The Governance Engine Open Metadata Access Service (OMAS) provides access to metadata for policy enforcement frameworks such as Apache Ranger. This API simplifies the internal models and structures of the open metadata type model and related structure for the consumers.
As an example, Ranger needs to know how a particular entity is classified so that the
classification can be used within a policy (rule). Apache Atlas has a complex graph-oriented model,
within which classifications can be multi level - for example a column may be classified
as employee_salary whilst employee_salary itself may be classified as SPI.
Ranger however just needs to know that the column is SPI, not how we got there.
So we convert this complex model into something much more
operationally-focused and deliver that over the API. The implementation will follow this graph,
and build up a list of all tags that are appropriate to use. Note that in the case
of Ranger it is actually the tagsync process that will call the
Governance Engine OMAS for this classification information
Ranger can do this today, but via a large number of individual requests to retrieve types and entities. Rather than these lower level queries to the metadata repository services, the Governance Engine OMAS offers result sets to make queries more efficient, and more appropriate notifications.
The module structure for the Governance Engine OMAS is as follows:
- governance-engine-client supports the client library.
- governance-engine-api supports the common Java classes that are used both by the client and the server.
- governance-engine-server supports in implementation of the access service and its related event management.
- governance-engine-spring supports the REST API using the Spring libraries.