Class H4WriterExperiment

java.lang.Object
  H4WriterExperiment

public class H4WriterExperiment
extends java.lang.Object

H4WriterExperiment - experiment software to test and demonstrate text input using Huffman coding.

If you are unfamiliar with H4-Writer begin by reading the first paper below.

Related references

The first paper below describes the rationale and specific details for designing text entry methods using Huffman coding. It also details the design and evaluation H4-Writer. The remaining papers describe extensions of H4-Writer to wearable computing, gesture input, and smart phones, respectively.

• 1 thumb, 4 buttons, 20 words per minute: Design and evaluation of H4-Writer, by MacKenzie, Soukoreff, and Helga (UIST 2011)

• Huffman base-4 text entry glove (H4-TEG), by Bajer, MacKenzie, and Baljko (ISWC 2012)

• Gestural text entry using Huffman codes, by Castellucci and MacKenzie (MHCI 2013)

• Eye on the message: Reducing attention demand for touch-based text entry, by MacKenzie and Castellucci (Journal of Virtual Worlds and Human-Computer Interaction, 2013)

Running the experiment software

Click here for instructions on launching/running the application.

Setup parameters

Upon launching, the application presents a setup dialog:

The default parameter settings are read from a configuration file called H4WriterExperiment.cfg. This file is created automatically when the application is launched for the first time. The default parameter settings may be changed through the setup dialog. The setup parameters are as follows:

• Participant code - identifies the current participant. This is used in forming the names for the output data files. Also, the sd2 output data file includes a column with the participant code.

• Condition code - an arbitrary code used to associate a test condition with this invocation. This parameter might be useful if the software is used in an experiment where a condition is not inherently part of the application (e.g., Gender → male, female, Input Device → gamepad, keyboard). The condition code is used in forming the name for the output data file. Also, the sd2 output data file contains a column with the condition code.

• Session code - identifies the session. Useful if testing proceeds over multiple sessions to gauge the progression of learning for H4-Writer.

  Note: The setup dialog does not include an entry for "Block code". The block code is generated automatically by the software.

• Number of phrases - specifies the number of phrases presented to the participant in the current block.

• Phrases file - specifies a file containing phrases of text to be presented to participants for entry. Phrases are drawn from the file at random. Typically, phrases2.txt is used. This is the phrase set published by MacKenzie and Soukoreff in 2003 (click here). The other files in the drop-down list are phrases2.txt, helloworld.txt, helloworld2.txt, quickbrownfox.txt, phrases.txt, phrases100.txt, vowells.txt, and alphabet.txt.

• Show presented text during input - a checkbox item that determines whether or not the presented text is visible during entry of a phrase. Either way, the text phrase appears at the beginning of a trial. If this option is unchecked, the phrase will disappear when the first keystroke is entered.

• Lowercase only - a checkbox item that, if checked, forces all letters in the presented text phrase to be lowercase.

• Show Huffman keyboard - a checkbox item that determines whether or not the Huffman keyboard is visible in the UI. It might be useful to uncheck this option if input uses an external keyboard and visual monitoring of the keys is to be avoided.

• Show symbols on keys - a checkbox item that determines whether or not symbols appear on the keys. Uncheck this option if input uses the mouse and visual monitoring of the letters on keys is to be avoided. This option is only relevant if the option above (Show Huffman keyboard) is checked. Note, as well, that this option only applies to the basic code tree (letters, period, comma, SPACE, BACKSPACE, ENTER, SYMBOL). If the user enters [symbol] to input a punctuation or special character, rendering of the symbols on keys is restored during entry of the symbol.

• Huffman code base - specifies the numeric base of the codes used in the Huffman code tree. The possibilities are base 2 through to base 10.

• H4Writer gamepad layout - a checkbox item that determines whether to use a gamepad-style layout for the keys. This option is only enabled if the option above (Huffman code base) is set to 4. If the code base is 4 and this option is checked, the keys are laid out similar the thumb-operated keys on the right side of a gamepad (see below).

