Usability evaluation of an e-Service in a Public website

OREBRO UNIVERSITY SWEDISH BUSINESS SCHOOL

INFORMATICS

Usability evaluation of

an e-Service in a Public

website

Project work 2010

vijaypaidi@yahoo.co.in Supervisor Hannu Larson Examinator Anders Avdic Date 22/4/2010

I

Abstract

Enough research was not done in evaluating a public website which would provide e-services to all kinds of citizens. A public website would provide e-services to all kinds of people and also provides the services faster and easier with fewer errors, so it is necessary to provide a usable website to the users. So usability evaluation of an online payment service in a public website is described in this paper.

Usability evaluation has been carried out by performing heuristic evaluation which is a usability inspection method and interview which is a usability testing method. A conceptual framework was developed to identify the nature of reality and data matrixes were used to present the data gathered, by performing the methods.

The usability evaluation performed by heuristic evaluation and interviews had identified usability problems from both non-user and user point of view. Using both the methods, more number of usability problems were identified which are necessary for the improvement of online payment service in a public website.

II

Acknowledgement

I would like to thank the users of website who participated in the interviews, evaluators who performed heuristic evaluation to find usability problems in the website and my supervisor who guided me in writing the paper.

1

Introduction

Usability as defined by ISO/IEC 9241 standard is “the extent to which the product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use”. As the usage of web has increased worldwide, it is important to maintain the usability characteristics of a website (Liu, 2008).

A public website would provide e-services to all kinds of people and also provides the services faster and easier with fewer errors, so it is necessary to provide a usable website to the users (Lili, Stuart, & Jon, 2005).

E-seva is one of the e-governance initiatives taken by the government of Andhra Pradesh in India; the main theme of e-seva is to provide a one-stop venue for various services by the use of Information Communication Technologies (ICT’s). It provides different services through computerized Integrated Citizen Service Centres (ICSC’s). These centres are located in different parts of the state. Internet services are also provided by e-seva and these internet services comprises of online payment, downloading of forms, government orders and online filling of applications on the web. (Prabhu, 2004) These online services are only provided in Hyderabad, which is the capital city of the state and they are provided through (esevaonline, 2001) which is a public website.

Online transactions and online services are one of the important stages in developing e-government. This change the way people interact with their government, it saves time and money for public and government. (Layne & Lee, 2001) E-Government is the use of ICT’s to improve public services and democratic processes (EU, 2004). So the usability evaluation of online payment service of e-seva is evaluated in this paper.

1.1 Objective and research question

The objective is to evaluate the usability of online payment service in a public website. The public website referred to is the e-seva website. The main research question is: How is the usability of an online payment service in a public website?

1.2 Operationalization of research question

 How is the usability evaluation using an inspection method  How is the usability evaluation using a testing method  How to identify different usability problems

1.3 Literature review

There has been previous research done in this field, but most of the research is done in the private sector rather than the public sector. Usually the investment on a web-based e-government service would be enormous and the services provided by the e-government would be used by all the citizens. Despite the importance of the public e-services little research has been done in this field. (Lili, Stuart, & Jon, 2005)

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As a public website would provide services to users with different gender, age, education, career, income, literacy, etc, the website should follow some criteria and it should be usable to all kinds of users. (Lili, Stuart, & Jon, 2005)

Usability evaluation was performed by Heuristic evaluation in many papers as this is widely used and the most efficient one (Otaiza, Rusu, & Silvana, 2010). If a usability evaluation is carried out by relying on any single evaluation method, it will be misleading and incomplete. A multidimensional web evaluation strategy can be used to successfully evaluate web-based e-government service. The usage of several web evaluation methods will achieve multidimensional web evaluation (Wood, et al., 2003). So in this paper, usability evaluation is carried out by using one of the usability inspection methods and one of the usability testing methods.

The literature search was carried out using online databases like ACM digital library, IEEE explorer and Google Scholar. Keywords like usability, usability evaluation and different synonyms of the keywords were used to search for the literature. The title and abstract was checked for every article and if the title or abstract fits the purpose of the paper then it is kept aside for further reading of the article. The method and conclusion were checked for the articles which are kept aside in order to have a better understanding about usability evaluation. In this way the literature search was carried out to find related articles about previous research done in this field.

