- Main dialog:
The window at the top of the screen is referred to as the "main dialog." It is the
command center for the user interface (Figure 1). In the main window,
you can find the menu bar, the relation browser, the query browser, and the area on the
right to show the contents of relations and other dialogs. From the menus, you have
access to all the top-level dialogs in the user interface, such as the relation dialog
and query dialog.
As the CQA/CDB application gets started, relations and queries are loaded from
the corresponding repositories, containing all data that had been created in the
earlier sessions. After exiting the CQA/CDB system, the current database status
will be written to the repositories and is available for the next session.
Figure 1: main dialog of CDB
- Menu bar:
The menu bar is located on the top of the main dialog (Figure 1) and
provides the following items:
- File
- open (load a 'E00' file, a common file format in GIS, into the relation browser)
- properties (a checkbox menu item used to determine whether the
-tree
index should be used during query evaluation)
- exit (terminate the application)
- Relation
- create (create a new relation)
- delete (delete a selected relation)
- Query
- create (create a new query)
- delete (delete a selected query)
- run (run a selected query and save the result as a new relation)
- Relation Browser:
The Relation Browser is located in the left top of the main dialog below the menu bar
(Figure 1). It contains all the stored relations in a tree structure,
with a root node named 'Relation Schema.' The relation names appear in the first
level nodes and the attribute names belong to the second level. The handle of each
node may be clicked to show/hide its child nodes. The relation tables appear in the right
area of the main dialog as the relation names are clicked.
- Query Browser:
The Query Browser is located on the left bottom of the main dialog (Figure 1)
and it displays all stored queries in a list. A query consists of one or more
relational algebra operations. By double-clicking on a query item in the query browser,
the details of the query are shown in a query detail dialog containing all the operation steps.
- Relation Table:
By clicking on a relation name in the relation browser, the relation is shown a
s a table in the right of the main dialog. The table contains the structure and
the tuples of the relation. A button bar is located on the bottom of each relation table,
and may be used to switch to different views of the relation.
The attribute-view shows all of the attributes of the relation,
and the data-view lists all tuples of the relation
(see figures 2 and 3).
Figure 3: data view of the
land relation
Figure 2: attributes view of the
land relation
- Query Dialog:
The Query Dialog (Figure 4) is displayed when the
Query
Create menu items are chosen.
The operations implemented in the CQA/CDB system are placed as buttons
in the top area of the Query Dialog. The two windows on the left side of the Query Dialog
contain the available queries and relations in the corresponding repositories.
The window in the right of the query dialog (below the operation buttons)
contains the operation list that the user has entered.
Figure 4: query dialog of CDB
To add an operation into a query, the user clicks on a desired operation button,
and a corresponding Operation Dialog gets the focus (see section4.2).
The user may click the Ok-button of the Operation Dialog to return to the Query Dialog.
The operation then appears in the operation list, displaying the operation
name and its operands (e.g., "students join advising").
Several operations may be added to the list to form a complex query, and the last
operation produces the final result (see figures 19, 31).
The query may be stored by clicking the Save-button.
- Query Detail Dialog:
The Query Detail Dialog displays the operations of a query in a list.
Two buttons are below the list, namely, a Run-button to evaluate and store
the result of the query, and a Close-button to close the dialog.
The functionality of the Run-Button is identical to that in the Query Run Dialog.
Figure 5: Query Detail dialog of CDB
- Query Run Dialog:
The user may select the run item in the Query menu to start
the Query Run Dialog, which shows a list of available queries
and two buttons, i.e., the Close-button and the Run-button.
Select a query from the list and click the Run-button, the
Query Name Dialog appears, which may be used to save the query result as a relation.
Note that 'Save Query' check box in the Query Name Dialog is disabled.
Figure 6: Query Run dialog of CDB
- Query Name Dialog:
The Query Name Dialog (Figure 7)
gets started as a query or a query result needs to be saved.
The user may choose either one or both of checkboxes, namely, 'Save Query',
and 'Save Result Relation.' A textfield appears as a checkbox is chosen,
and the user is required to enter the name of the query or query result.
Figure 7: Query Name dialog of CDB
- Operation Dialogs:
Each operation implemented in the CQA/CDB system has a corresponding Operation Dialog.
A Operation Dialog has one or two pull-down lists to
choose the target relation(s) over which the operation is processed.
The Renaming, Selection and Projection Dialogs contain a table to edit
further parameters (see section 4.2).
