Project: Backstage (App Definition and Development / Application Definition & Image Build)
File: well-known-relations.md

id: well-known-relations title: Well-known Relations between Catalog Entities sidebar_label: Well-known Relations description: Documentation that lists a number of well known Relations, that have defined semantics. They can be attached to catalog entities and consumed by plugins as needed. This section lists a number of well known , that have defined semantics. They can be attached to catalog entities and consumed by plugins as needed. If you are looking to extend the set of relations, see . This is a (non-exhaustive) list of relations that are known to be in active use. Each relation has a source (implicitly: the entity that holds the relation), a target (the entity to which the source has a relation), and a type that tells what relation the source has with the target. The relation is directional; there are commonly pairs of relation types and the entity at the other end will have the opposite relation in the opposite direction (e.g. when querying for `A`, you will see `A.ownedBy.B`, and when querying `B`, you will see `B.ownerOf.A`). An ownership relation where the owner is usually an organizational entity ( or ), and the other entity can be anything. In Backstage, the owner of an entity is the singular entity (commonly a team) that bears ultimate responsibility for the entity, and has the authority and capability to develop and maintain it. They will be the point of contact if something goes wrong, or if features are to be requested. The main purpose of this relation is for display purposes in Backstage, so that people looking at catalog entities can get an understanding of to whom this entity belongs. It is not to be used by automated processes to for example assign authorization in runtime systems. There may be others that also develop or otherwise touch the entity, but there will always be one ultimate owner. This relation is commonly generated based on `spec.owner` of the owned entity, where present. A relation with an entity, typically from a . These relations express that a component exposes an API - meaning that it hosts callable endpoints from which you can consume that API. This relation is commonly generated based on `spec.providesApis` of the component or system in question. A relation with an entity, typically from a . These relations express that a component consumes an API - meaning that it depends on endpoints of the API. This relation is commonly generated based on `spec.consumesApis` of the component or system in question. A relation denoting a dependency on another entity. This relation is a general expression of being in need of that other entity for an entity to function. It can for example be used to express that a website component needs a library component as part of its build, or that a service component uses a persistent storage resource. This relation is commonly generated based on `spec.dependsOn` of the component or resource in question. A parent/child relation to build up a tree, used for example to describe the organizational structure between . This relation is commonly based on `spec.parent` and/or `spec.children`. A membership relation, typically for in . This relation is commonly based on `spec.memberOf`. A relation with a , or entity, typically from a , , , or , These relations express that a component belongs to a larger component; a component, API or resource belongs to a system; that a system is grouped under a domain; or that a domain belongs to a larger domain. This relation is commonly based on `spec.system` or `spec.domain`.