1.4 Delimitation

The online payment service is one of the e-service provided by the public website and this would be used by the whole population of the city, but the results of the study will only reflect the views of the sample size involved and not the views of whole population.

1.5 Outline of the paper

The method section provides how heuristic evaluation and interviews have been carried out. The result section presents the data gathered from interviews and heuristic evaluation. The analysis presents the problems into two categories which are major and minor. The conclusion presents the summary of the usability evaluation and the discussion presents about any patterns identified in the paper.

Method

Usability evaluation is defined as “systematical process of collecting data, in order to have a better understanding of users and how user groups use the product to perform a specific task under specified conditions” (Sharp, Rogers, & Preece, 2007). Performing usability evaluation will help in improving the websites on basis of users demand and would meet the need of users (Liu, 2008). Usability evaluation methods are commonly divided into usability inspection method and usability testing method which is described in detail in further sections. (Otaiza, Rusu, & Silvana, 2010)

3 2.1 Usability Inspection method

This method evaluates usability of a system by inspection. The inspection is carried out by usability evaluators who identify problems in the design. There are different usability inspection methods where heuristic evaluation is one among them and is efficient in finding the usability problems. So, heuristic evaluation was chosen as one of the method for finding usability problems in the paper (Otaiza, Rusu, & Silvana, 2010). This evaluation was conducted using the ten usability heuristics developed by (Nielsen J. , Heuristic Evaluation, 2005).

2.2 Usability Testing Method

Usability testing identifies the usability problems by performing empirical testing of the system with representative users, (Otaiza, Rusu, & Silvana, 2010) in this case the representative users are the citizens who are the users of online payment service. There are several testing methods, but interviews were chosen for gathering the empirical data in this paper. Performing interviews is cheap and simple and it gives the usability problems actually faced by the users of the e-service.

2.3 Conceptual Framework

Two usability evaluation methods have been chosen to perform the usability evaluation in this study. (Otaiza, Rusu, & Silvana, 2010) The usability evaluation was carried out for one e-service of the website to be more specific in finding the problems rather than involving all the services provided by the website.

The conceptual framework which is shown in figure.1 has been originally derived from (Otaiza, Rusu, & Silvana, 2010). The framework was then modified according to the need of the paper. The process of usability evaluation has been taken from (Otaiza, Rusu, & Silvana, 2010) and this is applied to an e-service of a public website in this paper. A public website provides online services and online payment is one of the e-services provided by the public website. This online payment process undergoes usability evaluation and this is performed by heuristic evaluation which is a usability inspection method and interviews which is a usability testing method. Performing both the methods help in identifying usability problems and these problems can be provided as a feedback for the designers, which can be used for further improvement of the website (Nielsen, Overgaard, Pedersen, & Stage, 2005).

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Public Website Online Services

Online Payment Usability Evaluation Usability Inspection Method Usability Testing Heuristic Evaluation Interviews Usability Problems Feedback for Designers provides consists undergoes performs performs uses uses Identifies Identifies provides Figure.1Conceptual Framework 2.4 Collection of data

Data has been collected by performing heuristic evaluation which is a usability inspection method. Heuristic evaluation works better with at least three evaluators, which is the reason why three evaluators were chosen for this study (Nielsen J. , 2005).

The evaluation was performed by evaluators who have a computer background education and have completed their graduation. These evaluators are not considered experts in usability evaluation but have some experience in finding out usability problems by performing heuristic evaluation. They have been given access to the online payment service by providing the login information as they were not the actual users of the website.

Heuristic evaluation was performed by these evaluators independently, using the ten usability heuristics which can be found in Appendix-B and different usability problems were noted down. Textual data is gathered from the evaluators and then the author registered the data in a separate document for further interpretation.

Data was also collected by performing interviews which is a usability testing method. The interview questions were derived from the usability heuristics and modified according to user’s language. Semi structured interviews were conducted for this study in order to ask any additional questions according to user’s response (Oates, 2006) and these questions are only related to user’s perceptions about the interface design of the website. The interviews were carried out using online phone, field notes were taken during interview and the conversation was recorded using voice recorder. There were total 8 interviews which were done, but only 7 interviews were recorded as a technical error occurred during one interview. It was hard to avoid technical error, but as field notes were taken during the interview, the data was not completely lost. This error occurred while recording the conversation with interviewee 4, so the data noted in the field notes was interpreted and presented in the results.

