In an enterprise, there are often numerous data management systems that contain specific data for different domains. These data silos are often difficult to integrate when creating a holistic view of the data life cycle. This post will detail how to create a web services layer over existing databases that will expose DDI metadata. DDI is an open standard for documenting the data lifecycle. Using DDI, multiple data sources can be combined to create the ‘big picture’ view.
The Read Only View
The simplest way to expose DDI from an existing system is to create a Web Services facade. This facade will implement several functions that are needed to expose a data source as an ISO 11179 repository, a standard on which DDI is based. One option is to allow the existing system to perform all updates and management of its own data, while providing a read only view to other systems for integration. To accomplish this with DDI and Colectica, the following abilities should be present in the web services facade.
Viewing an Item
The most basic function of a repository is to retrieve an item. In Colectica, this will most likely be an item serialized as DDI 3. Given an ISO 11179 international registration data identifier (IRDI), the web service calls GetItem and GetItems will return a RepositoryItem object containing information about an Administered Item and its XML serialization.
An ISO 11179 repository manages multiple versions of Administered Items. The web service call GetVersionHistory can list all versions of an item in a repository.
Relationships and Search
Searching for relationships between items is needed to efficiently browse items in a hierarchy. To enable a read only view, the web services facade should implement GetRelationshipBySubject and GetTypedRelationships, and GetSet to enable relationship searching. To enable text based searching, the web services facade should implement Search and SearchTypedSet.
Often when browsing, only basic information about an item is needed for display. This often includes the item type, its identity, and a basic label. Implementing GetRepositoryItemDescriptions to provide this basic information can speed up user interactions with the web services layer.
These 9 abilities encompass all that is needed to create a read only view on top of an existing data management system. These functions also enable creation of local checkouts of the items.
- If the system already manages items using the DDI standard this is very straight forward.
- If the system manages data in the DDI content model but not in a DDI serialization of versioning system, a translation layer may be required for the serialization and identification beneath the web service facade.
- If the data managed by the system is not part of the DDI content model, the data should most likely not be put behind a web services facade. It should instead be documented using the DDI standard. This includes describing variables, datasets, and concepts that describe the data.