Basic Structures of the Data Warehouse Analytics System Logical Schema
The Data Warehouse Analytics System uses a logical schema to isolate applications from the underlying physical database. The basic structures of the logical schema are the class, data member, and key.
The Data Warehouse schema defines the contents of the Data Warehouse. The schema has two distinct layers: Logical and Physical. The Logical layer serves as the metadata for the Data Warehouse. The Physical layer holds all the persisted objects (from the Logical schema) in the SQL Server data store.
Class
A class is a logical collection of data members. An instance of a class represents the data that was imported into the Data Warehouse. You can think of a class as a SQL Server table, with the individual instances of the class representing the rows, and the data members representing the columns.
For more information about class and data member relations, see What Are the Data Warehouse Logical Schema Relations?
Data Member
A data member is a structure that stores a piece of data. A class can contain an arbitrary number of data members that define the logical scope of the class. New data members can be added at any time after the class is created. Conceptually, a data member is similar to a column in a SQL Server table.
For more information about class and data member relations, see What Are the Data Warehouse Logical Schema Relations?
Key
A key is a data member or set of data members that uniquely identifies instances of a class. For example, the key for the OrderFormLineItems class is a combination of the private lineitem_id data member and the inherited OrderForm_Id and OrderGroup_Id data members. This means that instances of an OrderFormLineItems class include a unique identifier for the line item plus unique identifiers for the OrderFormHeader and OrderGroup classes.
After you create a class, data members, and relations, the class can be populated with data by creating a new instance of the class. You can do this with ActiveX Data Objects(ADO) by using the Microsoft OLE DB provider for Commerce Server 2009. The example provided in Extending the Data Warehouse Logical Schema uses VBScript to create new instances of the class, data members, keys, and key members.
For more information about the Commerce Server 2009 OLE DB provider, see What is the OLE DB Provider for Commerce Server?.