The interviewees selected for this study were from different backgrounds and occupation, and they were selected using convenience approach. The interviewees were users of the public website and are familiar with internet and online services.

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The interviewees were asked prior the interview that the conversation would be recorded and it was recorded only with the permission of the interviewee. The recorded data was then transcribed and registered in the form of textual data which makes it easy for further interpretation. The time taken for the interview was also informed prior to the interviewee. The anonymity of the interviewees was maintained and the registered data was kept confidential. (Oates, 2006)

2.5 Analysis

The data matrix is used as an instrument for the analysis of the collected data. The idea of data matrix has been derived from (Oates, 2006), which is used for analyzing qualitative data. The transcribed data is interpreted and presented in the data matrix for analysis. The data collected from heuristic evaluation and interviews was presented in two different data matrixes. The data matrix which is used to present the interview data is shown in Table.1, it consists of elements as the interview questions and these questions are represented as codes in the data matrix. These codes are presented against the interviewees and the data gathered from each interview is presented under different interviewees. The interview questions and the codes representing the interview questions can be found in Appendix-A.

The data matrix used for presenting the data gathered from heuristic evaluation is shown in Table.2. This data matrix consists of elements as usability heuristics derived from (Nielsen J. , Heuristic Evaluation, 2005) and the data is presented against different evaluators. The usability problems identified are presented under each evaluator against different usability heuristics.

The data presented in the results is analyzed into two categories which are major and minor. A usability problem is considered major if they have serious potential for confusing users or causing them to erroneous use of the system, (for example if a user can’t reset the changes he made during a process and there is no emergency exit then this would cause loss of information and user strain, which is a major problem) while minor problems are those which slow down the system interaction unnecessarily (Nielsen J. , 1992) (for example, irrelevant information in the website makes difficult for the user to find what he/she needs and slowdowns the user actions, which is a minor problem )

Result & Analysis

The interpreted data from the analysis of the transcribed data is presented in Table 1. The interpretation was done in order to identify the usability problems from the transcribed data. The data gathered by performing heuristic evaluation by 3 evaluators is registered as textual data and this data has been interpreted to identify the usability problems in the textual data. This interpreted data has been presented in Table.2.

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Table.1 Interview data

Elements Interviewee#1 Interviewee#2 Interviewee#3 Interviewee#4 Interviewee#5 Interviewee#6 Interviewee#7 Interviewee#8

[A] -Accountant -Not a regular user of internet Undergraduat e student -Regular user -Software employee -Regular user -Software employee -Regular user -Undergraduate Student -Regular User -Jr.Engineer - Regular User -Software employee -Regular user Undergraduat e Student -Regular user [B]

-It is ok -Not clear -No hierarchical design

-It is clear - Alignment of data can be improved

-It is clear -No clear information

-No problem -No clear information [C] -Haven’t faced any problems -Not clear(mixture of languages)

-No problem -Font size can be increased -Easy to understand -Language is understandable -It is easy to understand -It is more technical, difficult to understand [D] -No Back option and the home button is annoying -No back option, No emergency exit. Cannot reset changes -Home button is problematic -Home button is problematic -No back option, home button is problematic -No back option, home button is problematic -Navigation is difficult in some pages, home button is problematic during navigation -No emergency exit in every page -Cannot undo and redo changes -Home button is problematic as it logouts the user [E]

-No problem -Tabs in homepage are confusing -Clear Information -No proper information of the bill

-No problem -Inconsistent wording in home page among tabs, few data unclear in registration

-No problem -It is not user friendly [F] -No User confirmation procedures -Technical errors during payment -No error prevention -No error prevention -No proper password recovery option -No user confirmation during payment process

-No errors -No errors -No errors -No error prevention -Cannot reset changes made during payment process [G] -Actions are easy to perform -Problem in navigation, not user friendly -Easy to use no need to remember -Can increase the user friendliness of the website -Easy to use, no need to remember -Easy to operate -No need to remember anything -It is easy to use, no need to remember [H]

-No problem -Works well with only internet explorer, problem with choosing pop down menu

-No problem -No automatic payment -Cannot pay multiple bills at a time -Should check the bank statement every time

