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INFSCI2470

Interactive System Design

Final Project

Disjunctive Normal Form (DNF)

Or

Conjunctive Normal Form (CNF) Educational Applet

Submitted By:

Polina Hristozova

Wei-chi Lin

Terry Nypaver

Todd Schryer

April 22, 2003

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Contents

1) Problem Statement ……………………………………………………………………..3

1.1) Meeting with client ……………………………………………………………… 3

1.2) Task-Centered Model …………………………………………………………… 3

2) Initial Draft Interface Design ……………………………………………….………… 5

2.1) Evaluation - Meeting with client ……………………………………………...… 5

3) Second Draft Interface Design …………………………………………………….… 6

3.1) Evaluation - Meeting with client ……………………………………………… 7

3.2) Enhancement – Rebuilt Task-Centered Model …………………………….… 8

4) Prototype System ……………………………………………………………………… 9

5) Non-User-Based Heuristic Evaluation – Usability Aspect Reports …………… 9

6) User Studies ………………………………………………………………………...… 16

6.1) On-line User Surveys ……………………………………………….………… 16

6.2) On-line User Survey Results ……………………………………………….… 20

7) Appendix – Expressions listed in the Applet ……………………………….…… 25

8) List of Figures ………………………………………………………………………… 27

9) List of Tables ………………………………………………………………………… 27

1) Problem Statement

1.1) Meeting with client

|First interview with our client. |

|Date: 03/18/03 |

|During our initial interview with our client, Dr. Peter Brusilovsky, we discussed the features and capabilities sought in |

|the educational applet. Specifically, the client is seeking an applet that will be utilized by undergraduate students to |

|learn about creating the Disjunctive Normal Form and Conjunctive Normal Form if provided with a truth table. The client |

|indicated that undergraduate students have historically found it difficult to understand the DNF and CNF forms. |

| |

|The client referred us to Information Storage and Retrieval by Robert R. Korfhage as reference information for the CNF and |

|DNF processes, and briefly reviewed the processes that the applet will ultimately illustrate. |

| |

|An educational applet has previously been authored that will illustrates the process of creating truth tables, and the |

|educational applet being sought at this time should operate in a parallel manner and simply extend the use of the truth |

|table to the DNF/CNF process. The client indicated that the educational applet should not be expected to be complex from a |

|programming standpoint, but instead should provide clear indications of the DNF and CNF forms. |

| |

|We discussed with the client the target users and their relative familiarity with the subjects of Disjunctive Normal Form |

|and Conjunctive Normal Form as well as potential access points to reach the target user’s, and it was mutually agreed that |

|such access may become a challenge. |

| |

1.2) Task-Centered Model

After learning about the proposed tasks and users, we listed our tasks as: teach the Conjunctive Normal Form (CNF), teach the Disjunctive Normal Form (DNF), and begin the authoring of the Help system. Then we discussed the selection of appropriate functions to present these tasks. We chose radio buttons for selecting the CNF/DNF form to prevent user errors, provided Step/Fly functions for use as a shortcut for experienced users, and text fields for users to limit input to ‘A’ and ‘B’ in each conjunct which will be joined by a drop-down menu containing ‘AND’ and ‘OR’. After users have input the proposed conjunct for the query, the input will be parsed and evaluated against the correct conjunct. Finally, we planned to provide a Solve button and Results field so that the user can check to see if the expressions that he entered are correct.

The task-centered model is depicted below, along with the actions required list:

[pic]

Figure 1: Task-Centered Model

2) Initial Draft Interface Design

[pic]

Figure 2: Initial Draft Interface Design

2.1) Evaluation - Meeting with client

After finishing the draft interface, we consulted with the client and sought his evaluation.

