1. Usability and operability 

1.1 The Two Definitions of Usability

The term “usability” is a critical attribute of the quality for an interaction IT product, and it has different definitions in two distinct standards. On the one hand, according to the ISO 9241-11 1998 -Guidance on Usability, “usability” means “the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of user”. （ISO 9241-11 1998 -Guidance on Usability）In other words, usability represents whether the product can completed the task for specified users, how users feel about the product, and how efficient the product is. Actually, usability is an important quality of a product from the users’ benefits.

1.可用性和可操作性 

1.1可用性的兩種定義 

術語“可用性”是質量為交互IT產品的一個重要屬性，并且它在兩個不同的標準，不同的定義。一方面，根據ISO的可用性9241-111998-指導，“可用性”是指“在何種程度上一個產品可以被指定的用戶來實現與有效性，效率和滿意度的指定的目標用戶“。 （關于可用性的ISO9241-111998-指南）換句話說，可用性指產品是否能完成任務，為指定的用戶，用戶的感受的產品，而該產品是多么的高效。實際上，可用性是一個產品的從用戶的利益的一個重要體現。

First of all, the meaning of the word “effectiveness” is the accuracy and integrity for the specified users when they achieve their specified goals. That is to say, a piece of software must be usable, can help the users to implement given goals. For instance, if the users can not achieve their goals by the software, no matter how easy and quick was the experience, it will not be effective. Secondly, “efficiency” in the definition is the ratio of the accuracy and integrity of the achievement to the resources which is used to achieve the specified goals.（ISO 9241-11 1998 -Guidance on Usability） For example, when a task execution takes “too much time” or need “so many clicking”, we will not say the software is efficiency. Thirdly, “satisfaction” in the explanation above means that the degree of comfortable and acceptable felt by the users during the utilizing of the product.

首先，單詞“有效性”的含義是指定用戶的準確性和完整性，當他們實現自己的特定目標。這就是說，一個軟件必須是可用的，可以幫助用戶實現特定的目標。舉例來說，如果用戶無法通過該軟件實現自己的目標，無論多么簡單而快速的是經驗，也不會是有效的。

On the other hand, the ISO/IEC 9126-1, 2001 defines the concept of “usability” as “the capability of the software product to be understood learned, used and attractive to the user, when used under specified conditions.”（Alain A. W. S., Adel K.J.R., Ahmed, Seffah & Francois R.） The usability represents the final quality of a product, and it decides whether the product is up to the users’ need under distinct environment by specified users. It includes three main ideas: “understandability”, “Learn ability” and “operability”.#p#分頁標題#e#

 

In the first place, understandability determines the ease of which the systems functions can be understood, relates to user mental models in Human Computer Interaction methods. An elegant programming in a piece of software should be easy to learn and understand. The users, for example, can easily know, what to do, where to click, and how do achieve their goals. Secondly, Learn ability means Learning effort for different users, such as novice, expert, casual etc. The software should be easily to learn whether by a first user or an expert, moreover it can support both a complex task and a simple one. The interface of the product ought to be attractive, besides it can bring satisfaction, interests and delight for the users. All the software can affect the emotion of users, a pleasant interface makes a user likes his work, meanwhile he will keep using this product. Otherwise, users may easily give up using the software with colorless interface. Finally, operability is “ability of the software to be easily operated by a given user in a given environment.” （ISO/IEC 9126-1, 2001）This definition concentrates on the easiness and specified of a task, it is a specific definition of “operability”.

Comparison of the two definitions

2.1 Usability in two different standards

According to numerous references I have found, an elegant piece of software must have a great deal excellent qualities. The definition from the ISO 9241-11 1998 - Guidance on Usability mainly focuses on the details about the users’ experience; it is more likely a narrow definition of usability. However, the definition of “usability” defined by the ISO/IEC 9126- 2001 is more comprehensive, and it is a broad concept that embrace all the ideas that mentioned in the standard---ISO 9241-11 1998 - Guidance on Usability. Besides, the definition from the standard---ISO/IEC 9126- 2001 concentrates on the users’ needs all the time in every sub-attribute.

