What do you mean by directing manipulation and indirect manipulation

Q.What do you mean by directing manipulation and indirect manipulation? (5 M) (DEC 16 /MAY 16 /DEC 17)

Ans:-

Direct manipulation:-

• Definition:- Direct manipulation (DM) is an interaction style in which users act on displayed objects of interest using physical, incremental, reversible actions whose effects are immediately visible on the screen.
•  Example:
• dragging a document to the trash
• changing the size of a triangle by interacting with a visual representation of a triangle
• inserting characters in a document by pointing to where they should go (with a mouse/cursor/insertion point) and then typing
• “dialing” a phone number by pushing numbers on a keypad
• playing a song using controls like a physical tape deck or CD/DVD player

Moving a file on MacOS using direct manipulation involves dragging that file from the source folder and moving it into the destination folder.

• Characteristics:
• The task objects are manipulated by physical actions, such as clicking or dragging, rather than by entering complex syntax.
• There is a visible and continuous representation of the task objects and their actions. Consequently, there is little syntax to remember.
• Rapid learning
• Their effects on task objects are immediately visible.
• Reversibility of (almost) all actions 
• Users can explore without severe consequences 
• Syntactic correctness 
• every operation is legal
• Disadvantages:
• DM is slow
• Repetitive tasks are not well supported.
• Some gestures can be more error-prone than typing
• Accessibility may suffer

Indirect manipulation:-

• Indirect manipulation substitutes words and text, such as pull-down or pop-up menus, for symbols, and substitutes typing for pointing.
• Most windows system are a combination of both direct and indirect manipulation 
• Example:
• A menu ma be accessed by pointing at a menu icon and then selecting it( direct manipulation)
• The menu itself, however, is a textual list of operations (Indirect manipulation)
• When an operation is selected from the list, by pointing or typing the system executes it as a command

• Disadvantages:
• The operation may be difficult to conceptualize
• Graphics capability limited
• Amount of space available for placing manipulation controls in the window border may be limited.
• Difficult to remember all the necessary operations

What are the Advantages and Disadvantages of Digital or Graphical systems

Q. What are various advantages of Digital and Graphics System? (DEC 17) 5M

Q. What are the Advantages and Disadvantages of Digital or Graphical systems? Explain in brief. (DEC 16) 10M

Digital System

Advantage

1. Have made possible many scientific, industrial, and commercial advances that would have been unattainable otherwise.
2. Less expensive
3. More reliable
4. Easy to manipulate
5. Flexibility and Compatibility
6. Information storage can be easier in digital computer systems than in analog ones. New features can often be added to a digital system more easily too.

Disadvantage

1. Use more energy than analog circuits to accomplish the same tasks, thus producing more heat as well.
2. Digital circuits are often fragile, in that if a single piece of digital data is lost or misinterpreted the meaning of large blocks of related data can completely change.
3. Digital computer manipulates discrete elements of information by means of a binary code.
4. Quantization error during analog signal sampling.

Graphical System

Advantage

1. Symbol recognized faster than text: Researchers have found that symbols can be recognized faster and more accurately than text and that the graphical attributes of icons such as shape and color are very useful for quickly classifying object, elements or text by some common property. These icons allow speedy recognition of the type of message being presented.
2. Faster learning: It has been found that a graphical, pictorial representation aids learning and symbols can also be easily learned.
3. Faster use and problem solving: Visual or spatial representation of information has been found to be easier to retain and manipulate and leads to faster and more successful problem solving. Symbols have also been found to be effective in conveying simple instruction.
4. Easier remembering: Because of greater simplicity, it is easier for casual user to retain operational concepts.
5. More natural: Graphical representations of objects are thought to be more natural and closer to innate human capabilities. It has also been suggested that human mind has a powerful image memory.
6. Foster more concrete thinking: Displayed objects are directly in the high-level task domain or directly usable in their presented form. There is no need mentally to decompose tasks into multiple commands with complex syntactic form. The need for abstract thinking is therefore minimized.
7. Fewer errors: More concrete thinking affords fewer opportunities for errors. Error messages are less frequently needed.
8. Increased feeling of control: The user initiates actions and feels in control. This increases user confidence and hastens system mastery.
9. Less anxiety concerning use: Hesitant or new users feel less anxiety when using the system.
10. More attractive: Direct-manipulation system is more entertaining, cleverer and more appealing.
11. May consume less space: Icons may take up less space than the equivalent in words.
12. Replaces national languages: Language-based systems are seldom universally applicable. Icon possesses much more universally than text and much more easily comprehended worldwide.
13. Easily augmented with text displays: Where graphical design limitations exist, direct- manipulation system can easily be augmented with text displays.
14. Low typing requirements: Pointing and selection controls such as the mouse or trackball eliminate the need for typing skills.
15. Smooth transition from command language system: Moving form a command language to a direct-manipulation system has been found to be easy.

