1 Pertemuan 12 Interface Matakuliah: M0446/Analisa dan Perancangan Sistem Informasi Tahun: 2005 Versi: 0/0

2 Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : Menunjukkan Interface

3 Outline Materi User dan Sistem Interface Pola User Interface Menentukan pola user interface

4 Aktivitas utama dalam Analisis Application Domain

5 Terminologi Interface: Fasilitas yang membuat model sistem dan function dapat berinteraksi dengan actors. User interface: Interface untuk users. System interface: interface ke sistem lain. Usage context: The application domain characterized by actors and use cases.

6 User Interface Are very important: they can make or break system use and benefit realisation. Needs to carefully fit the usage context. Need to be designed carefully - small details multiply difficulties with usage. Need to account for the different kinds of users with different skills and capabilities. Very difficult to design without feedback - generally must be tested with users.

7 Systems Interface(s) May need interfaces for non-human actors, i.e. other systems Not commonly used for administrative systems More common for monitoring & control systems –direct sensors in the environment - e.g. temperature –direct intervention, e.g. motors, switches –may also input or output from other computer systems Need to design and make sure that these technical connections can be realized

8 Sub-activities in Interface Analysis

9 Tailor Usability to Context Usage is relative to usage context

10 Study the Usage Context Study both human actors and use cases –Does the individual user solve several tasks in parallel? –Does the user move physically while working? –Is the work often interrupted? –Are certain use cases significantly different from the typical use cases? –Do certain work tasks require a quick response from the computerized system? –How is it ensured that the users notice when the computerized system performs a signal function?

11 Explore User-Interface Patterns A user interface usually mixes several patterns or styles Four main patterns/styles –menu –form filling –command language –direct manipulation (also natural language)

12 Menu Selection Advantages –Shortens learning –Reduces key-strokes –Structures decision making –Allows easy support of error handling –High level tools allow for easy programming Disadvantages –Risk of too many menus –Slows the frequent user down –Consumes screen space –Requires rapid display rate

13 Form Filling Advantages –Simplified data entry –Requires modest training –Makes assistance convenient –High level tools allow for easy programming Disadvantages –Consumes screen space

14 Command Language Advantages Flexible –Appeals to “power” users –Supports user initiative –Convenient for creating user-defined macros Disadvantages –Poor error handling –Requires extensive training

15 Direct Manipulation Advantages –Immediately visible result of interaction –Useful for both casual and frequent users –Can be extremely efficient Disadvantages –Effort required to develop –Difficult to invent meaningful icons, symbols, etc., unless can rely on standard objects

16 Dialog Style: Function-Oriented vs Object-Oriented Is the interface primarily based on functions or objects? Need both, but which choose first? –I.e., does the user choose the function first, then choose the object or vice versa? Function-oriented dialogues are better for routine, automated work Object-oriented ones are better for varied individual work tasks as they give more flexibility –But, usually require more development time and effort

17 Some Guidelines A dialogue needs to be simple, natural, and consistent. Requirements placed on the users’ memory need to be minimal. Feedback must be informative and constructive. Errors must be prevented. Detailed discussion is beyond the scope of this unit.

18 Determine User-Interface Elements Representations of objects in the model –Many possibilities: icons, fields, tables, diagrams, windows –Need a clear & consistent system of representations Activation of functions –Buttons, menu screens, pull-down/pop-up menus –Also need support for visualisation and feedback –Needs to be consistent and fit within the dialog pattern/style Result is a list of user-interface elements

19 Describe Interface Elements User Interface: –General effect: colours, fonts, types of menus, types of icons, default positions –Navigation: dialog linkages between buttons, menus, screens, windows, etc. –Computer screens/windows/forms, etc.: layout, interactivity, consistency –Outcome of activity is screen/form designs, navigation diagram and other descriptions

20 Evaluate the User Interface A User Interface cannot be constructed bottom up without experiments using prototypes. Should be a carefully controlled process using the five sub-activities. Planning needs to lead to concrete evaluation and quick development with efficient tools. Preparation needs to determine how collaborate with users, ensure realism, and select good example tasks that enhance feedback.

21 Explore Systems Interface Patterns Consider what/how data should be sent to and received from other systems (if any) Other systems may be –simple external devices: sensor, switch, or motor use simple read or activate device patterns –complex computer systems: need a communication protocol which may be supplied or need to be designed

22 Read External Device Pattern Read either regularly or dependent on an event Memory object can just be the model object

23 Interaction Protocol A protocol defines command facilities supporting the possible use cases for a system by another Is agreed upon by designers of the two systems (unless one has already been designed/built!) Specify a pattern for interaction using a list of commands for each side and their expected responses –Separate protocol item named for each command –E.g. Request some info or Prepare to accept info –Commands may check the state of the other system

24 Determine and Describe the Systems Interface Elements What other computer systems will the system be connected to and exchange information with? –What protocol(s) will be needed? Will the system be connected directly to the problem domain through external devices? –What external device read or write interfaces are needed? Result is a list and specification of each.

25 Evaluate System Interfaces Protocols can be tested on pencil and paper by working through use cases Ultimate test is that the physical connections actually work –If there is any doubt, these connections need to be tested as early as possible –Build and test technical feasibility prototypes

26 Principles of Interface Analysis Tailor usability to the application domain –need to know who the users are and in what situations the computerized system will be used Experiment and iterate –interfaces are complex and interact with users in ways that can’t be anticipated –experiments need to be planned, efficient, and realistic - and likely will be repeated

27 Principles of Interface Analysis (2) Identify all interface elements –Important not to leave anything out! –Details can be supplied/determined later, as long as the basic structure is clear and coherent