 

Firstly, “effective” in the definition indicates that the specified users have mastered the main function of a piece of software, and don’t have to learn the software further. They can easily use the product to finish their specified goals. This item includes the sub-attributes of the definition in ISO/IEC 9126- 2001, if a piece of software has the capability to be “understood”, “learned” and “used”, that means the software can achieve users needs exactly, then we could draw the conclusion that the product is effective. For example, if a search engine, such as yahoo or Google, can quickly and easily help users to find what they want to know, like where is the nearest pizza restaurant, or how can I reach the Nation Theater, then users will consider the search engine is “efficient”, or it is or easily to be “understood”, “learned” and “used”. (Weiser M., 1984)#p#分頁標題#e#

Secondly, the item “satisfied” is a board description of the expectation that people hope a good IT product have. If a piece of software can not “attractive” to the specified users to utilize the product, it must not achieve the goals of specified users, and can not get appreciate from users. For instance, if a certain functions, such as the color of the interface, are unattractive, users may feel dissatisfactory with the system. As a result they will give up using the product. So the “satisfaction” can embrace the concept of “attractive”.

 

The last but not the least, “efficient” is a critical part of usability that can not be neglected. This characteristic is concerned about time; a piece of software ought to be time-saving when asked to achieve a specified goal. For instance, a piece of virus-killing software can achieve the goals, like scan the hard disc easily, quickly and correctly, the usability of this product is excellent. In conclusion, only a product can finish tasks given by users in the shorter time, can we say it is efficient? (Zuylen H., 1993) .The definition of “usability” defined by the ISO/IEC 9126- 2001 mentions the ability to be operated. If a product can be could be easy to operate, especially in a given circumstance, then we will say it is efficient.

3. Software Usability Measurement Inventory 

Questionnaire is used to collect the data and find out the opinion of the users about the software. There is a simple questionnaire, which might be used to help measure the usability of a piece of software. (http://xyza.edu.gatech/softmeas.html)

3.1 Sample as Follows: 

The questionnaire will give you an opportunity to tell your feelings of using the software. Your answer can help us to know your satisfaction or dissatisfaction about the product. So we can improve the design. Please recall all tasks you have done by the product when you answer the question, and choose the best answer which can express your feelings exactly.

Table1.  Questionnaire of Usability

Question about usability Agreement Scale

1

strongly agree 2

agree 3.

neither agree

nor disagree 4.

disagree 5.

strongly disagree

1. Generally I am satisfied with the easiness of the software.     #p#分頁標題#e#    

2. I can finish my job efficiently by the product.        

3. I can finish my job quickly by the product.        

4. I feel comfortable when using the product.        

5. It is easy to learn how to use the software.        

6. I think the software can help me to improve the productivity.        

7. The error tips given by the software can tell me clearly how to correct my mistake.        

8. If I make a mistake when I am using the software, I can easily and quickly come back.        

9. The software provide clear information (such as online help, information on the screen and the other files)#p#分頁標題#e#        

10. I can easily find information which I need.        

11. The information provided by the software is easy to understand.        

12. The information provided by the software is organized clearly.        

13. The interface of the software makes people feel cozy.        

14. I like the interface provided by the software.        

15. The software provides the functions I expected.        

16. This software responds too slowly to inputs.       #p#分頁標題#e#  

17. I would recommend this software to my colleagues.        

18. The instructions and prompts are helpful.        

19. The software has at some time stopped unexpectedly.        

20. Learning to operate this software initially is full of problems.        

21. I sometimes don't know what to do next with this software.        

22. I enjoy my sessions with this software.        

23. I find that the help information given by this software is not very useful        

24. I will never learn to use all that is offered in this software  #p#分頁標題#e#      

 

25. The software has helped me overcome any problems I have had in using it.        

26. The speed of this software is fast enough.        

27. I keep having to go back to look at the guides.        

28. It is obvious that user needs have been fully taken into consideration.          3.2 Instructions:

There are five degrees about each questions, you can only choose one answer for one question.