Disadvantage

1. Greater design complexity: Controls and basics alternatives must be chosen from a pile of choices numbering in excess of 50. The design potential may not necessarily result in better design, unless the choices are thoughtfully selected and consistently and simply applied. With graphics, the skill of the designer is increasingly challenged.
2. Learning still necessary: The meaning of many words and icons may not be known. A severe learning and remembering requirement is imposed on many users, and it takes a while to get up to speed. System providers estimate that becoming accustomed to a graphical interface should require about eight hours of training. Other experts say the learning time is closer to 20 or 30 hours.
3. Lack of experimentally-derived design guidelines: The graphical interface is still burdened today by a lack of widely available experimentally-derived design guidelines. Too many variables that must be controlled make meaningful cause and effect relationships very difficult to uncover.
4. Inconsistencies in technology and terminology: The inconsistencies occur because of copyright and legal implication, product differentiation consideration, and our expanding knowledge about the interface.
5. Working domain is the present: While direct-manipulation system provides context, they also require the user to work in the present.

Explain what do you mean by keyboard Accelerators

Q. What do you mean by keyboard accelerators? Explain (DEC 16 / MAY 16/ MAY 19) 5M

Q,Explain what do you mean by keyboard Accelerators? (DEC 17 / MAY 18) 10M

1.      Menus often offer keyboard accelerators, key combinations that have the same effect as selecting the menu item.

2.      This allows more expert users, familiar with the system, to manipulate things with-out moving off the keyboard, which is often faster.

3.      The accelerators are often displayed alongside the menu items so that frequent use makes them familiar.

4.      Unfortunately most systems do not allow you to use the accelerators while the menu is displayed. So, for example. the menu might say

Find        F3                  

5.      However when the user presses function key F3 nothing happens. F3 only works when the menu is not displayed- when the menu is there you must press ‘F’ instead.

Discuss issues related to Long Term Memory and short Term Memory.

Q. Discuss issues related to Long Term Memory and short Term Memory. (DEC 16 / MAY 16) 5M

Issues related to Short-term memory

Short-term memory, typically, requires concentrated effort on the part of the individual concerned. If they become distracted by environmental factors then that concentration can be broken and the content of short-term memory may be lost. For instance, even a momentary distraction can cause a user to forget the name of a file or of a password that they havent used before.

Issues related to Long-term memory

Long-term memory, typically, it is less easy to remember information that has passed from short-term to long-term memory. In consequence, a greater source of distraction or disruption would be required to impair their memory. A, typically, example is that even expert computer users may make mistakes if they attempt to perform two familiar tasks in parallel. Both may draw upon long-term memory but there can be interference effects.

What is direct and indirect manipulation ?

Q. What is direct and indirect manipulation? (DEC 16 / MAY 16 / DEC 17 ) 5M
Q. Differentiate between direct and indirect manipulation. (MAY 19) 5M

Direct Manipulation

The term direct manipulation is given by Shneiderman (1982) as they possess the following characteristics:

i. The system is portrayed as an extension of the real world.

ii. Continuous visibility of objects and actions.

iii. Actions are rapid and incremental with visible display of results.

iv. Incremental actions are easily reversible.

