The Main Screen

The first screen is the main user interface through which you may:

1. add sentences to, or remove sentences from, the knowledge base(s), the revision list, and the contraction list;
2. change the settings for the type of belief change, the search algorithm for equivalence sets, and the type of merging; and
3. carry out parallel change on a belief change scenario, and subsequently reject or commit a resultant knowledge base.

The selected knowledge base (KB) is the one whose index appears at the top of the drop-down list next to the "Add to KB" button on the main screen.
To add a sentence to the selected KB, you may:

• either type a sentence into the entry field and press the "Add to KB" button;
• or append to the selected KB an input file of sentences, by selecting from the menu "File" -> "Append to KB Selected";
• or replace the KB list with an input file of sentences, by selecting from the menu "File" -> "New KB...".

To add a sentence for revision, you may:

• either type a sentence into the entry field and press the "Add for Revision" button;
• or append to the revision list an input file of sentences, by selecting from the menu "File" -> "Append to Revisor";
• or replace the revision list with an input file of sentences, by selecting from the menu "File" -> "New Revisor...".

To add a sentence for contraction, you may:

• either type a sentence into the entry field and press the "Add for Contraction" button;
• or append to the contraction list an input file of sentences, by selecting from the menu "File" -> "Append to Contractor";
• or replace the contraction list with an input file of sentences, by selecting from the menu "File" -> "New Contractor...".

If a sentence being added has a syntactic error, the applet will display a red error message above the entry field and will not add the sentence.
Also, if the default consistency check is on and a sentence being added is either inconsistent or mutually inconsistent with the selected KB, the revision list, or the contraction list it is being added to, the applet will display a red error message above the entry field and will not add the sentence.

You may click the Default, CNF, and DNF buttons to view the sentences in a list in the default, CNF, and DNF format, respectively.

To remove a sentence from the selected KB, the revision list, or the contraction list, click the sentence and press the x button in the lower right hand corner of the corresponding list.
To erase the entire KB list, revision list, or contraction list, press the broom button in the lower right hand corner of the corresponding list. A dialog box with options Erase and Cancel will ask you to confirm the erasure.

To specify the settings for computing the belief change scenario, you may either use the "Settings" menu, or click the toggle buttons near the bottom of the main screen.
This bottom panel will also display informative messages and instructions where appropriate.

Here are the steps you should follow to carry out a belief change:

1. Once you have specified the settings and the belief change scenario you want to compute, press the "Get Parallel Change" button.
2. If there are inconsistencies in a knowledge base, the revision list, or the EB IC list, or if there are mutual inconsistencies between the revision list, the EB IC list, the contraction list, and the CB IC list, then a dialog box will notify you of all such inconsistencies.
   Until you resolve all such inconsistencies and press the "Get Parallel Change" button again, the belief change scenario will not be computed.
3. Preview the proposed resultant KB(s) in the New Knowledge Base Preview list.
   In the case of choice change, there may be more than one resultant KBs, each one listed on a separate line.
4. Either press either the "Reject" button if you wish to discard the proposed KB(s) and keep the current KB list,
   or choose a proposed KB by clicking it, and press the "Commit" button to replace the current KB list with the selected proposed KB.