|Second interview with our client. |

|Date: 04/01/03 |

|We presented the first draft of the interface. It caused discussion and resulted in the following changes: |

| |

|1. We removed the partial expressions in the truth table. We discussed our concern regarding whether the truth table had |

|to be filled by the user. This appeared not to be part of the project requirements, and as a result the truth table will |

|be filled by the program. |

| |

|2. The number of variables in the expression will be three. We reached consensus that this is neither a small, nor a big |

|number, but sufficient for educational purpose. |

| |

|3. We changed the controls to represent the resulting CNF/DNF expression. Since this is the topic about which the applet |

|is teaching, we decided to use a set of controls that provide better interaction. Each symbol in the expression will have |

|a static position. Variables A, B, and C will be represented by labels. Before each variable there will be a drop-down |

|list with 2 elements only; ‘blank’ or ‘NOT’. Between two elements there will be a drop-down list with 2 elements: OR or |

|AND. In the space before the beginning of and in between every two expression lines there will be a drop-down list with |

|two elements OR or AND. At the end of each line there will be a Check button. |

| |

|4. We will provide a set of predetermined expressions, to avoid parsing of an infinite number of expressions. They will be|

|provided to the user in a drop-down list. |

| |

|5. We will keep the radio button CNF/DNF to let users choose what kind of expression they want to perform. |

| |

|6. As users fill the expression line, we will duplicate their entry in a text field at the bottom of the applet. This way |

|we can provide a single view of the whole expression. |

| |

|7. The applet will have two modes; ‘Teaching’ and ‘Trying’. We do not have a clear idea yet as to the set of buttons that |

|we will need to provide switching between the two modes. |

| |

|There will be definitely a Step Through button for the teaching mode. Each click of the button will fill one line of the |

|expression, resulting from the truth table, until all lines of the truth table are traversed. We will have a Fly button |

|to play the steps consecutively in a reasonable demo speed. In the Trying version the users will be left alone to fill |

|the expression. |

| |

|8. The applet will be started with parameter. Depending of the value of the parameter the applet will work in Teaching |

|only, Trying only or Both versions. |

3) Second Draft Interface Design

Following the enhancements, we created another draft interface as depicted below:

[pic] Figure 3: Second Draft Interface Design

3.1) Evaluation - Meeting with client

After implementing the interface enhancements, we arranged another interview with our client.

|Third interview with our client. |

|Date: 04/08/03 |

|On the third interview with our client we discussed the second version of the interface. We had to explain what the meaning |

|of each control on the form was. Walking through the interface was not enough - our client got confused. The interface |

|appeared to be very complex and clumsy. |

| |

|The problems included: |

|- a lot of interaction |

|- duplication of information |

|- waste of interface space |

|- difficult to get a feel of the whole expression at a glance |

| |

|In our opinion this design would help users to think while building the expression. But the client said that it would only |

|prevent the user from accomplishing their task easily. Our goal should be to provide a simple and easy-to-understand |

|interface. As a result the whole design of the expression filling area was rejected. |

| |

|We considered the idea of showing only one line at a time of the truth table, and respectively the expression filling area. |

|This was rejected because users would never be able to see the process of building the whole expression at once. |

| |

|Finally, we made the following decisions for the new design: |

|To provide the following controls after the Exp label on the line: |

|- AND/OR combo box for connecting the line expressions |

|- simple textbox for entering the line expression |

|- submit button to check the validity of the expression |

|- label to display the result of validation the expression |

|In addition, we will enumerate the lines of the truth table for easy reference. |

3.2) Enhancement - Rebuilt Task-Centered Model

Following the interview conclusion with client, we rebuilt the task-centered model as depicted below:

[pic] Figure 4: Revised Task-Centered Model

4) Prototype System

[pic] Figure 5: Prototype system

5) Non-User-Based Heuristic Evaluation – Usability Aspect Reports

I) Heuristic Evaluation

|HE 1 - Good Feature |

|Name |

|Order of controls |

|Evidence |

|Heuristic: Simple and natural dialog |

|The layout of the controls suggests the order in which the controls should be manipulated. |

|[pic] |

|Explanation |

|The location of the controls within the applet coincides with the order of operation, e.g., from left to right, and from |