Example for direct manipulation:

Driving an automobile

The scene is directly visible through the front window and performance of actions such as braking or steering has become common knowledge in our culture. To turn left, the driver simply rotates the steering wheel to the left. The response is immediate and the scene changes, providing feedback to refine the turn.

In the above example, a driver looking at an object directly manipulates the scenario by his sudden action, which can be referred as direct manipulation.

Indirect Manipulation

In practice, direct manipulation of all screen objects and actions may not be feasible because of the following:

i. The operation may be difficult to conceptualize in graphical system.

ii. The graphics capability of the system may be limited.

iii. The amount of space available for placing manipulation controls in the window border may be limited.

iv. It may be difficult for people to learn and remember all the necessary operations and actions.

When this occurs, indirect manipulation is provided. Indirect manipulation substitutes words and text, such as pull-down or pop-up menus, for symbols and substitutes typing for pointing.

Most window systems are a combination of both direct manipulation and indirect manipulation. A menu may be accessed by pointing at a menu icon and then selecting it (direct manipulation) or the menu itself is a textual list of operations (indirect manipulation).

Andrew File System(AFS)

Q. Short Note on Andrew File System(AFS) (December 16) (10 Marks)

Ans -

1. Distributed network file system which uses a set of trusted servers to present a homogeneous, location transparent file name space to all the client workstation
2. Distributed computing environment developed at Carnegie Mellon University (CMU) for use as a campus computing and information system [Morris et al. 1986].
3. Intention is to support information sharing on a large scale by minimizing client-server communication
4. Achieved by transferring whole files between server and client computers and caching them at clients until the servers receives a more up-to-date version.

Features of AFS

• Uniform namespace
• Location-independent file sharing
• Client-side caching
• Secure authentication
• Replication
• Whole-file serving
• Whole-file caching

Working

Implemented as 2 software components that exists as UNIX processes called Vice and Venus

Vice: Name given to the server software that runs as a user level UNIX process in each server computer.

Venus: User level process that runs in each client computer and corresponds to the client module in our abstract model. Files available to user are either local or shared

Local files are stored on a workstation's disk and are available only to local user processes.

Shared files are stored on servers, copies of them are cached on the local disk of work stations.

Explain Goal Directed Design in detail

Q. Explain Goal Directed design process in brief. (5 M)(DEC 16/ MAY 19)

Q. Explain Goal Directed Design in detail.(5 M)(DEC 17)

Q. Write Short Note on: Goal Directed Design (5 M) (MAY 17/DEC 18/MAY 19)

Ans:-

Goal Directed Design Process(GDD):

• Goal Directed Design is a user-centered methodology developed by Alan Cooper to address situations.
• Goal directed design identifies the goals and behavior of a user.
• In GDD basically two important factors i]User ii] Stockholders
• GDD is combinations of following:

• Stockholders interview
• Market research
• Detailed users model
• user interview and persona
• scenario based design

• Goal Directed Design describes a six-step process as follows:
1. Research 
2. Modeling
3. Requirement definition
4. Framework definition
5. Refinement phase
6. Support

Fig: Goal Directed Design Process

1.Research:

• This is initial phase to bridge the gap between the users and developer
• The research generates information about potential or actual users.
• Research help to identify behavior patterns and personas in the modeling phase

2.Modeling:

• The outcome of research phase is synthesized into domain and user models.
• Domain models includes information flow and work flow
• Here we can identify the detailed persona, composite user arch types that represent distinct behavior,attitude and goals identified in research phase

3. Requirement definition:

• This phase provides the much needed connectivity between the user and other models and design framework
• This phase involves an analysis of persona data and functional needs (expressed in term of objects, actions, and contexts), prioritized and informed by persona goals, behaviors, and interactions with other personas in various contexts.
• These are the requirements for each persona: the data they need to see and the functional needs they have for working with this data

4.Framework definition:

