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Basic Structures of the Logical Schema

Commerce Server 2002

The Commerce Server Data Warehouse uses a logical schema to isolate applications from the underlying physical database. The logical schema defines the conceptual infrastructure of the Data Warehouse. The basic structures of the logical schema are the class, data member, and key.

Class

The class is fundamental to the Data Warehouse logical schema. A class is a logical collection of data members. An instance of a class represents the user data 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 Describing Data Warehouse Logical Relations.

Data member

A data member 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 analogous to a column in a SQL Server table.

For more information about class and data member relations, see Describing Data Warehouse Logical 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 creating a class, data members, and relations, the class can be populated with data by creating a new instance of the class. This can be accomplished with ActiveX Data Objects(ADO) by using the Microsoft OLE DB Provider for Commerce Server. 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 OLE DB Provider, see About the OLE DB Provider for Commerce Server.

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