|top to bottom. |

|Benefit |

|Users who are unfamiliar with DNF/CNF will be able to operate the applet. |

|Trade-offs |

|None evident. |

|HE 2 – Problem |

|Name |

|Enter answer textfields |

|Evidence |

|Heuristic: Prevent Errors, Minimize user memory load |

|User may not know how to input answer in correct format. |

| |

|[pic] |

|Explanation |

|The system may generate wrong message because of an incorrect character format even if the answer is correct. |

|Severity |

|Major – this may reduce the learning effect. |

|Possible Solution |

|Change textfield into select buttons to prevent error, or add help instructions to minimize user’s memory load. |

|HE 3 - Good Feature |

|Name |

|Symbols. |

|Evidence |

|Heuristic: Be Consistent |

|The symbols that the system uses and displays are all the same. |

| |

|[pic] |

| |

|[pic] |

|Explanation |

|The expressions that users input, the answers that the system generates, the symbols in the Help files, and the answers in|

|answer field all use the same symbols (&, v, and ~). |

|Benefit |

|User will not get confused by different symbols representing the same concept. |

|Trade-offs |

|Relationships |

|HE 4 – Good Feature |

|Name |

|Button hint. |

|Evidence |

|Heuristic: Speak the user’s language |

|User can understand what each button is intended to accomplish. |

|[pic] |

|Explanation |

|Each button function can be easily understood by its associated hint. |

|Benefit |

|Easy to manipulate the applet. |

|Trade-offs |

|None evident. |

|HE 5 - Good Feature |

|Name |

|Demo |

|Evidence |

|Heuristic: Minimize user memory load |

|When applet is first started it shows an example truth table and the corresponding expressions in DNF format. |

| |

|[pic] |

|Explanation |

|Since the truth table is always visible, it is a good idea to fill the first element of combo boxes with meaningful |

|expressions corresponding to the initial truth table values. |

|Benefit |

|Users can see immediately how the truth tale is used to construct DNF expressions |

|Trade-offs |

|None evident. |

|HE 6 - Good Feature |

|Name |

|Final Solution Textbox |

|Evidence |

|Heuristic: Provide feedback |

|The applet displays the combined expressions answer in the Final Solution textbox after the user has submitted their |

|responses or at the conclusion of the analysis of the expression. |

|Explanation |

|The Final Solution textbox is intended to provide users with a single area in which the correct DNF or CNF solution is |

|displayed. |

| |

|[pic] |

|Benefit |

|Users do not need to read the results from each line of variables in the Truth Table. |

|Trade-offs |

|Consumes interface space; users may not recognize that the information is identical to the information displayed on a |

|line-by-line basis. |

|HE 7 - Problem |

|Name |

|The Normal Form and the expression selected by the user do not appear in the Final Solution textbox. |

|Evidence |

|Heuristic: Provide feedback |

|The kind of Normal Form and the expression chosen by the user do not appear in the Final Solution textbox for the user’s |

|reference. |

|[pic] |

| |

|[pic] |

|Explanation |

|It is unclear what kind of Normal Form and which expression was chosen by the user when the user examines the final |

|answers. |

|Severity |

|Minor – user can review what he checked on the applet. |

|Possible Solution |

|Show the options that the user has selected in the Final Solution textbox. |

|HE 8 - Problem |

|Name |

|Symbol selection hint. |

|Evidence |

|Heuristic: Speak the users language |

|The symbol & / v may be not understood by a user. |

| |

|[pic] |

|Explanation |

|User may not know what these symbol mean. For example, they might learn that the term “and” is symbolized as “+” or “^” |

|instead of “&”. |

|Severity |

|Medium - occurs with new users. |

|Possible Solution |

|Change symbols into “AND (&) / OR (v)”. |

|HE 9 - Good Feature |

|Name |

|Reset function. |

|Evidence |

|Heuristic: Provide clearly marked exits |

|User can use RESET button to stop current expression. |

| |

|[pic] |

|Explanation |

|User may find that he has selected an expression that he previously learned. The User may also find he has selected the |

|wrong mode. The user can use the Reset function to exit the current setting immediately. |

