Towards an interoperability framework for metadata standards

model, metadata formats, metadata vocabularies, the vocabulary model, application profiles and the profile model. Some of these components correspond to concepts that have been formalized by DCMI (as DCMI recommendations or other documents); other components represent abstractions based on current usage of Dublin Core metadata and on current directions in metadata interoperability. 3.1 The Abstract Model The abstract model specifies the concepts used in the framework, the nature of terms and how they combine to form an information structure. An early effort to produce such framework for Dublin Core was presented in Bearman, Miller, Rust, Trant and Weibel (1999). Subsequently the DCMI Usage Board developed the “DCMI Grammatical Principles” (DCMI Usage Board, 2003), as a summary expression of the key concepts underpinning the vocabularies developed by the DCMI. The DCMI Abstract Model, published in March 2005, was a substantial reformulation and clarification of these principles. The DCMI Abstract Model defines the description set as the principal information structure used in Dublin Core metadata. It describes the nature of the components that make up that information structure and it also describes how that composite information structure is to be interpreted. In summary, a description set is described as follows: • a description set is made up of one or more descriptions • a description is made up of • zero or one resource URI and • one or more statements • a statement is made up of • exactly one property URI and • zero or one reference to a value in the form of a value URI • zero or more representations of a value, each in the form of a value representation • zero or one vocabulary encoding scheme URI • a value representation is either • a value string or • a rich representation • a value string may have an associated value string language • a value string may have an associated syntax encoding scheme URI • each value may be the subject of a related description A DC metadata description set is to be interpreted as a set of assertions about the resources identified by those URIs, principally about the relationships between the two resources identified by the resource URI and the value URI. The abstract model is the key used by a metadata application to unlock the secrets of 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.