-It is efficient -Difficulty with pop down menu in homepage -Can include more banks, can increase services -It is ok but can improve more banks for online payments -Selection of areas is confusing and navigation is little hard [I] -Information is aligned properly -Contains irrelevant information and is better to divide the payment process

-No problem -Not much irrelevant information

-Have irrelevant information in the home page

-Little irrelevant information

-No problem -Redundant information is provided in the home page which is confusing [J] -No recover of errors during transaction -It doesn’t help to recover errors rather gives error number -No errors faced till now

-Haven’t faced any errors for recovery -No errors faced -No errors faced till now

-No errors faced till now

-No errors faced till now

[K]

-Did not find any help section -No help provided -No help provided -No proper help section except a demo -No help provided -No help provided -No help provided -No help section provided

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Table.2 Data from Heuristic evaluation

Elements Evaluator#1 Evaluator#2 Evaluator#3

Visibility of system status

-No feedback within reasonable time during the web process

-The system status is mentioned during the navigation of the website

-No proper feedback of the website -No proper alignment of data

Match between System and real

world

-The website uses acronyms which might not be understandable for everyone

-The language is easy but in some cases has a mixture of languages which might be confusing

-The language uses acronyms which might not be easily understood -Font size can be increased

User Control and freedom

-The system does not support undo or redo changes

-The home button makes the usage of the website problematic

-Not completely user friendly

-Lack of undo and redo changes -No emergency exit

-Home button is problematic for navigation as it makes the user logout

-No emergency exit -No undo redo changes -Pressing home button makes the user logout

Consistency and standards

-It does not provide information about the services

-The structure and layout is not coherent

-The website can be more informative about the services provided

-Similar words which confuses the user in the homepage

-No proper information of the bill

Error prevention

-Does not prevent errors during payment process

-Should always check the bank statement for the confirmation of payment

-It can lead to errors during the payment process. It does not show the amount to pay

-It does not provide with user confirmation during the payment process

-Cannot login by pressing enter after entering the username and password

-No error prevention

-Gives errors with different browsers during login

-Services not clearly defined which might lead to error

Recognition rather than recall

-The user can be confused during navigation due to different menus provided in the website

-Navigation is hard during adding different services

-It is easy to navigate no need to remember

Flexibility and efficiency of use

-The website appearance changes in other browsers

-The website works well only with internet explorer and does not work well with other browsers

-The options under pop down menu in the home page of the website is hard to click sometimes

-Cannot pay multiple bills at a time

Aesthetic and minimalist design

-Irrelevant information is provided which is disturbing in the website

-User confirmation is lacking during the transaction process

-It provides with some irrelevant information which leads to confusion -The tab buttons not properly aligned in the website

-Irrelevant information diminishes the user action

Help users, diagnose, and recover from errors

-There is no help to recover from errors, the errors are not informative

-Few errors provide numbers and do not give information to avoid the error

-No recover of errors, error -It doesn’t mention that the website only works well with internet explorer -Provides error numbers which does not help recover errors by the user

- It doesn’t help in recovering errors -Gives error codes which are of no use to the user

-No proper password recover option

Help and documentation

-No help provided in the website, no descriptions of the services provided -The trouble shooting is poorly designed

-There is no help section provided in the website but provides a demo which has to be downloaded and played by the user which is a poor for m of help

-No help section provided in using the website

8 3.1 Analysis

Usability evaluation was performed by heuristic evaluation and interviews. All the major usability problems which are identified by heuristic evaluation have been confirmed by the users through interviews.

The usability problems identified by performing interviews depends on the interviewee, as interviewees 1,3,5 and 7 only found few usability problems. All the interviewees were regular users of internet except interviewee1. Interviewee 1 is not a regular user and uses internet for only payment of bills. Three interviewees were students and the rest were employees in different areas. There was no real difference between the problems identified by students and employees. The problems identified by interviews identified more problems than heuristic evaluation, in payment process of the website. The identification of usability problems was different with each interviewee, but all the interviewees faced similar problems in user control and help sections of the website.

The problems identified by heuristic evaluation are performed by 3 evaluators. All the three evaluators have identified usability problems in all the ten usability heuristics. These evaluators identified more usability problems than interviews, in Flexibility and efficiency of use, Help and documentation and Visibility of System status.