|Benefit |

|Convenient method for the user to change his settings immediately. |

|Trade-offs |

|None evident |

|Relationships |

|HE 10 - Good Feature |

|Name |

|Fast Option |

|Evidence |

|Heuristic: Provide shortcuts |

|The Select Step has fast option which allows the user to see the rapid display of the CNF/DNF solutions. |

| |

|[pic] |

|Explanation |

|The fast option allows the user to quickly get an idea of how CNF/DNF works. |

|Benefit |

|Allows user to save time if desired. |

|Trade-offs |

|Beginning users may not find this feature appropriate. |

|Relationships |

|HE 11 - Good Feature |

|Name |

|Exit options from Help screens |

|Evidence |

|Heuristic: Provide clearly marked exits |

|Every Help screen has an option to immediately exit Help and return to the applet. |

| |

|[pic] |

|Explanation |

|Help screens have been constructed so that any Help can be exited directly to the applet in one click of the mouse |

|Benefit |

|Users can immediately return to utilizing the applet after browsing through needed help functions. |

|Trade-offs |

|None evident. |

|HE 12 - Good Feature |

|Name |

|Drop down menu for symbols. |

|Evidence |

|Heuristic: Prevent errors, Minimize user memory load |

|By using a drop down menu, the user can select the symbol and need not memorize symbols. |

| |

|[pic] |

|Explanation |

|Drop down menu facilitates the prevention of user input error, and also minimizes user memory load. |

|Benefit |

|The applet prevents input error and users who learn different type of symbols can easily identify them. |

|Trade-offs |

|None evident. |

Table 1: Heuristic Evaluation

II) Summary of Analysis

|Analysis ID |Heuristic |Good Feature |Problem |

|HE–1: Order of controls |Simple and natural dialog |X | |

|HE–2: Enter answer textfields |Prevent Errors | |X |

| |Minimize user memory load | | |

|HE–3: Symbols |Be Consistent |X | |

|HE–4: Button hint |Speak the user’s language |X | |

|HE–5 Demo |Minimize user memory load |X | |

|HE–6: Final Solution Textbox |Provide feedback |X | |

|HE–7: The NF and expression user selected |Provide feedback | |X |

|do not show up in the answer field. | | | |

|HE–8: Symbol selection hint. |Speak the users language | |X |

|HE–9: Reset function |Provide clearly marked exits |X | |

|HE–10: Fast Option |Provide shortcuts |X | |

|HE–11: Exit Options from Help Screens |Provide clearly marked exits |X | |

|HE–12: Drop down menu for symbols. |Prevent errors |X | |

| |Minimize user memory load | | |

Table 2: Summary of Analysis

6) User Studies

User studies were conducted to determine the effectiveness of both the applet’s advertised functionality as well as its interface. Initially a functioning servlet was developed to gather user responses, however technical challenges in loading the servlet to a publicly-accessible server led to the development of an HTML-based survey tool that collected responses through email using the “mailto” form action.

6.1) On-line User Surveys

The on-line survey posted for the evaluation of the applet and the collection of survey results was as depicted below:

Interactive System Design: CNF/DNF Applet Survey

By Polina Hristozova, Wei-chi Lin, Terry Nypaver and Todd Schryer

Please utilize this educational applet to learn about conjunctive normal functions and disjunctive normal functions, and then complete the survey below.

[pic]

Figure 6: Final Version Interface Design

Top of Form

In this survey, you will be asked about a variety of information technology questions concerning conjunctive normal function (CNF) and disjunctive normal function (DNF). One group of questions will inquire about your knowledge prior to using the educational applet, while another group of similar questions will inquire about your knowledge after using the educational applet. Additional questions will elicit information regarding your past educational history and experience with Information Systems. At the conclusion of the survey, you will be prompted to submit your responses by email.

