human computer interaction chapter 4 implementation support and evaluation techniques - dr. j....

Chapter 4

Chapter 4Implementation Support and Evaluation Techniques

1Human Computer Interaction

26 May 2016Presented by Dr. J. VijiPriya, Assistant Professor, Hawassa University, Ethiopia

26 May 2016Presented by Dr. J. VijiPriya, Assistant Professor, Hawassa University, Ethiopia2Implementation SupportElements of windowing systems Programming the applicationUser interface management systemsEvaluation TechniquesWhat is evaluation?Goals of evaluationChoosing an evaluation method

Implementation Support3

The detailed design specification gives the programmer instructions ( what the interactive application must do)The programmer must translate that into machine executable instructions ( how that will be achieved on the available hardware devices). (Ie. the level of the software that runs the hardware devices )

This software provides the ability to do things like read events from various input devices and write primitive graphics commands to a display.

The job is very tedious and highly error prone .


Windowing Systems4 are core support for separate and simultaneous user system activityElements of Windowing Systemssome visual display screen, a keyboard and some pointing device, such as a mouseA given windowing system will have a fixed generic language for the abstract terminal (called its imaging model) to describe very arbitrary images and then can be translated to the language of many other specific devices (ie device driver) and then any application program can access it.Example for image models for output and (partially) inputpixels:-rows and columns of points on or off , color

Graphical Kernel System (GKS):- Collection of segment model the screen ,each segment indicates commands

Programmers' Hierarchical Interface to Graphics (PHIGS):- collection of editable segments model the screen.

PostScript:-language was developed by Adobe Corporation which models the screen as a collection of paths which serve as infinitely thin boundaries or stencils which can be filled in with various colors or textured patterns and images.


Windowing systems Con

5The other feature of windowing systems is resource sharing: achieving simultaneous user tasks. supports independent processes isolation of individual applicationsThe role of a windowing systemmanagement of multiple, independent but simultaneously active applications.independence from the specifics of programming separate hardware devices;


The role of a windowing system6


Programming the Application

7Two programming paradigms- used to organize the flow of control within the application. readevaluation loopnotification basedThe windowing system does not necessarily determine which of these two paradigms is to be followed.Read-Evaluation loopProgramming on the Macintosh follows this paradigm. The server sends user inputs as structured events to the client application. The client application is programmed to read any event passed to it and determine all of the application-specific behavior that results as a response to it. 26 May 2016Presented by Dr. J. VijiPriya, Assistant Professor, Hawassa University, Ethiopia

Programming the Application con

8Read-Evaluation loop Programming Paradigm: Logical flow and pseudo-code for Client application

repeatread-event(myevent)case myevent.typetype_1:do type_1 processingtype_2:do type_2 processing...type_n:do type_n processingend caseend repeat26 May 2016Presented by Dr. J. VijiPriya, Assistant Professor, Hawassa University, Ethiopia


9Notification based programming paradigm

In which the main control loop for the event processing does not reside within the application.

The application program informs the notifier what events are of interest to it, and for each event declares one of its own procedures as a callback before turning control over to the notifier. When the notifier receives an event from the window system, it sees if that event was identified by the application program and, if so, passes the event and control over to the callback procedure that was registered for the event. After processing, the callback procedure returns control to the notifier, either telling it to continue receiving events or requesting termination26 May 2016Presented by Dr. J. VijiPriya, Assistant Professor, Hawassa University, Ethiopia


10

Notification based programming paradigm


User Interface Management Systems11The term UIMS is used quite widely in both industrial and academic circles and has come to represent a variety of topics.

The main concerns of a UIMS, for our purposes, are:a conceptual architecture for the structure of an interactive system which concentrates on a separation between application semantics and presentationsupport techniques for implementing a separated application and presentation whilst preserving the intended connection between themsupport techniques for managing, implementing and evaluating a run-time interactive environment.

There are many good arguments to support this separation of concerns:Portability to allow the same application to be used on different systems.Reusability -components can be reused in order to cut development costs.Multiple interfaces To enhance the interactive flexibility of an application, several different interfaces can be developed.Customization The user interface can be customized by both the designer and the user to increase its effectiveness without having to alter the underlying application


User Interface Management Systems Con12The logical components of a UIMS Presentation The component responsible for the appearance of the interface, including what output and input is available to the user.Dialog control The component which regulates the communication between the presentation and the application.Application interface The view of the application semantics that is provided as the interface.


Evaluation Techniques13What is Evaluation?tests usability and functionality of systemoccurs in laboratory, field and/or in collaboration with usersevaluates both design and implementationshould be considered at all stages in the design life cycleGoals of Evaluationto assess the extent and accessibility of the systems functionality, to assess users experience of the interaction,to identify any specific problems with the system26 May 2016Presented by Dr. J. VijiPriya, Assistant Professor, Hawassa University, Ethiopia

Evaluation Techniques con14Choosing an Evaluation Methodhow do we decide which methods are most appropriate for our needs?Each method has its particular strengths and weaknesses and each is useful ifapplied appropriately. However, there are a number of factors that should be taken into account when selecting evaluation techniques.

The choice of evaluation method is largely dependent on what is required of the evaluation

when in process:design vs. implementationstyle of evaluation:laboratory vs. fieldhow objective:subjective vs. objectivetype of measures:qualitative vs. quantitativelevel of information:high level vs. low levellevel of interference:obtrusive vs. unobtrusiveresources available:time, subjects, equipment, expertise


Evaluation Techniques con15Evaluation methods vary in the stage at which they are commonly used and where they can be used. Some are more subjective than others and provide qualitative rather than quantitative measures. Some provide immediate information while others get feedback after the event. However, the more immediate methods also tend to intrude (interrupt) most seriously on the interaction. Finally, some require more resources in terms of time, equipment and expertise than others.


human computer interaction chapter 4 implementation support and evaluation techniques - dr. j....

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