Scope System Analysis Oracle Tips by Burleson Consulting

The Data Warehouse Development Life Cycle

The Scope Of Work Agreement 

Of course, developers are not going to know all of the details about a proposed warehouse until system analysis has been completed, but developers need to carefully document the details that are known at this point. For example, details may include:

* A description of the data sources for loading the warehouse. This may specify that the data sources reside in IMS hierarchical databases, DB2 mainframe relational databases, Oracle Unix databases, ISAM flat files, or any other data sources. Legacy and OLTP data sources need to be identified as a part of the SOW, as well, so the project can justify any human resources needed for data extraction tasks. For example, data extraction from an IMS database requires an IMS programmer with DL1 skills, while extraction from an IDMS database requires the services of an MVS systems programmer and an application programmer who understands JCL, IBM mainframe utilities, and CODASYL DML programming.

* A description of the basic data elements of interest to the warehouse users. This description incorporates the facts that will constitute the data warehouse and consist of the definitions of numeric items, such as sales amounts, inventory levels, and net revenue. Even for a warehouse that consumes terabytes of disk storage, there may only be a small handful of these facts that are being tracked. The size of the warehouse comes from the wholesale de-normalization of the facts with their data attributes.

* A description of the “dimension” attributes. Dimension attributes are non-fact items that lend value to a fact, such as a date, an item type classification, or a sales district. The dimension attributes for facts are critical to the implementation of the data warehouse. The SOW must describe each of these attributes and how attributes may be nested within other attributes. (For example, end-user management may want to see summary sales of states within districts, within regions.) Many warehouse development managers include classification hierarchies in the SOW to clearly identify the nature of the attributes relation to other data attributes.

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This is an excerpt from "High Performance Data Warehousing", copyright 1997.

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