Open Metadata Access Services (OMAS)

The Open Metadata Access Services (OMAS) provide domain-specific services for data tools, engines and platforms to integrate with open metadata.

The access services are as follows:

Inside an OMAS

Figure 1 shows the typical structure of an OMAS. Tools, applications and engines can connect to an OMAS through its API or use its topics to either post metadata to the open metadata repositories or receive notifications about metadata changes.

Figure 1

Figure 1: Anatomy of an Open Metadata Access Service (OMAS)

Every OMAS supports a Java client interface that runs locally in the metadata tool, engine, or application. These client interfaces support calls to the REST API and provide message helpers for the OMAS In and Out Topics. They can be downloaded and used independently with the Egeria Client Package.

For callers that do not use Java, there is an OMAS REST API and an event notification interface (typically supported by Apache Kafka) behind the Java client interfaces that can be called directly. The event notification interface for each OMAS has a topic to allow an external caller to post metadata updates to the open metadata repositories (OMAS In Topic) and another topic (OMAS Out Topic) to receive relevant updates that have come from other parts of the open metadata and governance ecosystem. These topics are handled by the OMAS Event Listener and OMAS Event Publisher respectively.

Both the REST API and the topics interact with the OMRS to receive and send metadata to the open metadata repositories, either by receiving messages on the OMRS Topic or by calling an OMRS Connector. The type and configuration of the OMRS Connector (and hence which metadata repositories it connects to) is set up when the OMAS APIs are deployed.

The OMAS APIs are deployed together in a single web application. This application can be co-located with a metadata repository, or can be deployed independently (see Open Metadata Integration Patterns to understand the options). The implementation of the OMRS Connector handles the communication between the OMAS application and the metadata repositories, whether this is through local or remote calls.

The administration services provide the ability to configure, start and stop the access services.

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License: CC BY 4.0, Copyright Contributors to the ODPi Egeria project.