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Node Concepts

This page describes the core fields and features that Islandora uses to manage content as nodes in an Islandora repository.

Nodes hold metadata

In Islandora, Drupal nodes are created to hold descriptive metadata about content in the repository. This metadata is held in the usual way for nodes, which is by populating Drupal fields. Fields are configured on a Drupal content types, which serve as metadata profiles.

Nodes can have members/children

To build the capacity for creating hierarchical structures like collections, books and their pages, and complex objects, Islandora introduces a special field, "Member of" (field_member_of) which must be present on all Islandora content types. It enables a "Children" tab to display on Islandora nodes which lists the children of that node, and allows a repository manager to perform bulk operations on them. It also enables a repository manager to create children of nodes directly, individually or in bulk.

Nodes have models

Within a single content type (i.e. metadata profile), Islandora provides the ability to designate some objects as different "types" than others. Key behaviours, such as what derivatives are created or what viewer is used, can be configured (see Contexts) based on this value. The available values are taxonomy terms in the Islandora Models vocabulary, and they are attached to nodes via the special mandatory field, "Model" (field_model), which must be present on all Islandora content types. These values are installed through a Drupal Migration after the Islandora module is installed. All installation methods perform this migration, so out of the box, the following values should be available in the Islandora Models vocabulary:

Name External URI
Digital Document
Paged Content
Publication Issue
Compound Object

With Islandora alone, choosing a value from this list will have zero effects. The contingent behaviour must be configured during repository implementation. Islandora Starter Site provides an example of what behaviours are possible for these types.

The External URI field

This vocabulary, like many others in Islandora, includes an External URI field. This is intended to be used when transforming Islandora content into RDF, but also serves to make it easier to share configuration. Islandora provides code so that context conditions and derivative configs can be created without referencing the taxonomy term by ID, rather, using the taxonomy term's External URI. Since terms IDs are likely to change across sites, this makes our configs more portable.

Nodes are attached to Media

In an Islandora repository, the files in the repository are uploaded as Media, which are linked to the node providing the descriptive metadata. Media belonging to a specific node can be found in the Islandora-provided "Media" tab on that node. For more, see the [Media in Islandora] section.

Last update: May 17, 2024