Model Mapper

Using the mapper

Displaying and arranging the Mapper

When the mapper is started the windows are aligned in the following way:

• the source models are displayed on the right,
• the destination model is displayed on the left, and
• the mapping window is displayed in the middle.

If the destination model is also a source, all models are displayed on the left with the destination model on top of the arrangement. There are several ways to align the Model mapping with the source and the destination models. This is chosen by right clicking on the Model Mapping object to display the Model Mapper menu and choosing the sub-menu Layout. You can use one of the three menu entries, Maximize, Cascade or Align with models, to arrange the Model Mapping components.

Fig. 1. Mapper display with four sources one of which is also a destination

Automapping Models

Generally, when the models are basically identical, and you simply wish to inform the repository of that fact, you then want to create a stitiching between the two or more references to the same model. In this case, simply right-click on the mapping format and select the Automap Models option. This action will invoke the comparator and mapper, and autopopulate the mapping format where the models are identical.

Defining Mapping Objects

You may, of course, create or edit mappings by hand. There are two main mapping objects that can be created to map the classes, attributes and keys of the source and destination models. When a model mapping is generated from the model comparator, some of these objects are automatically created.

• Classifier Map - For each destination class a mapping is described, this is called a Classifier Map. Several mappings may be defined for a given destination class/entity/table/dimension (a good example is given in the Metadata Management Tutorial). A classifier map will contain all of the additional structures that are needed to describe the mapping and potetially the transformations that are defineds between the source and the destination.
• Feature Map - In a classifier map, the Feature Maps describe the relationships and potentially the transformations that are defined between a given set of source attributes and destination attributes. The comparator will only define equal operations whereas more complicated transformations may be defined.

Fig. 2. Mapper display: Creating Mapping Objects

In the above figure, the source model (an ETL model) is mapped to the model of a data warehouse. The mapping window contains information about the current state of the mapping. The entry Add source classifiers... in the Model Mapper menu allows you to manually select the destination classes for which you want to create a class map. The dialog box that let you choose the destination classes

Once a classifier map is created, you can add source classes using the Add Source Classes... menu entry in the popup menu of the class map. You can add feature maps using the Add Feature Maps... menu entry.

Feature Maps correspond to the attribute level mappings transformations that are defined to relate the data to the destination class. In general there will be as many Feature Maps as there are attributes in the destination class but there may be transformations that will have several destination attributes. To add destination attributes to an object, you must first copy the attribute from the source or destination window and paste it on the object that is in the mapping window. The one constraint is that the destination attribute be copied first, so we know which destination attribute is mapped. For example, the highlighted object Account Status has two classes connected: the source class with the solid left arrow and the destination class with the solid right arrow. The solid arrow suggests the node is linked to another in a different window, in this case, the models in the source and destination window.

You need only right click on a selected object (classifier map, feature map) to:

• Add source or destination objects,
• Remove source or destination objects,
• Edit the properties specific to this object (description for all objects, operation for a classmap or attribute map...)
• Paste link...other objects (for example a source or destination object) to this object,
• Delete the object,
• Rename the object to a perhaps more meaningful name.

Defining Feature Maps

Creating and Editing Feature Maps

A Feature Map may have several source and several destination attributes.
To create a Feature Map for a destination attribute, right click on the Classifier Map then select the Add Feature Maps option.
To add a destination attribute to a Feature Map, right click on the object then select the Add source Features option. When adding the first source attribute, the equals operation will be proposed if there is only one destination attribute and if their types are similar.

Defining Classifier Maps

Creating and Editing Classifier Maps

Source Class(es) can be added to the Classifier Map using the Add Source Classes... option that is available via a right mouse click on the Classifier Map. The Class can also be added to a class map by either copying the source class to the Class Map or by adding source features to a Feature Map of the class map. Any source features may be copied to a Feature Map. The source class will then be added to the Classifier Map.