|Oracle9i OLAP Services Developer's Guide to the Oracle OLAP API
Release 1 (9.0.1)
Part Number A88756-01
Understanding OLAP API Metadata, 3 of 10
Using the Oracle Enterprise Manager graphical user interface for OLAP management, a database administrator adds metadata to a data warehouse. The end result, within the graphical user interface, is the creation of one or more measure folders that contain one or more measures. The measures have dimensions, and the dimensions have hierarchies, levels, and attributes. Each of these OLAP objects maps directly to an MDM object in the OLAP API.
The collection of warehouse data for which a database administrator has created metadata using the OLAP management feature of Oracle Enterprise Manager is referred to as the data store to which the OLAP API gives access.
For detailed information about using the OLAP management feature of Oracle Enterprise Manager, see the Oracle Enterprise Manager Help system.
Note that the OLAP management feature includes a cube object which does not map directly to any MDM object. Database administrators use cubes in Oracle Enterprise Manager to specify the dimensions of each measure, as well as other characteristics. Once the dimensions are specified, they are firmly associated with their measures in the metadata, so this type of cube object is not needed in the MDM model.
Database administrators also work with materialized views in the OLAP management feature of Oracle Enterprise Manager. These are relevant to query optimization, but they do not map to objects in the MDM model.
The rest of this topic briefly describes the OLAP management objects in Oracle Enterprise Manager that map directly to MDM objects in the OLAP API.
The dimension property sheet in the OLAP management feature of Oracle Enterprise Managergives a database administrator the ability to specify the following for a given OLAP dimension.
Typically, a database administrator specifies one or more columns in a database table to serve as the basis for each OLAP level, hierarchy, and attribute.
A database administrator creates cubes after creating dimensions. A cube is a set of dimensions that provide organizational structure for measures. When database administrators are adding a dimension to a cube, they can specify an alias for the dimension.
The cube property sheet in the OLAP management feature of Oracle Enterprise Manager gives a database administrator the ability to specify that a given measure belongs to a given cube. Because a cube is a set of dimensions that provide organizational structure for measures, specifying that a given measure belongs to a given cube specifies the dimensions of that measure. This is essential information for the OLAP API, where the dimensionality of a measure is one of its most important features.
To identify the data for a measure, the database administrator typically specifies a column in a fact table where the measure's data resides. As an alternative, the database administrator can specify a calculation or transformation that produces the data.
Once a database administrator has created measures (first creating dimensions and cubes), the next step is to create one or more groups of measures called measure folders. Typically, the measures in a given folder are related by subject matter. That is, they all pertain to the same business area. For example, there might be three separate folders for financials, sales, and human resources.
The measures in a given measure folder can belong to different cubes, and they can be from more than one schema.
The database administrator must create at least one measure folder because the scope of the data that an OLAP API application can access is defined in terms of measure folders. That is, an OLAP API
MdmMetadataProvider gives access only to the measures that are contained in measure folders. Of course, each measure's dimensions are included, along with its hierarchies, levels, and attributes.
In this context, it is important to understand that measure folders can be nested. This means that a given measure folder can have subfolders that have their own measures, and even their own subfolders. Thus, a database administrator can arrange measures in a hierarchy of folders, and an OLAP API
MdmMetadataProvider can give access to all of the measure folders and their subfolders.