Glossary - A Manager's Guide to Data Warehousing - page 427

environment. An ODS can be a clean, integrated source of data to be pulled
into the data warehousing environment.
Query The mechanism to get data out of a database. A query is comprised
of constraints used to filter data out of the results, and defines the data
elements to be included in the result set and possibly some mathematical
computations, grouping, or sorting of the data.
Relational OLAP (ROLAP) OLAP technology that uses data is stored in
relational database management systems. Data is usually organized dimen-
sionally using a star or snowflake schema.
Role-playing dimension Instances of a dimension that legitimately has
more than one value for a given business transaction, such as order date and
shipped date. Each attribute with the dimension is uniquely identified to
enable easy differentiation between the different roles, such as Order Date,
Order Quarter and Shipped Date, and Shipped Quarter.
Scorecard (or performance scorecard) An application that helps organiza-
tions measure and align the strategic and tactical aspects of their businesses,
comparing organizational and individual performance to goals and targets.
Slowly changing dimension (SCD) A dimension that accommodates
changes to the reference data over time. Several dimensional modeling
techniques are used to determine how to handle changes to the reference
data stored in dimensions. This may be to retain only the current values
(Type 1), to store different versions of the reference data (Type 2), or to
retain one previous version of changes made to the entire dimension
(Type 3).
Snowflake schema A variation of the star schema in which the business
dimensions are implemented as a set of normalized tables. The resulting
diagram resembles a snowflake.
Source system An operational system of records whose function it is to
capture the transactions of the business. Source systems are often large online
transaction processing systems, but could also be smaller departmental
databases or spreadsheets that are maintained and used by members of the
business community. These are the origin of the data used to build the data
warehouse.
Staging area Place where data is stored while it is being prepared for use,
typically where data used by ETL processes is stored. This may encompass