• The framework is like sketching the layout for the house before detailed blueprints is created
• In this phase a basic framework for the system behavior, visual design as well as physical form of design is proposed
• In this phase interaction team may specify the interaction framework

5.Refinement phase:

• In this phase enhances focus on design details and implementation 
• It also helps in developing the storyboard in high detail 
• Shortcoming in previous phase are altered or updated to provide user with goal oriented design
• This phase is similarly to the Framework Definition phase, but with greater focus on task coherence, using key path and validation scenarios focused on story-boarding paths through the interface in high detail

6.Support phase:

• This phase fulfill the futuristic requirements of the user. Even after user level acceptance,it is always recommended to carry out continuous refinement and additional development if required 

What do you mean by device based and screen based control, Explain

Q. Write short note on: Device Based Control (5 M)(MAY 18/MAY 19)

Q. Write short note on: Screen Based Control (5 M) (MAY 18)

Q. What do you mean by device based and screen based control, Explain? (10 M)(DEC 16)

Q. Provide different device based and screen based control for following.   (10 M) (MAY 17)

           (i) Filling up Online Application for Admission to Engineering Course.

          (ii) Online payment of Utility Bills such as Telephone, Electricity and Water charges etc.              

Ans:-

1.Device Based Control:

• Are nothing but input devices,are the mechanisms through which people communicate their desires to the system.
• There are two types of Devices:- 
•  Direct Devices :-operated on the screen itself. e.g. the light pen, the finger, and voice
• Indirect Devices :-operated in a location other than the screen, most often on the desktop
• Some Characteristics of  Device-Based Controls:
• point at an object on the screen.
• For select the object or identify it as the focus of attention.
• Drag an object across the screen.
• Draw something free form on the screen.
• To track or follow a moving object.
• To orient or position an object.
• To enter or manipulate data or information.
• Trackball:-
• A spherical object (ball) that rotates freely in all directions in its socket.
• Direction and speed is tracked and translated into cursor movement.
• Advantages:-
• Direct relationship between hand and pointer movement in terms of direction and speed.
• Does not obscure vision of screen.
• Does not require additional desk space (if mounted on keyboard).
• Disadvantages:-
• No direct relationship exists between hand and pointer movement in terms of distance.
• Requires a degree of eye-hand coordination.
• Requires hand to be removed from keyboard keys.
• Requires different hand movements.
• Graphic Tablet:-
• Pressure-, heat-, light-, or light-blockage-sensitive horizontal surfaces that lie on the desktop or keyboard.
• May be operated with fingers, light pen, or objects like a stylus or pencil.
• Pointer imitates movements on tablet.
• Advantages:-
• Direct relationship between touch movements and pointer movements in terms of direction, distance, and speed.
• More comfortable horizontal operating plane.
• Does not obscure vision of screen.
• Disadvantages:-
• Movement is indirect, in a plane different from screen.
• Requires hand to be removed from keyboard.
• Requires hand to be removed from keyboard keys.
• Requires different hand movements to use.
• Requires additional desk space.

2.Screen Based Control:

• sometimes called widgets,are the elements of a screen that constitute its body.
• These are the graphic components which we can see on the screen and can interact with them.
• Screen based controls do can:
• selection of a particular value.
• Editing of a particular value.
• Display a particular piece of text, value,or graphic.
• Cause an action to be performed.
• Types:
• Buttons
• A square or rectangular-shaped control with a label inside that indicates action to be accomplished
• Label may consist of text,graphics or both
• Purpose:- i] To start actions    ii] To change properties

• Text entry/read-only controls
• Control is usually rectangular in shape,in which text may be entered or may be displayed for read-only purposes.

