Using the EG Applet

Bram van Heuveln

Contents

• General Comments– Some general comments regarding the use of

the applet

• Work Area– Instructions for creating and editing graphs

• Proof Area– Instructions for manipulating graphs in

accordance with the inference rules

General Comments

Proof Area and Work Area• The applet consists of 2 windows:

– Work Area: This is the area in which the user can create and edit graphs

– Proof Area: This is the area in which the user can manipulate graphs using the EG inference rules

General Comments

Canvas, Buttons, and Menu• Each window has 2 parts:

– Canvas: This is the big white area. This is where the graphs will be drawn.

– A Menu and Button Bar: A bar with menus and buttons containing operations that can be performed on the graphs on the canvas.

General Comments

Selecting an object• When operating on a graph, the user frequently has

to select part of the graph.• To select a proposition, click on the proposition• To select a cut, click at any place that is inside the

cut but outside of any other objects within that cut.• The selected object will become high-lighted.• The user frequently has to hold the mouse button

after selecting the object, and perform the operation before releasing the mouse button

General Comments

Overlap• None of the parts of a graph may overlap, as

this will form an ungrammatical expression. So, the applet is set up such that: – When the user tries to create a new object that

overlaps with an already existing one, then the new object will not be inserted.

– When the user tries to drag an object over another, the dragged object will be put back at its original location.

General Comments

Making Room• Because overlap is not allowed, the user

must always make sure that there is room for objects to be inserted, whether those objects are new or whether they are being dragged or copied from elsewhere.

General Comments

Operations• When the user wants to perform an operation, the

user has to select that operation from either the Menu Bar or the Button Bar (Buttons go fastest!).

• However, before performing any kind of operation, the user has to make sure that there is room for the operation to take place

• From now on, it is assumed that the user has made the appropriate choice of operation, and has made room for it to take place.

Work Area

Work Area: Creating and Editing Graphs• The Work Area is for creating and editing

graphs.

• Work Area contains the following operations:– Inserting new propositions or cuts– Moving propositions or cuts– Resizing cuts– Copying propositions or cuts– Deleting propositions or cuts

Work Area

Insert Proposition• To insert a simple proposition (e.g. ‘P’):

– 1. Click at the location where you want the proposition to be inserted

– 2. Type the letter you want to have inserted

• Note:– Simple propositions must be a single letter– A lower-case ‘a’ is seen as a different proposition

than a higher-case ‘A’!

Work Area

Insert Cut• To insert a cut:

– 1. Click at the desired location of one of the corners of the cut to be inserted

– 2. While holding the mouse button, move to the opposite corner (high-lighted cut should appear and move along)

• Note:– It doesn’t matter which corner you start with

Work Area

Drag 1• To drag or move a single cut or simple

proposition elsewhere:– 1. Select the object to be moved– 2. While holding the mouse button, move the

selected object to desired location

Work Area

Drag• To drag a cut together with all its contents:

– Like Drag 1

• Note:– Simple propositions can be moved with Drag as

well.– To drag all objects on the canvas, select any

place on the canvas outside all objects.

Work Area

Resize 1• To resize a single cut:

– 1. Select the cut to be resized, but make sure to click in the quadrant corresponding to the corner that will be moved (e.g. if you want to move the top-right corner, click somewhere in the top-right quadrant)

– 2. While holding the mouse button, move corner to desired location

Work Area

Resize• To resize a cut together with all its contents:

– Resize 1

• Note:– This operation does not work properly as of this

point: use with care!

Work Area

Copy 1• To copy a simple proposition or single cut:

– 1. Select the object to be copied– 2. While holding the mouse button, move copy

to desired location

Work Area

Copy• To copy a cut together with all its contents:

– Like Copy 1

• Note:– To make a copy of all objects on the canvas,

select any place on the canvas outside all objects.

Work Area

Delete 1• To delete a simple proposition or single cut:

– 1. Select object to be deleted

• Note: – To avoid the unintended deletion of the wrong

object, hold the mouse button before releasing it to see the selected object. If this is not the right object, move the mouse to change the selected object to the correct object.

Work Area

Delete• To delete a cut together with all its contents:

– Like delete 1

• Note: – Again, the user can hold the mouse button while

moving the mouse to make sure the right object gets deleted.

– To delete all objects on the canvas, select any place on the canvas outside of all objects.

Work Area

Move to Proof Area• To move graphs to be Proof Area:

– 1. Open the Proof Area window.– 2. Select the graphs from the Work Area you want

to move to the Proof Area (to select all, click anywhere on the Work Area canvas outside all objects).

– 3. Click anywhere on the canvas of the Proof Area– 4. While holding mouse button, move copy to

desired location.

Proof Area

Proof Area: Manipulating Graphs• The Proof Area is for manipulating Graphs

according to the EG inference rules.

• The Proof Area contains the following inference rule operations:– Insert/Erase Double Cut– Insertion and Erasure– Iteration and Deiteration

Proof Area

Illegal uses of Inference Rules• The applet checks to see if the user applies

the inference rules correctly.

• When the user makes an illegal use of an inference rule (e.g. the user tries to erase an object from an odd level), then the intended manipulation will not take place.

Proof Area

Editing• In the Proof Area, the user can still edit

(resize and drag) graphs, as long as the logical structure of the graph does not change.

• If the logical structure does change, then the operation will not be performed.

• Resizing and dragging serves 2 purposes:– to obtain a fresh perspective on a graph – to make room for other operations

Proof Area

Insert Double Cut• To insert a double cut around any subgraph:

– Like Insert Cut

• Note: – When drawing the double cut, only a single cut

will be shown. The second cut will be drawn inside this cut when the mouse button is released (be sure to leave some room).

Proof Area

Erase Double Cut• To erase a double cut:

– Click anywhere between the two cuts that make up the double cut.

• Note: – The user can hold the mouse button and move

the mouse to make sure the right double cut gets selected.

Proof Area

Insertion• To insert any graph on an odd level:

– 1. Create the graph to be inserted in the Work Area before selecting ‘Insertion’

– 2. Select the graph on the Work Area that needs to be inserted.

– 3. Click anywhere on the Proof Area (a copy will appear)

– 4. While holding the mouse button, move the copy to the desired location

Proof Area

Erasure• To erase any subgraph from an even level:

– Select the subgraph to be erased

• Note:– Hold the mouse button and move the mouse to

make sure the right subgraph gets erased.

Proof Area

Iteration• To iterate any subgraph on the same or any

nested level:– Like Copy

Proof Area

Deiteration• To deiterate a subgraph:

– Select the graph to be deiterated

• Note:– The applet will check if the selected subgraph is a

copy of another subgraph existing at the same or any nested level.

– Hold the mouse button and move the mouse to make sure the right subgraph gets deiterated.