Este probabil vorba despre "Data service layer
The data service layer (DSL), introduced in WebSphere Commerce Feature Pack 3.0.1, provides a layer for data access that is independent of the physical schema.

The purpose of the data service layer is to provide a consistent interface (called the data service facade) for accessing data, independent of the object-relational mapping framework (such as EJB, DAS, or JPA). In its turn, the abstracted mapping framework is used to transform the data retrieved from the database into a collection of Java objects. These objects are implemented as physical service data objects (SDOs).

The data service layer performs bidirectional transformations between physical SDOs and logical SDOs. It allows you to perform CRUD operations on the logical SDOs. Alternately, the data service layer also lets you do CRUD operations directly on the physical data, bypassing the logical schema altogether.

XPath is used as a query language on the logical schema. The data service layer maps XPath queries to templates of SQL statements. These templates are used to generate actual SQL statements which access the database.

The data service layer also allows the templates to contain business context variables, which get substituted when the SQL statements are generated. Thus, the XPath queries sent in by the client can result in different actual SQL queries, depending on the property values of the business context. The statements are stored in a separate query template file, which isolates the runtime logic from the SQL query code."

De fapt, o varianta, sau aplicatie practica in dezvoltare soft a Modelului OSI (vezi referinta a 2-a).