Program operation

The program can work with Huffman codes in base 2 through to base 10. The number of keys is equal to the code base. The following are examples for base 2, base 4, and base 10: (click to enlarge)

The virtual keys are laid out, left to right, as many as needed. The left-most key is selected by pressing 1 on the system's keyboard. The next key is selected by pressing 2, and so on.

Mouse input is also supported. Just click on a key to select it.

There are two Huffman code trees for each code base, a basic tree containing the most common symbols and codes (e.g., letters, period, comma, SPACE, BACKSPACE, ENTER, SYMBOL), and a symbol tree for special symbols (e.g., digits, punctuation). Here are links to view the code trees:

Code base 2: h2.txt h2-sym.txt
Code base 3: h3.txt h3-sym.txt
Code base 4: h4.txt h4-sym.txt
Code base 5: h5.txt h5-sym.txt
Code base 6: h6.txt h6-sym.txt
Code base 7: h7.txt h7-sym.txt
Code base 8: h8.txt h8-sym.txt
Code base 9: h9.txt h9-sym.txt
Code base 10: h10.txt h10-sym.txt

In operation, entering "[symbol]" from the basic tree causes a transition to the symbol tree. The next selection is from the symbol tree. If the next selection is " [SymLock]" the symbol tree remains active for the input of multiple symbols, until " [SymLock]" is again selected.

The base-4 case — H4-Writer — is a configuration of particular interest. The GUI has a special look when the program is launched for 4-key input (if the option "H4Writer gamepad layout" is checked):

For this mode, it is intended that text will be entered with a four-key device, such as a gamepad:

Input will use the D-pad on a gamepad, with LEFT = 1, UP = 2, RIGHT = 3, and DOWN = 4. For the gamepad to work, software such as Xpadder must be installed and configured so that the gamepad keys generate the appropriate keystroke events on the host system. This is the mode of input used in the original paper presenting H4-Writer (click here to view).

As established in the original test of H4-Writer, users learn the codes after a few hours of practice. At this juncture, the rendering of the symbols on the keys is not needed. If the setup parameter "Show symbols on keys" is unchecked, the symbols do not appear. Here's an example for H4-Writer:

Output data files

At the end of each block, data are written to two "summary data" (sd) files. The "sd1" file contains data on a per-keystroke basis, one line per keystroke. The "sd2" file contains data on a per-phrase basis, one line per phrase. Example data files follow:

• sd1 example
• sd2 example

The data in the sd2 file are full-precision, comma-delimited. Importing into a spreadsheet application provides a convenient method to examine the data on a phrase-by-phrase basis. Here's how the data might look after importing into Microsoft Excel: (click to enlarge)

Actual output files use "H4WriterExperiment" as the base filename. This is followed by the participant code, the condition code, the session code, and the block code, for example, H4WriterExperiment-P01-C99-S07-B01.sd2.

Miscellaneous

During entry, a phrase may be aborted by pressing "r" ("restart") on the system's keyboard. This will terminate the current phrase and bring up a new phrase for input. "r" must be pressed before "Enter" ("LU" for H4-Writer) is entered. Data for the aborted phrase are not saved.

If "r" is pressed between phrases (i.e., after "Enter" is entered), the effect is to erase the newly-presented phrase and bring up a new phrase. Data for the previous phrase, which have already been written to disk, are not affected.

When using this program in an experiment, it is a good idea to terminate all other applications and disable the system's network connection. This will maintain the integrity of the data collected and ensure that the program runs without hesitations.

Author:

Scott MacKenzie, 2010-2014

Constructor Summary

H4WriterExperiment()

Method Summary

static void

main(java.lang.String[] args)

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

H4WriterExperiment

public H4WriterExperiment()

Method Detail

main

public static void main(java.lang.String[] args)
                 throws java.io.IOException

Throws:

java.io.IOException