The WebFOCUS Visual Discovery AE Data Pool contains all data loaded into WebFOCUS Visual Discovery AE. The Data Pool consists of tables containing collections of fields. Tables may manipulated and related in a variety of way. The WebFOCUS Visual Discovery AE Link Wizard guides you through the process of linking two tables in the data pool or performing a link operation, such as a table copy or roll-up. Existing links may also be modified.

A link is a relationship between the data of two or more tables/fields in the data pool.

1. To display the Link wizard, click in the Project Workshop toolbar.

   Note: The Data Links section is not enabled until at least two tables have been loaded into the application.

2. The Welcome page of the Link Wizard displays. Click Next.
3. The Select Link Option wizard page displays. Selection options include:
   • Create Selection Link. A selection link connects two tables in the data pool across a common key (field) so that data selection in the origin table is automatically propagated to the destination table. Keys do not need to have a 1:1 relationship. If multiple rows in the source table map to 1 or more rows in the destination table, the :highest selection state (selected, then unselected, then excluded) is used. Selection links copy state from one table to another; use two links if either table may be selected. A selection link may also be used by a bar chart to explicitly represent unmatched rows with a special bar.
   • Create Color Link. A color link connects two tables in the data pool across a common key (field) so that color assignment in the origin table is automatically propagated to the destination table.
   • Perform Table Copy. This operation makes fields from a table (the source) available in a second table (the destination) where values of a key field match. This is similar to the join operation in relational databases. Copies are done in a way that minimizes memory use, so they require less space than simply copying data to the destination table would require.
   • Perform Table Roll-Up. This operation generates a new table of data aggregated over a specific field in the origin table. This is a new table which is unaffected by changes to the source table after its creation. Selection state and color can be propagated between these tables using separate selection and color links.

     Click Next.

4. If you selected Create Selection Link:
   • The Select Link Origin wizard page displays. From the pulldown list, select a origin Table and Field Key. The Excluded rows in the Origin table cause rows in the Destination table with matching keys to also be excluded option controls how the link handles hidden/excluded rows in the origin table. If this option is selected (it is by default), then the corresponding rows in the destination table will be hidden/excluded as well. If unselected, then the state of the corresponding rows in the destination table will not change even if the hidden/excluded state of rows in the origin table do. Click Next.
   • In the Select Link Destination wizard page, select a destination Table and Field Key using the pulldown lists. The Keys in the Destination table but not in the Origin table are excluded option controls what to do with key values that appear in the destination table but not in the origin table. By default, this option is unselected. If this option is selected, then rows that appear in the destination table but not in the origin table will be hidden/excluded. Otherwise, these destination rows will remain. Click Next.
   • Enter a unique Identifier in the Specify Link or Operation Name wizard page or allow a default name to be created. Optionally, you can click the Create as a two-way link check box to specify the link propagates selection in both directions between origin and destination tables, or create a color link between the tables.
   • The Completing Link Wizard page displays. Click Finish.
5. If you selected Create a Color Link:
   • The Select Link Origin wizard page displays. From the drop-down list, select an origin Table and Field Key. Click Next.
   • In the Select Link Destination wizard page, select a destination Table and Field Key using the drop-down lists. The Apply to unmatched values in the destination table option controls what to do with key values that appear in the destination table but not in the origin table. By default this option is unselected. If this option is selected, then rows that appear in the destination table but not in the origin table will be shown with the standard missing color. Otherwise, the destination rows will remain unchanged. Click Next.
   • Enter a unique Identifier in the Specify Link or Operation Name wizard page. Optionally, you can click the Create as a two-way link check box to specify the link propagates color setting from either the origin or the destination table. This option should rarely be used.
   • The Completing Link Wizard page displays. Click Finish.
6. If you selected Perform Table Copy:
   • The Select Link Origin wizard page displays. From the drop-down lists, select a origin Table and Field Key. Click Next.
   • In the Select Link Destination wizard page, select a destination Table and Field Key using the drop-down lists. Fields from the Origin table will be made available in the Destination table. Click Next.
   • In the Select Origin Fields for Table Copy wizard page, specify which fields from the origin table will be copied to the destination table. The check box at the top may be used to include or exclude all fields.
   • The message - The selected fields will be copied to the <table name> table upon completion of the Table Copy Operation, is displayed as a reminder of where the result of the copy operation can be seen. Click OK.
   • Enter a unique Identifier in the Specify Link or Operation Name wizard page.
   • The Completing Link Wizard page displays. Click Finish.
7. If you selected Perform Table Roll-Up:
   • The Select Table Roll-up Source wizard page displays. From the drop-down lists, select an Source Table and Source Key Field, and then type in a name for the Destination Table in the editbox. The destination table will be created, containing an aggregation of the source table over the source key field. Click Next.
   • In the Specify Aggregated Fields dialog box displayed, specify the fields to be included in the roll-up table and the operation type to apply to the field.

     To add a new aggregate field, click on the Add Field button. A new empty row will be added to the bottom of the list. Click on the Origin Field cell in the new row and select the field that you want to aggregate. Click on the Operation Type cell in the new row and select the operation type you wish to apply to the field. A default destination field name is placed in the last cell of the new row. If you wish to change this name, click in the Destination Name cell and type in the new name.

     For fields with numeric data types, operation choices include Copy, Count, Sum, Max, Min, and Avg. For categorical fields, operation choices are Copy and Count. The default operation for numeric fields is set to Sum, while categorical fields are set to use the Copy operation.

     You can delete any of aggregate fields from the list by highlighting the entire row by clicking on the box to the left of the first column. Shift and Control keys can be used to highlight multiple rows as once. Use the right mouse button to select the Delete Selected Rows context menu option.

     You can edit any of the existing aggregate fields clicking on the cell and either selecting a different value from the drop-down list for Origin Field and Operation Type columns, or by typing in a new name for the Destination Name column.

     Click Next.

   • Enter a unique Identifier in the Specify Link or Operation Name wizard page.
   • The Completing Link Wizard page displays. Click Finish.

For each type of link, there are also dialogs that allow existing links to be examined and modified. These dialogs use multiple tabs with essentially the same pages as exist in the Wizard.