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'Metadata Rules' - a report from the Open Forum on Metadata Registries
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Top level
Web Services Papers
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Author: Alan Kotok
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Publishing date: 24.02.2003 12:15
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Alan Kotok reports from the recently held sixth annual Open Forum on Metadata Registries, where participants could evaluate various methods and options for representing metadata.
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To share data successfully, companies and individuals need to start somewhere, and for many parties looking to exchange data that "somewhere" is a registry. Registries provide an index or description of the information held or maintained by an organization or community of interest, and the data used for indexing or description are called metadata, literally defined as data about data. The role of registries in Web services and related technologies attracted a good deal of attention at a recent industry meeting devoted to the subject.
The sixth annual Open Forum on Metadata Registries held 20-24 January 2003 in Santa Fe, New Mexico (http://metadata-stds.org/OpenForum2003/) explored the role of registries and reported on new developments and applications. While not a large event (about 120 participants, many of which were speakers in the various sessions), the forum offered one of the few venues where participants could focus on registries, and evaluate various methods and options for representing metadata. But like so much in the Web services world, the need for various registries to work together was a continuing and critical topic heard at the event.
The University of California's Lawrence Berkeley Laboratory put on the forum, which attracted participants largely from government, academe, and the scientific community. Bruce Bargmeyer of Lawrence Berkeley National Laboratory organized and chaired the event, and set the tone early by calling for greater cooperation and interoperation among the various types of registries. Bargmeyer said the various registries could either need to consolidate - he showed a cartoon of big fish eating smaller fish in a form of registry food chain - or learn to work together.
Working together would not be easy, however. While registries often contain common content, Bargmeyer conceded that the issue is not as simple as it may look. The data may be common but they are often represented in different ways, which makes it all the more important for metadata to map across these different representations. He said the success of this effort will depend on how the community of registries manages the semantics of the metadata. Bargmeyer's statement prompted a forum participant to shout, "Metadata rules!"
Value of registries Registries provide a good starting point for data sharing because they offer an authoritative place to find resources for exchanging or reusing data with business partners or colleagues, either inside or outside an organization, including the rules for data sharing and descriptions of the kinds of data shared. The objects referenced in a registry can include entire standards or specifications, components of the standards or specifications, XML schemas or schema components, software components, data elements, database structures, or related documentation, such as guidelines or best practices, depending on the task at hand.
Registries can likewise offer information about the parties exchanging data themselves. Organizations can use registries to list basic identification or location data, information about the products or services the organizations offer, their technical capabilities, and requirements for doing business such as message formats and security levels.
Registries have great potential value because they offer a common method for representing the characteristics about the registered objects - e.g., organizations, specifications, schemas, components, elements represented by common metadata. By devising standards for registries and their metadata, especially those accessible over the Web, designers can build registries into an overall architecture for exchanging data within or among organizations. Standards also enable registries to interact with each other, thus encouraging a distributed environment, which in turn encourages individual registries to become smaller, easier to develop, and easier to maintain.
The Standards Landscape The first two days of the event featured introductions to and tutorials on different registry methods and standards:
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Metadata registries defined by ISO standard 11179
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Registries for software components and developments
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Universal Description, Discovery and Integration (UDDI) registries
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Electronic Business XML (ebXML) registries
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SQL database catalogs
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Dublin Core registries of information resources
Understanding the operation and features of the various registries was an important part of the conference and a foundation on which to discuss consolidation and co-operation.
ISO 11179 Much of the event featured presentations about ISO 11179 - officially ISO/IEC 11179, Specification and Standardization of Data Elements - a metadata standard with 10 years of experience and one with an extensive paper trail. The forum featured an introductory presentation the first day and a day-long tutorial on the second day. ISO11179 is an international standard for data elements, defining one of the basic building blocks in the development of knowledge. The standard covers the composition, classification, naming, identification, and registration of data elements, and over its history has contributed to many other technical and business standards.
As described by Larry Fitzwater of the U.S. Environmental Protection Agency (EPA) and one of the standard committee leaders, ISO 11179 is divided into six major sections:
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Framework
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Labels all the parts of the standard, which helps accurately understand metadata and their use in a registry
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Classification
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Helps derive and formulate abstract and application data elements. This section reduces ambiguity by recognizing the relationships among data element concepts and data elements themselves.
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Basic attributes
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Offers a basic set of attributes to describe a data element. It also specifies a metamodel for the registration of metadata. This part encourages comparison across systems and facilitates information exchange, two key features of interoperability. Fitzwater called this section "the essential part of 11179."
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Definitions
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Provides rules and guidelines for defining terms. Fitzwater noted (and many will agree) good definitions are not easy to write, and consistent definitions encourage sharing of data.
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Naming, identification
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Offers naming conventions, which like the definitions section, provide a consistent method for identifying and assembling data elements.
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Registration
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Outlines steps in the registration data elements, and describes the role and responsibilities of a registration authority. Fitzwater said an ISO work group is rewriting this section, adding more specificity.
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The naming conventions in section 5 of ISO 11179 have been adopted by other standards efforts (e.g. ebXML core components, X12 reference model for XML design). Section 5 also provides guidance on creating unique identifiers for data elements, using both a straight string as the basic name, with context added to help make the name understandable.
Fitzwater noted that the newer e-business registry standards and specifications, such as UDDI and ebXML, deal with different kinds of objects and interactions. But because of ISO 11179's longevity and experience with metadata and registries, it offers lessons for registry federation and interoperability from which the newer initiatives can benefit.
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