• Selection controls
• To select a particular values
• Type:i]Radio buttons    ii]Check boxes

• Combinations entry/selection controls
• A control can have characteristics of both a text field and a selection field
• Here information is either typed or selected and placed in it.
• Types:- 

                                           i]Spin boxes       

                                          ii]Attached combination boxes 

                                         iii]Drop-down/pop-up combination boxes

• Others operable controls:
• Slider
• A scale exhibiting a range of values.
• Used in smart phones for setting brightness,volume.In PC for setting screen size, resolution etc.
• Best example: MX player,VLC player
• Date picker
• A drop-down list box that display a 1-month calendar in the drop-down list box.so that month can be changed by pressing command buttons with left-and right pointing arrows
• Tree
• A special list box control that displays a set of objects as hierarchical view
• Scroll Bar
• A vertical or horizontal bar commonly located on the far right or bottom of window with the help of which we can move the viewing area up,down,left,right.

Explain seven stages of actions and three levels of processing

Q.What are the three levels of processing? Explain.(5 M)(DEC 16/MAY 16/MAY 18)

Q.What are three levels of processing and seven stages of Action? How they are interrelated to each other?(10 M) (MAY 17)

Q.Explain seven stages of actions and three levels of processing.(10 M) (DEC 18/MAY 19)

Ans:-Three levels of processing as follows:

i    Visceral

ii   Behavioral 

iii  Reflective

Fig: Three levels of processing 

i. Visceral Level:

•  The most immediate level of processing.
•  Here the human reacts to audio, visual and other aspects of a product before experience it
•  It is the most primitive type of mental processing
•  Quick analysis and response to situations to determine whether there is a threat or an opportunity
• The look and feel of the product dominates the user in this level
• Our brain is trained to like and dislike based on our cultural belief and social upbringing
• Sends appropriate signals to the muscles (the motor system) and alerts the rest of the brain
• This is the start of effective processing
• E.g. Kids like Red or dark colors

 ii. Behavioral Level:

• Behavioral level is the site of most human behavior
• The emotional brain takes control of the decision making
• Allows us to analyze a situation, alter behavior
• Semantics and usability practices are addressed in this level.
• The behavioral level is the site of most human behavior
• The behavioral level is common to mammals and both the visceral and behavioral level can receive direct sensory input

iii. Reflective:

• Reflective level is the highest level of processing 
• All experience and its meaning is stored in human brain
• This level does not have direct access to either sensory input or the control of behavior
• This level does not have direct access to either sensory input or the control of behavior 
•  Watch over sensory input and tries to bias the behavioral level.

Seven stages of actions: The action cycle can be divided into two parts:
          i.Execution
          ii.Evaluation

• Seven stages are as follows:

1. Forming the goal
2. Forming the intention
3. Specifying an action
4. Executing the action
5. Perceiving the state of the world
6. Interpreting the state of the world
7. Evaluating the outcome

Fig: Seven stages of action

Execution part

      1.Forming the goal:

•  This is what you want.
•  It implies a goal-oriented design, which is very different from the task-oriented approach
•  Specifying/forming a goal about something that you want to accomplish

      2.Forming the intention:

• This is what would satisfy the goal
• Forming an intention to act

      3.Specifying an action:

• Selecting an action or a sequence of actions that will lead you to your set goal
• What do I have to do to achieve the intention?

     4.Executing the action:

• Execution of the actions
• Do the steps of the action to achieve the goal

Evaluation part

       5.Perceiving the state of the world:

• Using the senses to gather information
• Perceiving the state of system resulting from the action

     6.Interpreting the state of the world:

• Interpretation of this perception based on your expectations
• What has changed?

      7.Evaluating the outcome:

•  Is the evaluation successful the problem is solved , goal reached and so on
•  Did I achieve my goal?

Example:

1) My goal is going to a cafe across the street

2) I form the intention of crossing the street to reach the cafe

3) I select the action to press the button of the crosswalk signal for crossing the street

4a) I actually do press the button of the crosswalk signal (physical action)

4b) I do cross the street (physical action)

5) I perceive that I’m now across the street

6 ) I interpret this perception and..