The total number of usability problems found by performing both the methods is 44 and out of them, major problems identified are 19 and minor problems identified are 25. The usability problems which are identified as major and minor are presented in Table 3. There were many similar problems identified in testing and inspection methods but few additional problems were also identified by both the methods.

There is no help section in the website, even though the usage of the website is not hard, it is necessary to provide a proper help section. The navigation of the website is also not convenient and there is no prevention of errors (for instance, the website does not provide the amount to pay which can lead to errors). The appearance of information in the website can be improved; these are few problems which are identified by both the methods. By using two usability evaluation methods, more number of usability problems was identified.

As shown in figure.2 more number of major problems are identified in User control and freedom, Consistency and Standards, and Flexibility and efficiency of use. These problems have been identified by using the responses from both the methods.

9 Table.3 Usability problems

Type of problem Description of the problem

No back option provided during navigation Pressing the home button logouts the user

No User confirmation procedures of the payment process

Sometimes technical errors occur during payment No proper recover of errors during transaction No emergency exit during navigation Cannot reset changes

Works well with only internet explorer Problem with choosing pop down menu

It doesn’t help to recover errors rather gives error number Major No proper information of the bill

No proper password recovery for this website Should check the bank statement every time

Can include more banks and increase number of services

Selection of area for payment is confusing and navigation is little hard

It does not provide information about the services

Does not prevent errors during payment process

The website appearance changes in other browsers

No help section provided

No hierarchical design of the information

Tab menus in homepage are confusing

Lack of user friendliness

Contains irrelevant information and is better to divide the payment process

Alignment of data can be improved

Font size can be increased

No automatic payment of bills for every month

Cannot pay multiple bills at a time

Navigation is difficult in some pages

Inconsistent wording in home page among tab menus

Language is more technical, difficult to understand

No error prevention during login

Minor Redundant information is provided in the home page which is confusing

No feedback within reasonable time during the web process

The website uses acronyms which might not be understandable for everyone

The structure and layout is not coherent

The system status is not mentioned during the navigation of the website

Cannot login by using keyboard after entering the username and password

Navigation is hard during adding different services

The tab menus not properly aligned in the website

The website doesn’t say that it only works well with internet explorer

A demo is provided in the website which is a poor form of help

Gives errors with different browsers during login

Information is not clear during registration and adding of services

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A graph has been illustrated to present the number of major and minor usability problems identified, for each usability heuristics in figure 2. It has number of problems as x-axis and usability heuristics as y-axis, where n is 44.

Figure 2: Graph presenting major and minor problems for each heuristic

Conclusion & Discussion

4 Conclusion

Main research question:

How is the usability of an online payment service in a public website?

The usability evaluation performed by heuristic evaluation and interviews had identified usability problems from both non-user and user point of view. Using both the methods, more number of usability problems were identified which are necessary for the improvement of online payment service in a public website.

How is the usability evaluation using an inspection method?

The evaluators had identified usability problems in all usability heuristics and the problems which are found more in heuristic evaluation than interviews were in Flexibility and efficiency of use, Help and documentation and Visibility of System status of the website.

0 1 2 3 4 5 6 7

Visibility of system status Match between system and …

User control and freedom Consistency and standards Error prevention Recognition rather than recall Flexibility and efficiency of use Aesthetic and minimalist design

Help users recognize, … Help and documentation

Number of usability problems

U sab il ity h e u r is ti c s

Major and Minor problems

Minor problems Major problems

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How is the usability evaluation using a testing method?

Interviews were performed which is a usability testing method, and the problems identified depends on the kind of interviewee but the occupation of the user did not play any role in identifying the usability problems. The problems which are found more in interviews than heuristic evaluation were in the payment process of the e-service.

How to identify different usability problems?

The major usability problems identified by heuristic evaluation were confirmed by the users who participated in interviews. There were a large number of similar problems identified by both the methods but few additional problems have been identified by both the methods. The use of both methods helps in identifying more usability problems than any single evaluation method.

4.1 Discussion

The problems identified from a usability evaluation can be used as a feedback for the designers of the website, so the usability problems identified have been divided into major and minor categories. The major problems are considered the first priority problems while the minor problems are the second priority problems; this makes it easy for the designers to identify different usability problems.

