The Item Relations plugin lets you define relations between items. For example, you can make one item a part of another item, where "part of" is the relation. You can also make one item a "reproduction of" or a "translation of" another item.
We've bundled the plugin with common relations derived from several formal vocabularies, including Dublin Core, FRBR, FOAF, and BIBO. You may use these or create a custom vocabulary with the relations needed in your site. You could, for example, define custom relations like "is parent of," "is better than," and "fits within."
Once you have installed the plugin, you will be redirected to the configuration page. You can access these settings again by going to the Plugins menu on the top navigation, scrolling to Item Relations, and clicking on the Configure button.
Item Relations has two options for configuration:
- A checkbox (checked by default) to Append to Public Items Show. If checked, an item’s show page will also display related items.
- Relation format sets how the item relationships are shown, on public and admin pages. Your options are either the vocabulary prefix and term label (ex: dcterms:hasPart) or the label (ex: Has Part)
Customize Relationship Vocabulary
To see which vocabularies are available, or create additional vocabularies, navigate to the Item Relations tab on the left-hand navigation of your admin dashboard.
This page displays a table of the available vocabularies, their description, namespace prefix, and the namespace URI. Click on the Name of the vocabulary to view its properties (a term for the way relationships are defined)
If you wish to create your own vocabulary, edit the “Custom” vocabulary by clicking on “Edit Custom Vocabulary” in its property show page. Here you can add, edit, and delete properties in your custom vocabulary.
Once Item Relations is installed, it will add a tab to the item/edit view for items.
To add an item relation, click on that tab. You will need to know the item id of the item to which you are defining a relation; you can find this in the url of the view or edit for that item or in the heading on that page. It will be a numeric sequence. In the illustration below, the item id is 1065.
The construction of the relationship between items should make sense when read from left to right in the table. Current item is part of/is the creator of/has part/etc related item.
You may batch relate items using the Batch Edit function from the Browse Items pages in the admin.
Item Relations and RDF
The plugin follows the RDF model for defining relations between items. There's a subject item, a predicate (a relation/property in this case), and an object item. If we decompose the sentence: "Item 1 is a part of Item 2," "Item 1" is the subject, "is a part of" is the predicate, and "Item 2" is the object. These triples are the foundation of RDF. Your end users won't have to know this, but it's helpful to know it as an administrator.
Following RDF, every formal vocabulary has a namespace prefix and namespace URI, which provide unambiguous context for its relations/properties. Every property has a local part and/or label, which are machine-readable and human-readable names of the property, respectively. As an administrator you'll only need to create labels, everything else is there for XML and RDFS compliance, to be used for future output formats.