7) …evaluate the outcome – was this action successful in moving closer to my goal? (Y/N)

What do you mean by persona? Mention steps in constructing persona

Q.What do you mean by persona? Mention steps in constructing persona (MAY 16 / MAY 17)   10M

Q.Mention steps in constructing persona (DEC16 /DEC17 /MAY18 ) 5M
Ans -

1. A persona is a prototypical user:
   -An imaginary, but very specific, example of a particular type of user.
   -Not “real”, but hypothetical.
2. A persona is used to role-play through an interface design and check if the design would meet the needs of such a user.
3. Steps in constructing persona:
   i. Personas can be adopted by various techniques.
   ii. Steps :
   a. Identify user behavioral patterns.
   b. Arrange interview as per user behavior.
   c. Recognize user behavioral patterns.
   d. Generate various user characteristics and relevant goals.
   e. Check for completeness of goals.
   f. Explain all attributes and behavior of user.
   g. Design various persona.

Goal directed design process in Human Machine Interaction

Q.Explain Goal Directed design process in brief. (DEC 16 / MAY 19) 5M

Q.Explain Goal Directed Design in detail. (DEC 17) 5M

Q.Write Short Note on: Goal Directed Design (MAY 17 / DEC 18 / MAY 19) 5M

Ans - The whole process of Goal directed design is broken down into six steps.

 

1. Research: 

In this stage you collect qualitative data about the users or potential users through field studies and interviews. You carry out a competitor analysis and interview key stakeholders to gather their requirements. When you’re finished you should be left with a set of instructions which describe how the product could be used.

2. Modelling:

The modelling stage can be broken down into two parts. In part one you define the domain model by building on the workflow patterns from the research stage. In part two you define the user model through the use of personas or key archetypes which represent identifiable groups of users.

3. Requirements Definition:

Stage three is critical for providing that link between the user model and other models. In this stage you focus on context scenarios to help define ‘a day in the life’ of a persona. You also consider business goals, technical considerations and brand guidelines during this stage but it’s the context scenarios which really make a big impact to the way you think and help generate a ton of ideas you might not have considered before.

4. Framework Definition:

During the framework definition stage you create the overall product concept and define the behavior and visual design of the product. You can also create prototypes during this stage.

5. Refinement:

In the refinement stage you place more focus on detail and refinement and at the end of this stage it’s recommended that you create your design documentation.

6. Development Support:

No matter how clear the vision is for the product things can and do change during development, budgetary and timeline concerns can affect which features get taken away or which new ones get added and it’s critical that the designer is on hand to offer advice and to make sure the overall design quality doesn’t get compromised.

Three levels of processing

Q.What are the Three levels of processing? Explain (DEC16/ MAY 16/ MAY 18) 5M

Q.What are three levels of processing and seven stages of Action? How they are interrelated to each other? (MAY 17) 10M

Q.Explain seven stages of actions and three levels of processing. (DEC 18 / MAY 19) 10M

Ans-   

Introduction

• The processing can be done in three steps, design is nothing but the effort to develop best user interface to communicate with machines.
• End user can share experiences by designing models and convert them into prototype for development.
• Three levels at which we process information available, the seven stages of our actions can be understood in simple way.
• Every stage will perform action on a particular level.
• Norman has given overview of such mapping.

 Level 1 :- Visceral level

• This is initial level of processing available information.
• In this step of processing human reacts to audio visual actions and other aspects of a product.
• The external look and touch feel of the product will dominate the user at this visceral level.
• A human need to decide things are good, bad, safe or dangerous.
• Human brains is trained to like or dislike things based on their own thinking level.
• E.g.
  
  • Boys like blue
  • Girls like pink
  • Kids like Red or dark colors
  • Indians like spicy food, etc.
• Visceral design often refers to creating best user interface and graphical appearance.
• The developer can have creative skills of a visual and graphical designs, it creates lot of impact to users.
• Once this level is approved, we proceed towards actual work.
• If this level is not designed properly, other levels will need more effort for product acceptance.
• The user of a product is one of the most critical to decide about product.

Level 2 : - Behavioral Level

• The emotional brain is important while making decision.
• The more detailed level of product description than visceral.
• It is very difficult to work with complex systems, than working on simple environments.
• Semantics and usability practices are addressed in this level.
• It decides the behavior and feedback given by the product.
• For example , a dialog box with an error message inform user about next step of action.
• ON and OFF mark on an electrical switch can simply explain its operation.