The evaluators in heuristic evaluation deliberately search for problems in the website’s usability while the users of the website who participated in the interviews do not intentionally search for problems; they only identify the problems faced during their usage of the website. The interviews give users perception of usability problems. This gives a two-dimensional way of finding usability problems. There were few problems found more in interviews than in heuristic evaluation and in the same way there were few problems identified more in heuristic evaluation than in interviews. Thus there were different usability problems found by each usability evaluation methods.

The usage of two or more usability evaluation methods was proposed for the usability evaluation of public websites and this case confirms that more information about usability problems can be achieved even by the use of two evaluation methods. This also shows that more number of usability problems can be identified using two usability evaluation methods than any single evaluation method. This kind of usability evaluation has been carried out before for transactional web applications, but it was applied to a public website in this paper. The heuristic evaluation should be used as the usability inspection method as it is an efficient one in identifying the usability problems but different methods can be used from the usability testing methods other than the interviews. Further research can be performed on various other public websites using two or more usability evaluation methods.

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References

Literature

Prabhu, C. (2004). E-GOVERNANCE: Concepts and Case Studies. New Delhi: Prentice Hall of India. Oates, B. J. (2006). Researching Information Systems and Computing. London: Sage.

Sharp, H., Rogers, Y., & Preece, J. (2007). Interaction design: Beyond human computer interaction. John Wiley & Sons Ltd.

Articles

Layne, K., & Lee, J. (2001). Developing fully functional E-government: A four stage model. Government Information Quarterly , 122-136.

Lili, W., Stuart, B., & Jon, G. (2005). Evaluating Web-based e-government services with a citizen-centric approach. Hawaii International Conference on System Sciences (pp. 1-10). IEEE.

Liu, F. (2008). Usability Evaluation on Websites. IEEE , 141-144.

Nielsen, C. M., Overgaard, M., Pedersen, M. B., & Stage, J. (2005). Feedback from Usability Evaluation to User Interface Design: Are Usability Reports Any Good? In Human-Computer Interaction - INTERACT (pp. 391-404). Springer Berlin.

Nielsen, J. (1992). Finding Usability Problems Through Heuristic Evaluation. ACM , 373-380. Otaiza, R., Rusu, C., & Silvana, R. (2010). Evaluating the Usability of Transactional Web Sites. Advances in Computer-Human Interactions (pp. 32 - 37). IEEE Xplore.

Wood, F. B., Siegel, E. R., Lacroix, E.-M., Lyon, B. J., Benson, D. A., Cid, V., et al. (2003). A Practical Approach to E-Government Web Evaluation. IEEE , 22-28.

Websites

esevaonline. (2001). Retrieved 04 02, 2010, from eseva: www.esevaonline.com

EU. (2004). ICT for Government and Public Services. Retrieved 04 15, 2010, from Europe's Information Society: http://ec.europa.eu/information_society/activities/egovernment/index_en.htm Nielsen, J. (2005). Heuristic Evaluation. Retrieved 04 08, 2010, from

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Appendix-A

[A] What is your occupation and how often do you use Internet?

[B] Does the website keep you informed about your position in the web process?

[C] Is the language in the website easy to understand?

[D] Does the website provide you to undo and redo your changes?

[E] Does the website provide you with clear information?

[F] Does the website help you in recognizing your data and reduce errors?

[G] Is the website easy to use and does it reduce your memory load

[H] Is the website adaptable and efficient to use?

[I] Does the website provide you with irrelevant information during your process?

[J] Does it help you recover from errors?

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Appendix-B

These are the general principles for user interface design and were developed by (Nielsen J. , Heuristic Evaluation, 2005)

S.No Usability Heuristics Description

1 Visibility of system status The system should always keep users informed about what is going on, through appropriate feedback within reasonable time

2 Match between system and the real world

The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order

3 User control and freedom

Users often choose system functions by mistake and will need a clearly marked "emergency exit" to leave the unwanted state without having to go through an extended dialogue. Support undo and redo.

4 Consistency and standards

Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions

5 Error prevention

Even better than good error messages is a careful design which prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action.

6 Recognition rather than recall

Minimize the user's memory load by making objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate

7 Flexibility and efficiency of use

Accelerators -- unseen by the novice user -- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.

8 Aesthetic and minimalist design

Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.

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Help users recognize, diagnose, and recover from

errors

Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.

10 Help and documentation

Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to Search, focused on the user's task, list concrete steps to be carried out, and not be too large.