If you strongly agree with the question, you can choose 1.strongly agree.

If you agree with the question, you can choose 2.agree

If you do not agree or disagree with the question, you can choose 3.neither agree nor disagree.

If you disagree with the question, you can choose 4.disagree 

If you strongly disagree with the question, you can choose 5.strongly disagree.

 

3.3 Agreement Scale: 

1. Strongly agree

2. Agree 

3. Neither agrees nor disagrees  

4. Disagree 

5. Strongly disagree

(Uebersax JS. Likert scales: dispelling the confusion. 2006)

 

3.4 The Results:

There are 4 users’ (Jack, Julie, Susan and Mike) responds to the questionnaire.

Name The Number of answers#p#分頁標題#e#

1 strongly agree 2 agree 3 neither agree nor disagree   4 disagree 5strongly disagree

Jack 8 7 6 2 1

Julie 6 6 5 4 3

Susan 7 6 6 3 2

Mike 8 5 6 2 3  

From the inventory we can come to the conclusion that: all uses who attend the test are basically satisfied with the software. About the respects that can get the need of our users, we have to improve or add certain functions of the software according to the dissatisfaction reflected by four users. And in the future designing processes there are three basic aspects you should consider (Jones, P.Y, 1996):

Is your software quality better?

Is your software productivity better?

Is your company's time to market better?

4. The development of usability in the future

The ISO has developed a variety number of models to measure software usability, and each of the models has their flows. A challenge with definitions of usability is that it is very difficult to specify what its characteristics and its attributes should be, in particular because the nature of the characteristics and required attributes depend on the context in which the product is used. And still there are more characterizes should be taken into consideration to evaluate the usability. (Hainaut, J-L, Tonneau, C, Joris, M and Chandelon, M. 1993).

 

Firstly, the capability of comprehensive mistakes is necessary to measure software usability. This capability include that: the software can prevent users to make fault decisions, and also it can help the users to get back to the right operation from mistakes. For example, if a user clicks the wrong button accidentally, she/he may easily come back and find out what she/he really wants to do by the software. (Jackson, M.A. 1975)#p#分頁標題#e#

 

Secondly, the reaction speed of the system is another critical aspect of the usability. An unwritten rule has said that the specified users do not have to wait more than two seconds when they are in a certain circumstance. Such as when they start the program or switch the applications. That is to say, the shorter the time users wait, the better the users’ experiences are.  

References

 

Hainaut, J-L, Tonneau, C, Joris, M and Chandelon, M. (1993). Transformational Techniques for Database Reverse Engineering. Conference on Entity-Relationship Approach.

 

Jackson, M.A. (1975). Principles of Program Design. Academic Press, London.

 

Jones, P.Y (1996). Software Measurement: Case Studies of Twenty Organizations.

 

Weiser, M. (1984). Program Slicing. IEEE Transactions on Software Engineering, Vol. SE-10, No 4, July 1984, pp352-357.

 

Zuylen, H. (ed.) (1993). The REDO Compendium Reverse Engineering for Software Maintenance, John Wiley & Sons, Chichester.

 

http://xyza.edu.gatech/softmeas.html.

 http://www.400190.com/Engineering/

 

Alain A. W. S., Adel K.J.R., Ahmed, Seffah & Francois R. Consolidating the ISO Usability Models. Montreal, Canada. Retrieved April 20, 2008, from

http://www.lrgl.uqam.ca/publications/pdf/768.pdf

 

ISO/IEC9126(2001). Quality Characteristics and Guidelines for the User: Software Product Evaluation.   

 

ISO 9241-11(1998). Guidance on Usability

 

Uebersax JS. (2006). Likert scales: dispelling the confusion: Statistical Methods for Rater Agreement website. Retrieved April 20, 2008, from

http://ourworld.compuserve.com/homepages/jsuebersax/likert2.htm.