# Extent Mapping Page

There are data, related with one entity data type pair (ARM and AIM), represented. Data can be merged from several models (in the case that you are working on the schema instance instead of the model).
The lis of models is represented in the Model combobox on the top section of the window. Names of the ARM entity data type and the AIM entity data type are represented in the appropriate Source (ARM) and Target (AIM) fields. The current model, situated in the Model combo box will be changed into the instance model automatically after you select an instance. The instances, which fits with the mapping of both ARM and AIM entity data types, and are in these models are listed in the Instances layout.
You can create instance of the type you need by selecting a model, in which the instance is to be created, and pressing 'Create' button. If you want to delete an instance you need to select it and press 'Delete' button. 'Get' button is for further editing operations. Select instance and press 'Get' button, then the selected instance will be placed in the SDAI clipboard andy ou will be able to use a 'Add' operation later. More for editing see instance mapping.