Open Metadata Archives
The open metadata archives provide pre-canned content (open metadata types and instances) to load into an open metadata repository. There are two main types of open metadata archive:
- Content packs - read only metadata types and instances that are reusable in many organizations.
- Metadata exports - metadata exported from a specific open metadata repository that can act as a backup. It is read-write if loaded into an open metadata repository with the same metadata collection id as the originating repository, or read-only if loaded into a repository with a different metadata collection id.
Figure 1 shows a content pack being loaded into a metadata repository. It is stored in the local repository and distributed around any connected cohorts. These types of archives can be provided by the Egeria community and third party organizations.
Figure 1: Loading a content pack
When data and other types of assets are being transported between organizations, it is possible to use a metadata export open metadata archive to pass the related metadata as well. This is shown in figure 2.
Figure 2: Exporting and reimporting metadata between unconnected repositories
Figure 3 shows a metadata export archive to create a backup of selected metadata. This can be used to recover the metadata repository content after a bad load or other operational error.
Figure 3: Selective back up of metadata elements
Creating open metadata archives
Open metadata archives are created through Java utilities. There are two approaches:
Content packs are created using the repository services archive utilities. The Egeria supported utilities for open metadata archives described at the bottom of this page use this approach.
Metadata export archives are created by using the repository services clients to extract the metadata elements from a live repository and the to store them in the archive using the repository services archive utilities.
Loading open metadata archives
A metadata server’s configuration document can list the archives to load each time the server is started. This is useful if the server does not retain metadata through a server restart (like the in memory metadata repository). Open metadata archives may also be loaded while the server is running using a REST API call.
The archive is loaded once and its content is immediately available. If the repository persists metadata over a server restart then this archive content continues to be available after the server restarts.
It does not matter how many times an archive is loaded, only one copy of the content is added to the repository.
Inside an Open Metadata Archive
The open metadata archive has three parts to it. This is shown in Figure 4. The header defines the type of archive and its properties. Then there is the type store. This contains new types and updates to types (patches). Finally there is the instance store. This contains new instances (entities, relationships and classifications).
Figure 4: Inside an Open Metadata Archive
The archive loads in the following order:
- Attribute Type Definitions (AttributeTypeDefs) from the type store.
- New Type Definitions (TypeDefs) from the type store.
Updates to types (TypeDefPatches)
- New Instances
Supported utilities for open metadata archives
Egeria supports the following open metadata archives. Associated with each archive are utilities that help you build additional archives of your own content.
Open Metadata Types - the Egeria Open Metadata Type Definitions. This archive is always loaded by each OMAG metadata repository server at start-up. This is to reduce the chance that new types developed by a third party have names that conflict with the open metadata types. There is also a utility to create the archive file for these open metadata types. The find out more about the Open Metadata Types click here.
Open Connector Archives - provides utilities for building open metadata archives containing information about one or more connectors that follow the Open Connector Framework (OCF). In addition, there are utilities for building an open metadata archive containing the connector type definitions for Egeria’s data store connectors.
More information about the processing of open metadata archives can be found in the repository services documentation module.
In addition these Administration Guide articles may be of interest:
- Configuring an open metadata archive in an OMAG Server
- Adding an open metadata archive to a running OMAG Server
License: CC BY 4.0, Copyright Contributors to the ODPi Egeria project.