|Prior to using the educational applet, please indicate your familiarity with the following terms: |

|Term |

|Term |

|Area |

|Item |

|Computing Area |

|Your History |No |Yes |I elect not to |

| | | |respond |

|Did you graduate from high school that used computers extensively? |[pic] |[pic] |[pic] |

|Are you a undergraduate college student? |[pic] |[pic] |[pic] |

|Are you in Information Sciences? |[pic] |[pic] |[pic] |

|Are you a graduate student? |[pic] |[pic] |[pic] |

|Have you ever been employed in your area of study (e.g., summer employment, co-op)?|[pic] |[pic] |[pic] |

|Do you own or have access to a computer at home? |[pic] |[pic] |[pic] |

|Please indicate what changes or improvements you would like to see in our next draft of the applet. |

|What appearance or layout features would you change? |[pic] | |

|Besides appearance or layout, what other changes would you |[pic] | |

|make? | | |

|What major problems did you encounter? |[pic] | |

Thank you for responding to our survey. Though we are not actually having a drawing, we would be interested in knowing what incentive would entice you to submit this survey. Please indicate which type of gift certificate would entice you to complete this survey and analyze our applet. Maybe in our next applet, we will actually give a prize out!

|Incentive |Select |

|CD Store |[pic] |

|Pitt Book Store |[pic] |

|Phone Card |[pic] |

|Barnes & Noble |[pic] |

|Gas Card |[pic] |

|Food Card |[pic] |

|I would not want any gift certificate |[pic] |

|I elect not to respond |[pic] |

|[pic] |[pic] |

Table 3: On-line User Survey

Bottom of Form

6.2) On-line User Survey Results

We only received a handful of survey back to us. In our discussions with some potential users, most of them had difficulty displaying the applet. They were able to see the survey. One person mentioned that he “thought something was wrong because the Applet was not showing up.”   Then he talked with his Network administrator. The administrator stated “he has applets blocked from showing up.”  So, he was unable to test it. Another wrote “I'm confused - the url gets me to the survey, but I can't see how to start the applet.”  When we mentioned about downloading from Java, he followed with “I'm striking out - I already have the latest Java for Mac OS 9.2 according to the site.” Another stated “I'm not sure if I missed something or not, there was no educational applet or at least it didn't open. The survey was there, but would be useless without reviewing the applet.”

When we tested it with several people in the office, we had to go to each system and download software from before the applet would appear. In fact, nearly everyone who attempted to use our appeared to have this problem. We used the latest version of JDK software for our work, but did not consider how this would affect other systems from running the applet because they didn’t have the latest java software. Initially, they all were able to see the survey, but not the applet.

Survey Use

We cannot come up with any conclusions with the surveys results we received because of the number of surveys actually received and those surveys meeting our target audience. We will only record the summary of the surveys.

The users understood the following items after first use: Step/Fast, Solve/Submit, SeeCorrectAnswer, and GetHelp

The users understood the following after the first use or after some use: SelectionProcess, Teach/Learn, SubmitEntries, and CorrectEntries

The users understood the following after some use : EnterAnswer

The users were very satisfied with: DataEntry and Help.

The users were very satisfied or somewhat satisfied with: Appearance/Format and Consistency

The users knowledge of widgets varied as it depended on the knowledge about computers and programming languages

So the results indicate that help and date entry were clearly defined.

Survey Suggestions

We received a suggestion to place the solve button could be at the bottom. We would have to this under advisement.

On Help

Help was a great tool. One person stated “when I first was able to see the applet, I was confused on exactly what it was to be used for...until I saw the Help button near the bottom. I have heard of those terms used in logic (since I took logic classes myself) but since I never use them in real life, I had forgotten what the abbreviations meant. That was a bit confusing at first but the Help was really good. “ Another had a problem in that the help window did not fit into her screen display, so that she was lost as to how to get out of it. She rebooted, figuring her system locked up.

Testing Human Reaction

Our target users are the undergraduate Information Sciences students and our clients are their instructors. Since we could not get a face to face study for the testing, we decided to perform a test with the people in the office. These people are not undergraduate Information Sciences students, however they do work with a database system via interface screen. We used them to test their reaction. In observing those in the office, we did discover a couple of important human factors we did not consider. One person was confused (and rightfully so) as to what to do, so she kept moving her mouse in circles while trying to figure out what to do. This never gave her the opportunity to see the tool tips over any entry points. Another scrolled up and down the entire page, so once she past the applet, all she could see was the survey. She was scanning to find something that attracted her attention.

