Stephen Downes

This is a summary of The metadata enigma, by Ganesan Shankaranarayanan and Adir Even.

Metadata is thought of as a system's data dictionary, capturing definitions of data entities and the relationships among them. But it is much more than this. It is a complex description of data. Here are six types of metadata:

• Infrastructure metadata, which the components of the system
• Model metadata, or the data dictionary
• Process metadata, describing on how the data is generated
• Quality metadata, the assessment of the actual data
• Interface metadata, describing how users consume the data
• Administration metadata, which tracks data usage

It is worth contrast this description with the three types of metadata I describe in Resource Profiles:

First party metadata - production of the resource
- bibliographic metadata
- technical metadata
- rights metadata

Second party metadata - use of the resource
- sequencing and relational metadata
- interaction metadata

Third party metadata - about the resource
- classification metadata
- evaluative metadata
- educational metadata

Continuing with the summary:

When we think of how metadata is used, it is usually for things like search. As the author comments, "Metadata is likely to be useful in rational, data-driven, analytical decision-making scenarios." But what is not clear, he notes, is "whether it provides similar benefit in decision processes that are more intuitive or politically charged."

Various products exist to support metadata. But there are some industry-wide problems:

• Process and quality metadata are not well supported
• Little support for business metadata
• The use of relational or complex proprietary structures
• Metadata elements tightly coupled with one product or vendor

Design challenges that will become more significant in the future include:

• Interchangeable metadata formats
• Metadata exchange and integration - "The market, however, is still split between two competing metadata exchange standards: the Open Integration Model (OIM) and the Common Warehouse Model (CWM). The Metadata Coalition, led by Microsoft, proposed OIM in 1999. At about the same time, the Object Management Group, led by Oracle, promoted CWM."
• Design paradigms - "An elementary choice is from among the top-down, bottom-up, and hybrid strategies"
• Metadata quality

Is metadata worth the effort? The anser is not clear, because the benefits of metadata have not been clearnly established.

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