SPIKE: Explore consolidating instance relationships, related instances and preceding / succeeding titles

Current Situation

During the development of the related instances work, a suggestion was made to consolidate each of the following together because they are structurally similar:

• instance relationships
• preceding / succeeding titles
• related instances

Instance relationships: why and terminology

Scope

General Proposal

• Consolidate all of relationship types into a single reference record set
• Introduce a relationship type group reference record set
• Figure out how to identify direction of relationship in a general way e.g. A -> B means something different to B -> A and thus needs different headers etc

Other Considerations

• Migrating existing relationships during a single module upgrade

More Detailed Proposal

Existing instance relationships: how they work and can they be combined?

Questions

• Do cataloguers / metadata managers consider these to be the same idea (and only grouped in different ways)?
• Can all of these be linked or unlinked (an instance at only one end)?
• Are all of these blocked when the source of the instance is MARC?
• Are there variations between how these work / are presented e.g. not all have a media type?
• Should the business logic API expose these as a single (or two for direction) collection or provide a collection per group?
• How does the back end / UI identify specific groups in order to treat them differently?