Draft of Nov 4 , 2006 . Description and Search : Metadata as Infrastructure

The first and original use of metadata is for describing documents. XML, the Dublin Core and MARC library catalog records are examples. The name “metadata” (beyond or with data) and the popular definition “data about data” is based on this use. A second use of metadata is to form organizing structures by means of which documents can be arranged. These structures can be used both to search for individual documents and also to identify patterns within a population of documents. The second role of metadata involves an inversion of the relationship between document and metadata. These structures can be considered infrastructure. The First Purpose of Metadata: Description The term “metadata” is used to denote “data about data” and its first and original purpose is to describe documents. (Here we do not distinguish between data and documents). There are different kinds of descriptive metadata: technical (to describe format, encoding standards, etc.); administrative (to describe intellectual property rights, conditions of access, etc.); and content (subject matter, scope, authorship, etc.). These descriptions characterize and explain the data. Metadata helps one to understand what the data is and how to make use of it (Caplan 2003, Haynes 2004). Metadata has two components: A format and a set of values. XML, the Dublin Core and MARC library catalog records are well-known formats and are associated with specific standards for specifying the kinds of descriptions that may be used with them. Description can be very useful, even if idiosyncratic terminology is used. Almost any description is better than none. However, it is always strongly recommended that descriptive metadata follow standardized forms, e.g. using a standard format and widely used terminology. The use of standardized formats for storing and displaying makes use of metadata easier. The use of standard vocabularies has the advantage of consistency and aids understanding. All description is a language activity even if an artificial notation, such as the Dewey Decimal Classification system, is used. Description is always and necessarily culturally-based because descriptions are based on the concepts, definitions, and understandings that have developed in a community. When you browse documents, especially digital documents, you are likely to examine descriptive metadata in order to understand what kind of document it is, what it is about, and how to use it. This process resembles the way one can look at the cover of a book to help assess the text within.