[MIMAS logo] MIMAS Metadatabase: Metadata Technical Details


Metadata Standards

The metadata records in the Metadatabase are standards-based, using Dublin Core and standard encoding schemes for appropriate fields.

Metadata Records

The metadata records in the Metadatabase are qualified Dublin Core, but with some MIMAS-specific extensions. They are encoded in XML according to a Document Type Definition, which is translated into XHTML for Web display. The Dublin Core metadata is mapped to Z39.50 attributes and result formats and to the software application indexes.

Because the MIMAS service consists of a heterogeneous collection of services and datasets across many disciplines, a common, cross-domain metadata schema is required for their description, hence the choice of qualified Dublin Core. Someone searching for information about for example 'economic' will be able to discover results of possible interest across many of the MIMAS services beyond the obvious macro-economic datasets, including JSTOR, census data, satellite images and bibliographic resources. In the future the metadata may be extended to include records according to domain-specific standards, but the MIMAS metadata cross searching capability would of necessity still be based on the 'core' metadata encoded in qualified Dublin Core.

Where possible the metadata conforms to standard qualified Dublin Core. But this is extended for some Dublin Core elements to enable the capture of information which is MIMAS-specific or according to schemes which are not currently endorsed by Dublin Core. These local additions to qualified Dublin Core effectively make up the MIMAS application profile for the metadatabase. The inclusion of UNESCO as a subject, type and spatial classification scheme described below is an example of local extensions, as is the capture of MIMAS-specific subjects and types. Some administrative metadata is included: the name of the person who created the metadata; the creation date; and the identifier of the record within the MIMAS Metadatabase. Capturing the name of the metadata creator will be of use for future quality checks and updating.

Standard Classification and Encoding Schemes

To provide quality metadata for discovery, subject keywords within the metadata are encoded according to standard classification or encoding schemes. In order to facilitate improved cross-domain searching by both humans and applications where choices of preferred subject scheme might vary, MIMAS Metadata provides subjects encoded according to several schemes. As well as the encoding schemes currently recognised within qualified Dublin Core, Library of Congress Subject Headings (LCSH) and Dewey Decimal, UNESCO subject keywords are also available. In addition, MIMAS-specific subjects are included to capture existing subject keywords on the MIMAS web site service information pages supplied by the content or application creators as well as MIMAS support staff. The use of standard classification schemes will improve resource discovery and will also assist in the provision of browsing structures for subject-based information gateways.

Similar classification schemes are included for 'Type' to better classify the type of the resource for cross-domain searching. Each metadata record includes a 'Type' from the high-level DCMI Type Vocabulary, 'Service' in the example above, but for some MIMAS records this will be 'Collection' or 'Dataset'. In addition, the above example includes type indications, including 'Bibliographical citations' and 'Online searching', according to standard schemes. Again the MIMAS-specific resource type is included, and this is used to structure the top level of the metadata hierarchy.

Countries covered by information within a MIMAS service are detailed according to their ISO3166 names and also their UNESCO names, captured within the 'dcterms:spatial' element of the metadata record and shown on the web display as 'Country'. This is of particular relevance to the macro-economic datasets, such as the IMF databanks, which include data from many countries in the world. Temporal coverage, again of relevance to the macro-economic datasets, is captured within a 'dcterms:temporal' element and encoded according to the W3CDTF scheme. This is displayed as 'Time' and may consist of several temporal ranges. Information about access requirements to a particular MIMAS service is recorded as free-text within a 'dc:rights' element and displayed as 'Access'.

The MIMAS Metadata Hierarchy

Although each of the records within the MIMAS Metadatabase is created, indexed and available for discovery individually, the records represent parts of the service within a hierarchy.

During metadata creation only the 'isPartOf' relation is recorded, as the MIMAS identifier of the parent metadata record. The 'hasPart' fields and the displayed titles and links for parent and child metadata records are included by the MIMAS Metadatabase application. Hard coding 'hasPart' fields into a metadata record would necessitate the inefficient process of updating a parent record whenever a new child record were added. Dynamic generation of these links assists in simplifying the metadata creation and update process, and in maintaining the consistency of the metadata.

A further navigation hierarchy is provided by the application. If a parent and a child record, according to the 'isPartOf' hierarchy, also have a matching MIMAS subject keyword, the application includes a link from the parent's subject keyword to the particular child record. Again this subject navigation hierarchy is provided dynamically by the application and does not depend on the accuracy of metadata creation beyond the 'isPartOf' identifier and the matching subject keyword.

The child, 'hasPart', links within the MIMAS metadata hierarchy are available in the web interface only. A metadata record retrieved through the Z39.50 interface will include a single 'isPartOf' relation at most, which will consist of the MIMAS identifier of the parent record. Any required linking between records would be provided by the application retrieving the records.

Data Details

The MIMAS Metadatabase project was funded by the Joint Information Systems Committee (JISC) for the UK Higher and Further Education Councils as part of the JISC Services DNER: Z39.50/Authentication Programme.

22 December 2003, epub@manchester.ac.uk          [Go to MIMAS home page]          [Valid XHTML 1.0!]