Developing Metadata Standards

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Developing Metadata Standards

• Cleo Sgouropoulou
• email csgouro_at_cs.ntua.gr

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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.

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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.

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A framework for MS
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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.

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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.

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Abstract Model Standards
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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)

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Metadata Formats
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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 (dctitle, dcsubject, 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

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Metadata Vocabularies

• Element vocabularies

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Metadata Vocabularies

• Value vocabularies

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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)

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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.

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Profile Model
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Applying framework

• To IEEE LOM, DC and the Semantic Web

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Applying framework

• To IEEE LOM, DC and the Semantic Web

• DCAP

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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.

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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.

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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

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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)

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The Singapore Framework
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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

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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

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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.

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References

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