The mood of the user should be taken into account at the time of use. One user was frustrated all day, so when approached about the applet, she could care less about it. The mood will definitely affect the users interest.

Another could see some of the data entry points, but it wasn’t very obvious as to their purpose. Since the truth table, titles, labels and data entry points all had the same background and foreground colors, they blended in together. This made it difficult to see where they need to concentrate on.

Emailing the survey

Emailing the form was another problem. One person stated he had a problem since the “survey has to be submitted via email...when I was using Netscape Navigator 7 to view the site and complete the survey, it prompted me to use an AOL email or Netscape email account...I do not use either. My survey could not be submitted due to the restrictions of the browser (it would not let me use my configured Outlook Exchange account).” We had worked on a servlet to tally the results, but then realized we did not have access to a server that would allow us to do that. So we were forced to use email, which created this problem.

Improvements And Suggestions For The Applet

We implemented several improvements in our final version. We color- coded the answers, so if the user made the correct entry, the answer appeared in green. If the user made an incorrect entry, the answer appeared in red. We also color-coded the results of the expression to make it obvious in the truth table.

We added an undo button to clear out the last line. So the user can go back to the previous line and try again.

We allowed the client / teacher three parameters they can change in the applet. One is the learn only parameter (which must be set to “Learn”) to disable the teach mode. This will allow the user to operate in the learn mode only, forcing he to check his answers. The other two parameters are the fast and slow delay times while solving the problems.

The major improvement of this applet which we must do is to make the applet and html file work across all systems (Unix, Windows, Mac) and with all of the different browsers. One feedback stated “Applet does not function in Internet Explorer 6 with SP1.” We also must consider what affect the display settings have on the appearance of the applet.

We should change the statement just above the applet and make the applet appear it the first screen without the need to scroll down. Currently, the statement only mentions the purpose, so it would be beneficial for us to change the text to refer to the help in a statement or two. We probably should not use the term ‘applet’ until it becomes more commonplace.

By making the applet appear in one screen will prevent the user from having to scroll immediately to see the applet, thus avoiding the tendency to scroll beyond the applet. A suggestion may be to have the survey on a different page, with a button to indicate to go to the next page. That would force the user to try the applet before submitting the survey.

We probably should avoid the word ‘survey’ in the text, because some people have the tendency to bypass them if they require any work. If we want feedback, we should say that there is an incentive to filling the survey out, like being place in a drawing for a prize if you spend the fill the survey out. In our version, we only asked what you would like to receive, and didn’t give anything away.

Finally, we could add parameters to allow the instructor to change the colors of the displays, in case he prefers a different color, or if the person is color blind.

