Propositional Production Systems

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Propositional Production Systems
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State Space

• State space The set of actions possible in a
  user interface, defined by a set of fields. In
  most cases the state space is partitioned into a
  set of controller state spaces, one controller
  per widget.
• Field Set of mutually exclusive conditions (or
  values). Each field is assigned one of its
  values. The collection of values gives the state
  of the system.

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Example Fields

• Two fields of a controller of a widget with their
  values listed in may be
• Color Black, White, Red
• Size Small, Medium, Large

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Input Events

• Widget controllers react to events performed by
  the user. These inputs are described by the
  Input field and additional fields to specify
  button states.
• The values of the Input field are events and are
  distinguished by a leading bullet h.

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Input Events (2)

• Input hMouseDown (one of the mouse buttons is
  pressed),
• hMouseUp (one of the mouse buttons is
  released),
• hMouseMove (mouse position is
  changed),
• hMouseEnter (mouse position enters a
  subwindow),
• hMouseExit (mouse position enters a
  subwindow),
• hKeypress (from keyboard)

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Input Events (3)

• Button state fields
• ShiftKey Shift, NoShift
• ControlKey Cntl, NoCntl
• LeftButton LeftDown, LeftUp
• MiddleButton MiddleDown, MiddleUp
• RightButton RightDown, RightUp
• and possibly others

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Exercises (1)

1. Why do we not use the simpler condition names of
   down and up for all the buttons?
2. Write the field values that represent discovering
   what an icon means by displaying its tag.
3. Write the field values that represent clicking on
   an OK button.

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Exercises (2)

1. Write the field values that represent dragging a
   folder on the desktop to the Recycle Bin.
2. What key fields are missing from the Input event
   definition?
3. Give the field values that represent choosing the
   File menu with the keystroke shortcut.

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Actions

• Widget controllers may have actions that they can
  perform. For example, a button controller for a
  Search button should, when pressed, invoke the
  search process.
• There may be more than one Action field if
  several actions can be carried out
  simultaneously.
• The values of an Action field are distinguished
  by a leading exclamation point ! .

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Actions (2)

• Examples
• FileAction !PrintFile, !DeleteFile,
• !CopyFile . Shows that one must choose only
  one of the three actions to perform.
• Action !Import

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Outside Events

• Frequently two widget controllers will want to
  communicate with one another.
• The values of a field describing an outside event
  are distinguished by a leading greater than sign
  gt showing information coming to a controller or
  by a trailing greater than sign gt showing
  information being sent to another controller.

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Outside Events (2)

• Examples
• EnDis gtEnable, gtDisable
• Shows that the widget controller accepts an
  outside message to enable or disable itself.

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Outside Events (3)

• Example A scroll bar needs to report its state
  to its parent window.
• TellParent Scrollgt, StepUpgt, StepDowngt,
  PageUpgt, PageDowngt

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Productions

• Productions are rules that show how the field
  values of the controller state space change.
• Productions are written in the form
• V1, V2,, Vp ? W1, W2,, Wq
• where Vi is the initial value (or condition) of
  a field and Wj is the resulting value of a field.
  Because all field values are required to have
  unique names, the field names do not appear in
  the productions.

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Productions (2)

• Example
• hMouseUp, Shift ? !DoMultipleSelect,
  InSelectMode
• says if the Input field has value hMouseUp and
  the ShiftKey field has value Shift, then set the
  Action field to !DoMultipleSelect (thus
  performing the action) and set another field to
  InSelectMode

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Simple Button

• A simple button is a window area that will invoke
  an action whenever hMouseUp occurs in the area.
• The controller state space for a simple button is
  defined by two fields
• Action !Import
• Input hMouseDown, hMouseUp, hMouseMove
  ,hMouseEnter, hMouseExit, hKeypress
• and one production
• hMouseUp ? !Import

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Button Fields

• Input
  
• LeftButton LeftUp, LeftDown
• VisualState Inactive, Active, Disabled
• Action !Extract
• DamageAction !DamageAll
• OutsideAction gtEnable, gtDisable

