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Lab 3.5 Exercises

3.5.1. Define the Task Analysis Process

a) What is the difference between a task and a function provided by a software package? Why is the difference important?




Answer: Tasks include the goal of the human users and criteria for success, whereas functions relate simply to the features built in to software to carry out the specific actions of the task.

Perhaps the more important reason to understand the difference is that each is dealing with a different level of the software. The task is typically what the user sees, such as wanting to send an email message to someone else. How that task is carried out is not important.

On the other hand, developers are concerned with the specific actions. In the case of sending an email message, they not only need to provide functions for composing the message, but also interacting with the network and dozens of other functions.

3.5.2. Carry Out a Task Analysis

a) What is the output of a hierarchical task analysis?




Answer: A hierarchy of subtasks. This hierarchy helps designers visualize the whole task and allows optimizations to be identified such as common subtasks, inconsistent ordering of tasks, and a measure of complexity to be calculated.

This aspect should not be underestimated. By breaking down the “big task” into smaller ones, you gain yourself a great number of advantages. First, design is generally easier. You need simply address the issue involving that one task, its interaction with the user, interaction with other tasks, and so forth.

For example, considering sending an email message. If you provide the functionality to save a draft copy of the message to come back to later, you need some mechanism to store in on the hard disk. If you consider this task along with the others, such as saving email that you have received, you may assume that you need an interface to save the draft message. However, considering this task separately, you might see that there is no need for an interface (other then perhaps a button “Save draft”). Like Netscape Communicator, drafts of messages are stored in the same manner as incoming and sent messages so an extra interface is not needed.

Another aspect involves testing. You can test the individual components to ensure that they would as an entity. Once you have verified this, it is easier to ensure the individual components work together.

b) How do actions and objects help us to perform a task analysis?




Answer: They help in the first level of decomposition of tasks, and help establish a terminology for communication between users and designers

c) Take communication as an element of a task you need to analyze. Come up with a list of actions to take and objects which need to be accessed or manipulated. Discuss the steps necessary to analyze this task.




Answer: You may end up with something like Table 3.9.

Having identified actions and objects, we can proceed to combine them in meaningful ways to define tasks. One example might be:

Task: Create/message/on a medium/with a text header/with a text body/to a receiver/at an address/with a device

Once you have identified the specific task, you need to describe the task in as much detail as possible and identify dependencies this task has with other tasks. Along with this you need to identify problems the users have with the current conditions (in order to identify specific areas to address) as well as how the solution to the task is expected to perform. The performance criteria can be anything from specific behavior the software must exhibit to speed or efficiency issues.

Table 3.9. Actions and Objects
send (forward, post, mail, notify, reply)sender (person id, group id)
create (write, draw, speak)receiver (mailbox, board, pigeonhole)
perceive (read, notice, identify)address (postcode, login, room)

media (notepad, memo)

header (title, sender, address)

device (pen, typewriter)

body (text, graphics)

From such a brief description, you can flesh out the task description using a template such as:

  1. Task Intrinsics

    • Identify task uniquely

    • Inputs and outputs

    • Transformational process

    • Terminology

    • Equipment

  2. Task Dependency

    • Dependency on other tasks

    • Critical effects

  3. Current User Problems

    • Performance problems

  4. Performance Criteria (if any)

Once the full list of tasks is obtained, the next two substages can be actioned. Relationships between tasks can be identified. Users can be asked to rank the tasks in order of importance and frequency. Such a ranking is useful in the later analysis stages when simplification and complexity are being considered. More analysis effort can be placed on the tasks at the head of the rankings.

Arranging tasks and subtasks in hierarchies is a very old technique but still effective as a visualization tool for the designer. The apparently simple task of making tea is shown in Figure 3.5. The hierarchy shows ten subtasks and shows some complexity with scope for a large number of different orderings. Some readers will use quite a different sequence for their tea making. Nevertheless, this technique provides a useful visualization that allows users and designers to converse in a common way about the nature of a task.

Figure 3.5. Tea Making Task Hierarchy

To perform the task analysis we examine the task descriptions for certain characteristics and patterns:

  • Alternative decompositions of a single task

  • Common tasks occurring at different points

  • Multiple orderings of subtasks

  • Parallel operation with multiple controls

  • Categorization by complexity, i.e., number of levels of subtask

These processes are made easier or more difficult depending on whether the task description notation is textual or graphical. Task analysis tools can help here, too.



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