Table of Contents

Entity Relationships

This explains Entity Relationships. For an overview check out Understanding Data....

Data can be related to other data, like when a Book belongs to a Category and also has an Author. Since all data-items are called Entities we call this Entity Relationships.

Additionally, there are also Entities which explicitly enhance/describes another thing. That kind of relationship is called Metadata.

How Entity-Relationships Work

Each Entity has many fields, some containing text, numbers etc. but some can also point to another item. These kinds of fields are called Entity Fields. When configured correctly, an entity-field shows a dropdown of items. So in the case of a book, the Author field may show a dropdown of Person items.

There are different types of relationships:

  • 1:n means that one thing can refer to many other things - like a book which points to many categories
  • n:1 means that many things can refer to one thing - like many books pointing to the same author
  • n:n means that many things can refer to many things - like many blog-posts pointing to many tags (the blog can refer to many tags, and each tag may be pointed to by many blogs)
  • 1:1 relationships are when one thing refers to one other thing, and neither are re-used again. This is not often used in CMSs.

Relationships Preserve Item-Order

Since 2sxc/EAV data is often used for Content-Management it's important to note that:

Relationships preserve the Order of the Related Items.

This means that an editor adding Author relationships to a Book can organize them in an order if he/she wishes to do this.

The output template can then choose to either output these Authors in the order they were managed, or sort them by Title or other property if that would be more appropriate.

Relationships are Cross-Language

Values of Entities are multi-language, but relationships-connections apply to all languages. So the list of Authors is the same for all languages.

Metadata Relationships

This is a very different concept, where an Entity enriches something else. Read more about it in metadata.

Advanced Topics

History

  1. Introduced in 2sxc 2.0
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