metaproxy

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Kirk Hess edited this page Mar 24, 2017 · 3 revisions

Dependencies

Yaz

The retrieval tool in YAZ is driven by an XML configuration, documented in the YAZ User's Guide and Reference.

Yaz can be installed from a package manager and the basic method for running a static conversion is using rdf-lookup

Static Conversion

The retrieval tool in YAZ is driven by an XML configuration, documented in the YAZ User's Guide and Reference. The YAZ conversion for RDF/XML is called rdf-lookup, and the static configuration looks like this:

<backend syntax="xml" name="rdf-lookup">
  <xslt stylesheet="xsl/marc2bibframe2.xsl"/>
  </rdf-lookup>
</backend>

With this configuration saved as record-conv.xml, you could perform an active conversion of a MARCXML file using the yaz-record-conv utility:

yaz-record-conv record-conv.xml test/data/marc.xml

Active conversion

Active conversion of records - resolving URIs for elements of the RDF/XML output from authoritative sources, like the Library of Congress Name Authority File, is achieved through a retrieval tool conversion in the YAZ toolkit.

The retrieval tool in YAZ is driven by an XML configuration, documented in the YAZ User's Guide and Reference. The YAZ conversion for RDF/XML is called rdf-lookup, and the configuration looks like this:

<backend syntax="xml" name="rdf-lookup">
  <xslt stylesheet="xsl/marc2bibframe2.xsl"/>
  <rdf-lookup debug=1>
    <namespace prefix="bf" href="http://id.loc.gov/ontologies/bibframe/" />
    <namespace prefix="bflc" href="http://id.loc.gov/ontologies/bflc/"/>
    <lookup xpath="//bf:contribution/bf:Contribution/bf:agent/bf:Agent">
      <key field="bflc:name00MatchKey"/>
      <key field="bflc:name01MatchKey"/>
      <key field="bflc:name11MatchKey"/>
      <server url="http://id.loc.gov/authorities/names/label/%s" method="HEAD"/>
    </lookup>
  </rdf-lookup>
</backend>

From the YAZ User's Guide:

The debug=1 attribute tells the filter to add XML comments to the key nodes that indicate what lookup it tried to do, how it went, and how long it took. The namespace prefix bf: is defined in the namespace tags. These namespaces are used in the xpath expressions in the lookup sections. The lookup tag specifies one tag to be looked up. The xpath attribute defines which node to modify. It may make use of the namespace definitions above. The server tag gives the URL to be used for the lookup. A %s in the string will get replaced by the key value. If there is no server tag, the one from the preceding lookup section is used, and if there is no previous section, the id.loc.gov address is used as a default. The default is to make a GET request, this example uses HEAD.

With this configuration saved as record-conv.xml, you could perform an active conversion of a MARCXML file using the yaz-record-conv utility:

yaz-record-conv record-conv.xml test/data/marc.xml

The rdf-lookup conversion support was first introduced in YAZ v5.19.0. YAZ 5.20.0 provided a significant performance improvement for HEAD requests, so using that version or higher is highly recommended.

Metaproxy integration

Both the static and active conversions can be easily integrated into Index Data's Metaproxy metasearch gateway software as a record output format. A sample filter configuration is in the metaproxy directory. With this filter configuration, an SRU request to the server like http://metaproxy.mylibrary.org/?version=1.1&operation=searchRetrieve&query=rec.id%3D13600108&recordSchema=bibframe2&startRecord=1&maximumRecords=1 would retrieve and display the requested record converted into BIBFRAME triples in RDF/XML format. The install-filters.sh script in that directory would deploy the filters into a running Metaproxy configuration.

In addition, we have provided a Vagrantfile and Ansible playbook to build a local Metaproxy VM using VirtualBox for testing, available in the deploy directory.

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