Arranging the Steps Layout

11-2 Oracle Fusion Middleware Developers Guide for Oracle Data Integrator A diagram of sources is made of source datastores - possibly filtered - related using joins. The source diagram also includes lookups to fetch additional information for loading the target. Two types of objects can be used as a source of an interface: datastores from the models and interfaces. If an interface is used, its target datastore -temporary or not- will be taken as a source. The source datastores of an interface can be filtered during the loading process, and must be put in relation through joins. Joins and filters are either copied from the models or can be defined for the interface. Join and filters are implemented in the form of SQL expressions. ■ Mapping A mapping defines the transformations performed on one or several source columns to load one target column. These transformations are implemented in the form of SQL expressions. Each target column has one mapping per dataset. If a mapping is executed on the target, the same mapping applies for all datasets. ■ Staging Area The staging area is a logical schema into which some of the transformations joins, filters and mappings take place. It is by default the same schema as the target’s logical schema. It is possible to locate the staging area on a different location including one of the sources. It is the case if the target’s logical schema is not suitable for this role. For example, if the target is a file datastore, as the file technology has no transformation capability. Mappings can be executed either on the source, target or staging area. Filters and joins can be executed either on the source or staging area. ■ Flow The flow describes how the data flows between the sources, the staging area if it is different from the target, and the target as well as where joins and filters take place. The flow also includes the loading and integration methods used by this interface. These are selected by choosing Loading and Integration Knowledge Modules LKM, IKM. ■ Control An interface implements two points of control. Flow control checks the flow of data before it is integrated into the target, Post-Integration control performs a static check on the target table at the end of the interface. The check strategy for Flow and Post-Integration Control is defined by a Check Knowledge Module CKM. The interfaces use the following components that should be created before the interface: ■ Datastores that will be used as sources and target of the loading process must be populated into the data models. See Chapter 5, Creating and Reverse-Engineering a Model for more information. ■ The correct physical and logical schemas along with their mapping in the interface’s execution context must be defined prior to creating the interface, if the staging area is to be defined in a schema different than any of the sources or the target. See Chapter 4, Setting-up the Topology for more information.