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Example

• Location Input LeftButton
• A MouseMove LeftUp
• B MouseEnter LeftUp
• C MouseDown LeftDown
• D MouseMove LeftDown
• E MouseUp LeftUp
• F MouseMove LeftUp
• G MouseExit LeftUp
• H MouseMove LeftUp

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Button Rules (Productions)

• 1. hMouseDown, LeftDown, Inactive ? Active,
  !DamageAll
• 2. hMouseUp, LeftUp, Active ? Inactive, !Extract,
  !DamageAll
• 3. gtDisable ? Disabled, !DamageAll
• 4. gtEnable, LeftDown ? Active, !DamageAll
• 5. gtEnable, LeftUp ? Inactive, !DamageAll

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Button Rules (2)

• 6. hMouseExit, Active ? Inactive, !DamageAll
• 7. hMouseEnter, LeftDown, Inactive ? Active,
  !DamageAll

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Button Exercises

1. Write the rules that describe the behavior of the
   Minimize button when it is pointed to.
2. Write the rules that describe the behavior of a
   button whose view does not change when it is
   pointed to.
3. Write the rules that describe the behavior of the
   Folders button in Windows Explorer when it is
   pointed to and the left mouse button is pressed.

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Button Exercises (2)

1. Write the rules that describe the behavior of the
   Folders button in Windows Explorer when the
   cursor is moved off the button while the left
   mouse button is pressed.
2. Write the rules that describe the behavior of the
   Folders button in Windows Explorer when it is
   pointed to and clicked.

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Query Fields

• A query field describes information the widget
  controller needs from the View. Each field
  represents one type of information, with one of
  several values. E.g., the following field checks
  the mouse location for a scroll bar.
• Mouse Location ?InSlider, ?InPageUp,
• ?InPageDown, ?InStepUp, ?InStepDown

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Query Fields Exercises

• Write a query field to work with a dialog box
  with drop down menu.
• Write a query field to work with a pane
  separator.

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Text Box Fields

• SelectionQuery ?SelectedPoint, ?SelectedRange
• SelectionAction !SetSelectStart, !SetSelectEnd,
  !OrderSelection
• State Inactive, Dragging
• KeyQuery ?DeleteKey, ?LeftArrow, ?RightArrow,
  ?NormalKey
• EditAction !DeleteSelectedRange,
  !DeletePreviousChar, !InsertChar,
  !DecrementSelection, !IncrementSelection

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Text Box Productions

1. -MouseDown, LeftDown, Inactive ? !GrabMouseFocus,
   !SetSelectStart, Dragging
2. -MouseMove, Dragging ? !SetSelectEnd
3. -MouseUp, LeftUp, Dragging ? !ReleaseMouseFocus,
   !SetSelectEnd, !OrderSelection, Inactive
4. -MouseDown, LeftDown, Inactive ? !GrabKeyFocus
5. -KeyPress, ?DeleteKey, ?SelectedRange ?
   !DeleteSelectedRange

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Text Box Productions

• 6. -KeyPress, ?DeleteKey, ?SelectedPoint ?
  !DeletePreviousChar
• 7. -KeyPress, ?LeftArrow ? !DecrementSelection
• 8. -KeyPress, ?RightArrow ? !IncrementSelection
• 9. -KeyPress, ?NormalKey, ?SelectedRange ?
  !DeletedSelectedRange, !InsertChar
• 10. -KeyPress, ?NormalKey, ?SelectedPoint ?
  !InsertChar

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Text Box Exercises (1)

1. Verify the productions (or change them as
   necessary) for the Named text box in the Find All
   Files window.
2. Verify the productions (or change them as
   necessary) for the text box that opens renaming a
   file in Windows Explorer.
3. Verify the productions (or change them as
   necessary) for the Location text box in Netscape.

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Text Box Exercises (2)

• 4. For Raskins design principles that describe
  interactions with text boxes, construct
  productions that codify these interactions.
• 5. For the course design principles that describe
  interactions with text boxes, construct
  productions that codify these interactions.

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Text Box Exercises (3)

• 6. Construct productions to describe the action
  that fills in a text box with a default character
  and leaves the character selected when one tabs
  to the next box.
• 7. Construct productions to describe the action
  that deselects a text string when either the
  right arrow or left arrow key is pressed.