Open Metadata Repository Services

Open Metadata Repository Services

The open metadata repository services include 3 REST APIs, one event payload and a metadata archive format.

• Open Metadata Repository Type Management REST API
• Open Metadata Repository Instance Management REST API
• Open Metadata Repository Interchange REST API
• Open Metadata Repository Services Event
• Open Metadata Archive Format

They are described below.

Open Metadata Repository Type Management

The open metadata repository type management REST API supports the maintenance and query operations for metadata type definitions. There are three principle categories of metadata type definitions:

• Entity Type Definitions (EntityDefs) - that describe the types of entities (objects, people, actions, ...) stored in the metadata repository.
• Relationship Type Definitions (RelationshipDefs) - that describe the allowable types of relationships between each type of Entity.
• Classification Type Definitions (ClassificationDefs) - that describe the allowable types of classifications for an entity. Classifications tag entities to indicate they have a specific characteristic. This can be used to group entities that need similar governance treatment.

Collectively the EntityDefs, RelationshipDefs and ClassificationDefs are called typeDefs. Each typeDef can include attributeTypeDefs in its definition. These describe the types of properties that can be stored in the corresponding entities, relationships and classifications. AttributeTypeDefs support the definitions of simple primitive properties such as strings and integers, collection properties such as arrays, sets and maps and enums.

With the open metadata repository type management REST API it is possible to define and query the typeDefs and attributeTypeDefs supported by a repository.

Open Metadata Repository Instance Management REST API

The open metadata repository instance management REST API supports the creation, update, delete and query of metadata instances (entities, relationships and classifications) in the metadata repository.

Open Metadata Repository Interchange REST API

The open metadata repository interchange REST API supports the storing of read only copies of metadata from remote repositories and the resolution of conflicts between metadata from different repositories. This API is only used when metadata is being exchanged between repositories registered with an open metadata repository cohort.

Open Metadata Repository Services Event

The open metadata repository services event is used in the asynchronous message exchange between metadata repositories that support the open metadata standards (referred to as open metadata repositories). An open metadata repository cohort is a group of repositories that are exchanging metadata through asynchronous events and federated queries. A repository can register and unregister with a cohort at any time. The registration process passes configuration information to all members of the cohort to ensure each can communicate with the other.

There are three categories of open metadata repository services events (also known as OMRS Events):

• Registry events - For registering or unregistering an open metadata repository as a member of an open metadata cohort.
• TypeDef Events - For validating that the types used by each of the cohort's members are compatible.
• Instance Events - For exchanging reference copies of metadata instances between members of the cohort. Open metadata repositories may store reference copies of metadata from other repositories to speed up metadata queries or ensure metadata is available during an outage of the originating (home) metadata repository.

Open Metadata Archive Format

An open metadata archive is a JSON file containing open metadata. This may be both types and instances. They are used to provide collections of standard metadata elements that can be shared and reused by different organizations.