For a binary operation (i.e., Product, Intersection, Difference, Join, or Union) the target relations may be be chosen from two drop-down lists; and the operation is declared after the OK-button is pressed. For a unary operation (i.e., Selection, Projection, or Renaming) one target relation and some additional information must be specified. In the case of Selection operation, a table is provided where the user can enter a list of selection conditions (e.g., city='Boston'). For the Projection operation, a table with the attributes of the target relation is provide. Each attribute has a corresponding check box to indicate whether the attribute is to be projected. For the Renaming operation, the current attribute names of the target relation appear in the first column of a table. The new names of the attributes may be entered in the second column of the table.
To save the query and/or its result, the save button in the Query Dialog may be pressed, and the Query Name Dialog appears. The user may refer to the above description on the Query Name Dialog for the following steps. The query and its result are stored in the relation repository and query repository, respectively.
Figure 14: difference dialog of CDB
Figure 13: intersec dialog of CDB
Figure 12: union dialog of CDB
Figure 11: join dialog of CDB
Figure 10: product dialog of CDB
Figure 15: selection dialog of CDB
Figure 16: projection dialog of CDB
Figure 17: renaming dialog of CDB