Workbook on Digital Private Papers > Administrative and preservation metadata > Using METS for the preservation and dissemination of digital archives

Using METS for the preservation and dissemination of digital archives

Introduction

During recent years an increasing quantity and variety of digital material has been created or held by libraries, and consequently many standards have been developed to encode different categories of metadata for specific object types. There is no catch-all standard which accommodates the needs of every digital object type, and the lack of consensus on which standards to use can cause interoperability problems, especially when metadata or objects need to be transferred between repositories. As well as metadata specific to particular object types, all digital objects require different levels and types of metadata at different points in their lifecycle; all of this diverse metadata needs to be associated or packaged with the object it describes.

The Metadata Encoding and Transmission Standard (METS) was developed to deal with these issues. It is an XML Schema designed as an overall framework within which all the metadata associated with a single digital object can be stored or referred to. It enables effective management of digital objects within the repository, acts as a standard for transferring metadata within repositories, facilitates access and navigation by the researcher, and links the digital object and its metadata inextricably together. METS offers significant benefits to archivists, but its usage will not solve interoperability problems; only agreement on common METS profiles can do this.

METS is intended to act as an Information Package, as defined by the Reference Model for an Open Archival Information System (OAIS). It can deal with all the categories of metadata specified by OAIS as necessary to the preservation of a Content Data Object, i.e.

A METS file contains separate sections for descriptive, administrative and structural metadata; each section is linked to the others by means of a comprehensive system of unique identifiers. It allows two approaches to the storage of descriptive and administrative metadata: they can either be held internally within the METS file, or held externally and referenced from within the file. While METS does not dictate the content of the metadata, the METS Editorial Board recommends a number of other metadata schemas (known as Extension Schemas) which can be incorporated into the METS file or referred to from it.

A general introduction to METS for archivists is provided here in order to examine how it might be used to hold all of the metadata that must be captured for the kinds of digital objects typically found in personal archives. The suggestions made derive from Paradigm's experiences; they do not constitute a fully drafted METS profile, but provide a basis to build on.