C-1.2 Multiple Schemas Metadata Aggregation Model


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In this model there is a central aggregator, with no common metadata schema defined. Each of the content owners provides their metadata in their existing format together with their schema. Examples are RepUK, Go-Geo! and VADS (though for VADS the schemas are quite standardised for image collections). This is described in the following diagram:
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Figure C2: Multiple=
Figure C2: Multiple Schemas Metadata Aggregation Model
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One example of a service could be to create a standardised schema with associated metadata from a subset of the available schemas and metadata. This would enable those with more specific needs for metadata to develop a schema based on their needs, and convert the metadata into that standardised schema accordingly. This could be of particular use in relation to subject areas with significantly differing needs, considering for example the analysis of medical images, geological images and performance art films.
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The main advantages and disadvantages of this approach are summarised in the following table.
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Advantages Disadvantages
  • All collections are capable of providing their metadata in their own format: lower barrier to contribution.
  • No information is lost as all the information is shared; metadata is as complete as the source.
  • All the schemas and metadata are available: the end-user can evaluate the full metadata and determine whether it is fit for their purpose.
  • Others can manipulate the metadata, potentially enriching the metadata, for their own purposes.
  • Metadata is cached, making it available more quickly.
  • Potential services have a richer source of metadata available on which to build.
  • A simple record links to a richer catalogue record.
  • This is ‘messy behind the scenes’.
  • Comparison of items is not straightforward, as multiple schemas and technical knowledge are needed: there are ‘many standards [schemas] to search against’.
  • Updates to the source collection schemas may mean services using these need mapping or functional updates to ensure continuity of service.
  • Collections owners may not be able to merge enriched metadata back into their source metadata, due to the complexity of technical, financial or other constraints.
  • It becomes unmanageable if there are too many schemas.
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One participant thought that this model would become unmanageable if there were too many schemas in the aggregation, and considered that up to about six would be manageable. However, a number of the aggregators already using this model include more than six data sets, so this limit can be overcome.
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As this model would extend to holding metadata schemas and the associated data sets for other media, this would allow for users who would like to be able to see information about their areas in more detail. One example is a researcher, who wanted to see images and films about a subject, linked to the papers in which they had been used and the books and papers that were referenced in the paper. This approach has been nicknamed the ‘pick n mix’ approach, since those who want to use the metadata can aggregate the schemas they choose in any way they choose.

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