The intent of specifying this element is to provide a means to express relationships among resources that have formal relationships to others, but exist as discrete resources themselves. For example, images in a document, chapters in a book, or items in a collection. Justifications and Uses Digital resources are rarely published in isolation. Most are published as part of a collection of related resources. For example, HTML pages are often published in hyper-linked webs, and images are often published in thematic galleries.
Much intellectual effort is spent organising collections.
Part of this organisation is a description of the relationships between resources in the collection. This organisation allows users to discover resources in a structured way. For example, users can browse through a library collection using the subject headings in the catalog until they find a subject of interest to them. Some resources have their relationship to other resources embedded within them. For example, a hypertext link within a HTML page describes a relationship to another resource.