8) Appendix – Expressions listed in the Applet

| | | | | | | | | | |

|Expression 1 : (A&B) v C |

|A |B |C |A&B |C |Expr |DNF |CNF |

|T |T |T |T |T |T |　 |A&B&C |　 |　 |

|T |T |F |T |F |T |v |A&B&~C |　 |　 |

|T |F |T |F |T |T |v |A&~B&C |　 |　 |

|T |F |F |F |F |F |　 | |　 |~AvBvC |

|F |T |T |F |T |T |v |~A&B&C |　 |　 |

|F |T |F |F |F |F |　 | |& |Av~BvC |

|F |F |T |F |T |T |v |~A&~B&C |　 |　 |

|F |F |F |F |F |F |　 |　 |& |AvBvC |

| | | | | | | | |　 | |

|Expression 2 : (A&B) v (B&C) |

|A |B |C |A&B |B&C |Expr |DNF |CNF |

|T |T |T |T |T |T |　 |A&B&C |　 |　 |

|T |T |F |T |F |T |v |A&B&~C |　 |　 |

|T |F |T |F |F |F |　 | |　 |~AvBv~C |

|T |F |F |F |F |F |　 | |& |~AvBvC |

|F |T |T |F |T |T |v |~A&B&C |　 |　 |

|F |T |F |F |F |F |　 | |& |Av~BvC |

|F |F |T |F |F |F |　 | |& |AvBv~C |

|F |F |F |F |F |F |　 |　 |& |AvBvC |

| | | | | | | | | | |

|Expression 3 :(A&~B) v (B&C) |

|A |B |C |A&~B |B&C |Expr |DNF |CNF |

|T |T |T |F |T |T |　 |A&B&C |　 |　 |

|T |T |F |F |F |F |　 | |　 |~Av~BvC |

|T |F |T |T |F |T |v |A&~B&C |　 |　 |

|T |F |F |T |F |T |v |A&~B&~C |　 |　 |

|F |T |T |F |T |T |v |~A&B&C |　 |　 |

|F |T |F |F |F |F |　 | |& |Av~BvC |

|F |F |T |F |F |F |　 | |& |AvBv~C |

|F |F |F |F |F |F |　 |　 |& |AvBvC |

| | | | | | | | | | |

| | | | | | | | | | |

| | | | | | | | | | |

| | | | | | | | | | |

|Expression 4 : (A&~B) v (B&~C) |

|A |B |C |A&~B |B&~C |Expr |DNF |CNF |

|T |T |T |F |F |F |　 | |　 |~Av~Bv~C |

|T |T |F |F |T |T |　 |A&B&~C |　 |　 |

|T |F |T |T |F |T |v |A&~B&C |　 |　 |

|T |F |F |T |F |T |v |A&~B&~C |　 |　 |

|F |T |T |F |F |F |　 | |& |Av~Bv~C |

|F |T |F |F |T |T |v |~A&B&~C |　 |　 |

|F |F |T |F |F |F |　 | |& |AvBv~C |

|F |F |F |F |F |F |　 |　 |& |AvBvC |

| | | | | | | | | | |

|Expression 5 : (~A&~B) v (B&~C) |

|A |B |C |~A&~B |B&~C |Expr |DNF |CNF |

|T |T |T |F |F |F |　 | |　 |~Av~Bv~C |

|T |T |F |F |T |T |　 |A&B&~C |　 |　 |

|T |F |T |F |F |F |　 | |& |~AvBv~C |

|T |F |F |F |F |F |　 | |& |~AvBvC |

|F |T |T |F |F |F |　 | |& |Av~Bv~C |

|F |T |F |F |T |T |v |~A&B&~C |　 |　 |

|F |F |T |T |F |T |v |~A&~B&C |　 |　 |

|F |F |F |T |F |T |v |~A&~B&~C |　 |　 |

| | | | | | | | | | |

|Expression 6 : (~A&~B) v (~B&~C) |

|A |B |C |~A&~B |~B&~C |Expr |DNF |CNF |

|T |T |T |F |F |F |　 | |　 |~Av~Bv~C |

|T |T |F |F |F |F |　 | |& |~Av~BvC |

|T |F |T |F |F |F |　 | |& |~AvBv~C |

|T |F |F |F |T |T |　 |A&~B&~C |　 |　 |

|F |T |T |F |F |F |　 | |& |Av~Bv~C |

|F |T |F |F |F |F |　 | |& |Av~BvC |

|F |F |T |T |F |T |v |~A&~B&C |　 |　 |

|F |F |F |T |T |T |v |~A&~B&~C |　 |　 |

Table 4: Expressions list

9) List of Figures

Figure 1: Task-Centered Model …………………………………………………………… 4

Figure 2: Initial Draft Interface Design ……………………………….…………………… 5

Figure 3: Second Draft Interface Design ………………………………………………… 6

Figure 4: Revised Task-Centered Model ………………………………………………… 8

Figure 5: Prototype system …………………………………………………..…………… 9

Figure 6: Final Version Interface Design ………………………………………..……… 16

10) List of Tables

Table 1: Heuristic Evaluation …………………………………………..……………… 9-15

Table 2: Summary of Analysis …………………………………………………………… 15

Table 3: On-line User Survey ………………………………………………….………… 20

Table 4: Expressions List ………………………………………………………………… 26

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