Understanding XFML - eXchangeable Faceted Metadata Language XML Format

XFML is an eXchangeable Faceted Metadata Language for sharing and publishing hierarchical metadata. This is much helpful in searching documents and to reduce the work that is done in indexing the data available. This is easy to implement and very powerful. This is an open XML format. Any XFML document should conform to the XFML core specification. Details about the core XFML can be found in the link http://purl.oclc.org/NET/xfml/core/

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XFML core is being built as a subset of XML Topic Maps. Hence XFML will be compatible with topicmaps. Any XFML file can be converted to a valid XTM easily with less effort. XFML has faceted classification of data and it enables hierarchical classification and indexing data. This enables data to be inter-related. The basic building block of XFML is topic. All the topics come under some facet. To under stand facet clearly look at the classification of data given below in hierarchical form:

· AAA University
o Electrical
§ Basics of Electrical
§ Basics of Electronics
o Electronics
§ Basics of Electrical
§ Basics of Electronics
· BBB University
o Electrical
§ Basics of Electrical
§ Basics of Electronics
o Electronics
§ Basics of Electrical
§ Basics of Electronics

In the above classification of data the universities can be in the category of “Places to Study”. Hence “Places to Study” is a facet. The other facets for the above data can be “Specialization” and “SubjectName”. The code given below would be the main content of the XFML document for the data given above:

<facet id="PlaceToStudy">University</facet>
<facet id="Specialization">Specialization</facet>
<facet id="SubjectName">Subject Name</facet>
<topic id="AAA University" facetid="PlaceToStudy">
<name>AAA University</name></topic>
<topic id="BBB University" facetid="PlaceToStudy">
<name>BBB University</name></topic>
<topic id="Electrical" facetid="Specialization">
<name>Electrical</name></topic>
<topic id="Electronics" facetid="Specialization">
<name>Electronics</name></topic>
<topic id="Basics of Electrical" facetid="SubjectName">
<name>Basics of Electrical</name></topic>
<topic id="Basics of Electronics" facetid="SubjectName">
<name>Basics of Electronics</name></topic>

An XFML document should start with the declaration XML and then the XFML as given below:

<?xml version="1.0" ?>
<xfml version="1.0" url="http://yoursite.com/pathto/file.xml" language="en-us">

The XFML document would end with the closing tag of XFML as </xfml>.

Facets and topics are the building blocks of any XFML document. Facets would not have any child elements but topics can have any number of child elements. The number of topics for a particular facet id can be any number.

You can index some web pages and add them to your XFML document using the <page> tag. An example of the page tag would be something like given below:

<page url="http://www.someurl.com/">
<title>Some Title for the url.</title>
<description>content description for the url given.</description>
<occurrence topicid="AAA University" />
<occurrence topicid="Electrical" />
<occurrence topicid="Basic Electronics" />
</page>

The <page> tag would have the link to the web page in the url attribute. A child element of the <page> called the <occurrence> has the topicid attribute which gives the value of the topic id that is referenced in the url given.

There is another tag called the <mapInfo> in the XFML document. This tag is used to given information on the administrative contacts. The common tags that are found in the <mapInfo> tage are the name, email, url, and license tags.

For reusing indexes, you need to connect the topics to other maps. This is done by the <connect> tag which is a child element of the <topic> element. The <connect> tag would have the url of the map to which that particular topic is to be connected. An example of the connect tag would be:

<topic id="Basics of Electronics" facetid="SubjectName">
<name>Basics of Electronics</name>
<connect> http://yoursite.com/pathto/file2.xml#Electrical
</connect>
</topic>

The other way to reuse indexes is to point the topic to some other published resources on the web. This way of pointing to other resources on the web can be done using the <psi> tags. PSI stands for the Published Subject Indicator. The <psi> tag is used as given below:

<topic id="Basics of Electronics" facetid="SubjectName">
<name>Basics of Electronics</name>
<psi>http://www.somereferencesite.com/search?q=Electrical
</psi>
</topic>

Thus XFML an eXtensible Faceted Metadata Language that finds it use in creating a XML formatted document that is used for faceted classification of the metadata and for reusing the indexes already created by some other resource.

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