Level : - Reflective Level

• The final level of processing is analysis and reflection of all experiences is done in reflective level.
• All experience and its meaning is stored in human brain.
• This level mainly deal with analyzing past user experiences and future requirements to plan for goal.
• Then based user preferences, we choose a methods to execute plan.

Three Level overview

• Human emotions can affect decisions. These levels can be affected by human being.
• At the visceral level we perform the method.
• Physical aspects of performing the task can be considered.
• Human senses of vision, hearing, smell, touch and taste are used to perceive human actions.

Explain How Colours Play Major Role in Human Interface Design

Q.Explain How Colors Play Major Role in Human Interface Design (DEC 17) 10M

Q.Short note on: Colors(DEC 16) 5M

Ans - Colors play an important role in adding dimensions, reality and life to the screen vision.

Proper utilization of colors would help the user to discriminate between different objects or components on the screen and make the display more interesting to look at.

It also helps in emphasizing the logical constitution of the information.

Uses of colors

• Colors must be used to support formatting of content on the screen. It plays an important role when the screen has to present humongous amount of information to be easily readable.
• Colors are used to identify logical structure of ideas, processes, and sequences.
• Colors can also enhance screen appeal.

Choosing colors:

Following factors should be considered for choosing colors:

• Problems arising due to colors that effect the human visual system
• Environment in which the colors will be displayed and viewed
• The task user is performing
• The way colors will be used
• The physical hardware through which colors will be displayed.

Colors add more meaning to the product categories, emphasis important information, and provide context.

Common color meanings:

Actions and warnings are mostly presented in warm colors - Red, orange, yellow.

Background information usually cool - Green, blue, violet, purple

Some common color associations are given in table below:

Warm colors :  Action, response required, spatial closeness

Cool colors :  Status, background information, spatial remoteness

Mental Model

Q. Short Note on: Mental Model (DEC 16 / DEC 17) 5M

Ans -

1. Mental models are representations of systems and environments derived from experience.
2. People understand and interact with systems and environments by comparing the outcomes of their mental models with the real-world systems and environments.
3. When the outcomes correspond a mental model is accurate and complete. When the outcomes do not correspond the mental model is inaccurate or incomplete.
4. With regards to design there are two basics of mental models: mental models of how systems work (system models) and mental models of how people interact with systems (interaction models).
5. Designers generally have very complete and accurate models but often have weak interaction models-i.e. they know much about how a system works but little about how people will interact with the system.
6. Conversely users of a design tend to have sparse and inaccurate system models, but through use and experience commonly attain interaction models that are more complete and accurate than those of designers.
7. Optimal design results only when designers have an accurate and complete system model attain an accurate and complete interaction model and then design a system interface that reflects an efficient merging of both models.
8. Designers can obtain accurate and complete interaction models through personal use of the system, laboratory testing and direct observation of people interacting with the system or similar systems.
9. Use of the system by the designer will reveal obvious design problems but will fail to reveal the problems of interaction that emerge when people are unfamiliar with the system.
10. Laboratory testing is useful for evaluating designs in a controlled environment but most conducted with care as the artificial context and expectation effects can compromise the validity of the results.
11. Direct observation in the target environment is the preferred method for acquiring accurate information about how people interact with systems but is costly and impractical for designs that are not yet publicly available.
12. Design with people’s interaction model in mind. If there is a standard mental model for how something works, try to design leveraging that model.
13. When this is not possible create an interaction experience that draws from common mental models as much as possible such as the desktop metaphor for computers.
14. However, do not contrive design just to leverage a familiar model it is better to have people learn a new model that is clear and consistent than to use a familiar model that does not fit.

Quantitative Research

Q. Short Note on: Quantitative Research (DEC 16) 5M

Ans- Quantitative research methods emphasize objective measurements and the statistical, mathematical, or numerical analysis of data collected through polls, questionnaires, and surveys, or by manipulating pre-existing statistical data using computational techniques. Quantitative research focuses on gathering numerical data and generalizing it across groups of people or to explain a particular phenomenon.

