|Oracle9i OLAP Services Developer's Guide to the Oracle OLAP API
Release 1 (9.0.1)
Part Number A88756-01
Understanding OLAP API Metadata, 4 of 10
The OLAP API implementation of the MDM model is represented by classes in the oracle.express.mdm package. Most of the classes in this package implement metadata objects, such as dimensions and measures. The following list introduces the subclasses of the MdmObject class.
MdmObjectclass has the following subclasses:
MdmSourceclass has the following subclasses:
MdmDimensionedObjectclass has the following subclasses:
MdmDimensionclass has the following subclasses:
MdmHierarchicalDimensionclass has the following subclasses:
The diagram below shows this structure.
An application accesses metadata objects by creating an OLAP API
MdmMetadataProvider and using it to discover the available metadata objects in the data store.
The metadata objects that a database administrator specifies in Oracle Enterprise Manager map directly to MDM metadata objects that are accessible through the
MdmMetadataProvider. The following table presents the typical mapping.
Oracle Enterprise Manager Objects
MDM Metadata Objects
This chapter describes the MDM metadata objects. For information about how an application discovers the available MDM metadata objects in the data store, see Chapter 4.
MdmSchema represents a set of data that is used for navigational purposes. An
MdmSchema is a container for
MdmDimension, and other
MdmSchema objects. An
MdmSchema is equivalent to a folder or directory that contains associated items. It does not correspond to a relational schema in the Oracle database. Instead, it corresponds to a measure folder, which can include data from several relational schemas and which was created by a database administrator using the OLAP management feature of Oracle Enterprise Manager.
Data that is accessible through the OLAP API is arranged under a top-level
MdmSchema, which is referred to as the root
MdmSchema. Under the root, there are one or more subschemas. To begin navigating the metadata, an application calls the
getRootSchema method on the
MdmMetadataProvider, as explained in Chapter 4.
MdmSchema contains all the
MdmDimension objects that are in the data store. That is, if the root
MdmSchema has subschemas that contain
MdmDimension objects, the root
MdmSchema also contains those objects.
MdmSchema has methods for getting all the
MdmSchema objects that it contains. The root
MdmSchema also has a method for getting the measure
MdmDimension, whose elements are all the
MdmMeasure objects in the data store.
MdmSource represents a measure, dimension, or other set of data (such as an attribute) that is used for analysis. This abstract class is the basis for some important MDM metadata classes, such as
MdmSource objects represent data, but they do not provide the ability to create queries on that data. Their function is informational, recording the existence, structure, and characteristics of the data. They do not give access to the data values.
In order to access the data values for a given
MdmSource, an application calls the
getSource method on the
MdmSource. This method returns a
Source through which an application can create queries on the data represented by the
MdmSource. The following line of code creates a
Source from an
Source that is the result of the
getSource method on an
MdmSource is called a primary
Source. An application creates new
Source objects from this primary
Source as it selects, calculates, and otherwise manipulates the data. Each new
Source specifies a new query.
For more information about working with
Source objects, see Chapter 5.
The rest of this chapter describes the subclasses of
MdmSource, along with other classes, such as
MdmDimensionMemberType, that are closely related.