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Developing Metadata Standards

Developing Metadata Standards. Cleo Sgouropoulou email: csgouro @ cs.ntua . gr. Metadata Standards. The terms " metadata standard " or " metadata schema " are often used to refer to the various kinds of specifications for metadata available from different organizations.

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Developing Metadata Standards

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  1. Developing Metadata Standards Cleo Sgouropoulou email: csgouro@cs.ntua.gr

  2. Metadata Standards • The terms "metadata standard" or "metadata schema" are often used to refer to the various kinds of specifications for metadata available from different organizations. • Metadata standards come in different forms and with different kinds of audiences • Generic, framework-level models • The DCMI Abstract Model (DCAM), defining the underlying model for Dublin Core metadata terms • RDF, the Resource Description Framework, a general-purpose, web-oriented metadata framework, defined by the W3C.

  3. Metadata Standards • Generic, framework-level syntaxes • Expressions of Dublin Core in RDF/XML/XHTML, describing syntaxes for encoding DCAM-compatible metadata in various syntaxes • RDF/XML and other RDF syntaxes. • General-purpose element sets to be reused in many different contexts • DCMI Metadata Terms, defining a set of metadata terms conforming to the DCMI Abstract Model. • Domain-specific complete element sets and schemas • IEEE LOM Data Model, defining the basic metadata elements and how they combine into a LOM instance. IEEE LOM currently has an XML syntax only.

  4. A framework for MS

  5. Abstract Model Standards • Underlying most metadata specifications there is an assumption about an abstract model (referred to as "meta-model" or "data model"), within the framework of which the metadata is defined. • The abstract model specifies the concepts used in the standard, the nature of terms and how they combine to form a metadata description. • The abstract model is the schematics used by an application to understand a metadata expression given in a specific format, thus making it possible for a single standard, though expressed in several different formats, to still be understood in a uniform way by users and applications.

  6. Abstract Model Standards • IEEE LOM uses an abstract hierarchical model with no formal semantics. RDF, and as consequence, Dublin Core, use an entity-relationship model grounded in model-theoretical semantics • The models differ substantially in their methods for adding extensions • the XML-based models base their extensions on XML Schema • IEEE LOM depends on being able to extend the hierarchy • the entity-relationship-based models have no notion of "extensions" as there is no base set of elements to begin with.

  7. Abstract Model Standards

  8. Metadata Formats • Metadata exchange is performed using one of several metadata formats or bindings. • A binding is constructed by specifying how each kind of concept in the abstract model is to be encoded in a particular format (encoding). Also, a binding specifies how to interpret data given in a specific format in terms of the abstract model (interpretation)

  9. Metadata Formats

  10. Metadata Vocabularies • A vocabulary can be one of two things: • An element vocabulary, consisting of a set of metadata properties together with their definitions. For example, the Dublin Core Element Set, consisting of the 15 original Dublin Core elements (dc:title, dc:subject, etc.), is such a vocabulary. Used to construct application profiles, schemas and ontologies that describe how metadata instances are to be constructed • A value vocabulary, consisting of concepts from a controlled set as specified by vocabulary encoding scheme. Used to construct taxonomies and thesauri

  11. Metadata Vocabularies • Element vocabularies

  12. Metadata Vocabularies • Value vocabularies

  13. Application Profiles • the DCMI has shown its intention to gradually move away from dealing primarily with the “core” set of terms, moving instead to dealing primarily with community-specific application profiles • Implementers of metadata standards should be able to assemble the components that they require for some particular set of functions - and if that means drawing on components that are specified within different metadata standards, that should be possible – safe in the knowledge that the assembled whole can be interpreted correctly by independently designed applications. • The Lego metaphor, Duval et al (2002)

  14. Profile Model • A common model for expressing application profiles will be a necessary building block for the construction of reusable application profiles. • The model must not be tied to a specific metadata format, but must operate at the level of the abstract model, so that the application profile can be reused in all metadata formats.

  15. Profile Model

  16. Applying framework… • To IEEE LOM, DC and the Semantic Web

  17. Applying framework… • To IEEE LOM, DC and the Semantic Web DCAP

  18. Comments • The DCMI has progressed towards formalizing the complete abstract framework, including abstract model, vocabulary model and profile model. Similar efforts are not under way in LOM. • The most mature parts are certainly value vocabularies, where many external sources exist. Dublin Core metadata element vocabularies are also relatively mature. • In spite of the existence of many application profiles and metadata vocabularies, no formal model is usually followed in their design.

  19. Comments • LOM has a very weak notion of element vocabularies, that does not support URI identification of elements. • The LOM Data Model defines, in a single standard, both an abstract model (implicitly, at least), a metadata element vocabulary, a set of metadata value vocabularies, and a basic application profile. This is one way of expressing the well-known “monolithic” nature of the LOM standard.

  20. The DCMI Abstract Model • DCAM describes an information structure called a “description set”… • …but does not describe how to represent DC description set in concrete form • DCMI-defined “Encoding guidelines” • Formats defined by others, e.g. Eprints DC-XML • DCAM describes various types of metadata term… • …but does not specify the use of any fixed set of terms • DCMI-owned metadata vocabularies • Vocabularies owned/defined by other agencies

  21. The DC Application Profile • Specification of how to construct description sets (descriptions, statements) to serve some purpose • At core, a profile of a “description set” • a set of constraints based on E-R model of problem space • A DC Application Profile is “packet of documentation” which consists of: • Functional requirements (desirable) • Domain model (mandatory) • Description Set Profile (DSP) (mandatory) • Usage guidelines (optional) • Encoding syntax guidelines (optional)

  22. The Singapore Framework

  23. The way ahead… • Metadata Harmonization • a clear movement towards conventions based on Web architecture, leading to a strong recommendation for basing identification on URIs. • increased momentum towards describing element and value vocabularies in a Web architecture-friendly way, using the RDF Vocabulary Description language (RDF Schema) for element vocabularies and SKOS (Simple Knowledge Organization Systems) for describing value vocabularies

  24. The way ahead… • Metadata Harmonization • a clear movement towards conventions based on Web architecture, leading to a strong recommendation for basing identification on URIs. • increased momentum towards describing element and value vocabularies in a Web architecture-friendly way, using the RDF Vocabulary Description language (RDF Schema) for element vocabularies and SKOS (Simple Knowledge Organization Systems) for describing value vocabularies

  25. The way ahead… • For abstract models, the RDF does provide a framework well founded in Web architecture and a formal semantics. It is recommended that metadata specifications harmonize their models with the RDF model and, by extension, the semantic web. • For application profiles and syntaxes, developments such as ontologies and the Dublin Core Description Set Profile specification remain highly relevant. • Concrete work on harmonizing IEEE LOM and Dublin Core is currently progressing. The approach taken is that of reinterpretation of the IEEE LOM data elements in terms of the DCMI Abstract Model.

  26. References • Nilsson, Johnston, Naeve, Powell. “Towards an Interoperability Framework for Metadata Standards”. DC-2006http://www.dublincore.go.kr/dcpapers/pdf/2006/Paper39.pdf • Nilsson (ed), Harmonization of Metadata Standards. ProLEARN Projecthttp://ariadne.cs.kuleuven.be/lomi/images/5/52/D4.7-prolearn.pdf • Nilsson, Baker, Johnston. The Singapore Framework for Dublin Core Application Profileshttp://dublincore.org/documents/2008/01/14/singapore-framework/

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