Quantitative research deals in numbers, logic, and an objective stance. Quantitative research focuses on numeric and unchanging data and detailed, convergent reasoning rather than divergent reasoning [i.e., the generation of a variety of ideas about a research problem in a spontaneous, free-flowing manner].

Its main characteristics are:

• The data is usually gathered using structured research instruments.
• The results are based on larger sample sizes that are representative of the population.
• The research study can usually be replicated or repeated, given its high reliability.
• The researcher has a clearly defined research question to which objective answers are sought.
• All aspects of the study are carefully designed before data is collected.
• Data are in the form of numbers and statistics, often arranged in tables, charts, figures, or other non-textual forms.
• The project can be used to generalize concepts more widely, predict future results, or investigate causal relationships.
• The researcher uses tools, such as questionnaires or computer software, to collect numerical data

State the goals of Distributed System. (December 2016) (5 Marks)

Q. State the goals of Distributed System. (December 2016) (10 Marks)

Ans -  Following are the goals of distributed system:

1. Resource sharing: sharing hardware, software, and data 
2. Openness: openness of main interface of the system, scalability of the current system 
3. Concurrency: concurrent execution of the processes, high performance, optimum rate of price and performance
4. Fault tolerance: ability to tolerate the fault of system units, availability (using potential redundancy to overcome the system fault).
5. Transparency: a distributed system can be looked as one computer (access transparency, position transparency, parallel transparency,....)
6. Scalability: can solve larger problems without larger computers
7. Openness and heterogeneity: applications and data may be difficult to relocate and reconfigure

Discuss Raymond Tree Based Algorithm of token based distributed mutual exclusion. (May 17 / Dec 16) (10 Marks)

Q. Discuss Raymond Tree Based Algorithm of token based distributed mutual exclusion. (May 17 / Dec 16) (10 Marks)

Ans -  Raymond’s tree based algorithm is lock based algorithm for mutual exclusion in a distributed system in which a site is allowed to enter the critical section if it has the token. In this algorithm, all sites are arranged as a directed tree such that the edges of the tree are assigned direction towards the site that holds the token. Site which holds the token is also called root of the tree.

Data structure and Notations

Every site Si keeps a FIFO queue, called request_q

This queue stores the requests of all neighboring sites that have sent a request for the token to site Si but have not yet been sent token. A non-empty request_q at any site indicates that the site has sent a REQUEST message to the root node.

Every site Si has a local variable, called holder 

This variable points to an immediate neighbor node on a directed path to the root node.

 

Algorithm

To enter Critical section:

1. When a site Si wants to enter the critical section it sends a REQUEST message to the node along the directed path to the root, provided it does not hold the token and its request_q is empty. After sending REQUEST message it add its request to its request_q.
2. When a site Sj on the path to the root receives the REQUEST message of site Si, it places the REQUEST in its request_q and sends the REQUEST message along the directed path to the root, if it has not sent any REQUEST message for previously received REQUEST message.
3. When the root site Sr( having token) receives the REQUEST message, it sends the token to the requesting site and sets its holder variable to point at that site.
4.  On receiving the token, Site Sj deletes the top entry from its request_q and sends the token to the site indicated by deleted entry. holder variable of Site Sj is set to point at that site.
5.  After deleting the topmost entry of the request_q, if it is still non-empty Site Sj sends a REQUEST message to the site indicated by holder variable in order to get token back.

To execute the critical section:

1. Site Si executes the critical section if it has received the token and its own entry is at the top of its request_q.

To release the critical section: 

After finishing the execution of the critical section, site Si does the following:

1.  If its request_q is non-empty, then it deletes the top most entry from its <request_q and then it sends the token to that site indicated by deleted entry and also its holder variable is set to point at that site.
2. After performing above action, if the request_q is still non-empty, then site Si sends a REQUEST message to the site pointed by holder variable in order to get token back