User
Requirements - The user will provide informal statements that must be
transformed into the language of engineering and the design process. These are
often a mix of goals, functions, means, constraints, and specifications.
Objectives - Objectives, or design goals, are the desired attributes of the design, what the design will "be" and what qualities it will have. They are often adjectives and characterized by present participles such as "are" and "be." Ideally, they are separated into primary and secondary objectives. Objectives allow exploration of the design space to select amongst alternatives that are at least acceptable or satisfice.
Constraints - Constraints are strict limits that a design must meet in order to be acceptable. They limit the size of the design space.
Metrics - Metrics measure how well the objectives are met.
Functions - Functions are often expressed as verb-object pairs. They describe what the design (or, more likely, an object within the design) will "do" or accomplish, with an emphasis on input-output transformations.
Specifications - Specifications measure how well the functions must perform.
Means - Means, or implementations, are methods of executing or realizing the functions that the design must perform. They represent specific design choices.
Attributes List - An attributes list identifies desired attributes of the design and can be used as a precursor to identifying objectives.
Objectives List or Tree - A hierarchical objective tree or indented objective list provides a mechanism for all interested parties (designers and client) to visualize the scope of the project and perceived priorities. Traversing down the tree towards sub-objectives tends to answer the question of "how" a design will accomplish specific objectives, while moving upwards towards the root addresses "why" a particular objective is important. For convenience, constraints may also be listed on the tree using a different shape.
Pairwise Comparison Chart (PCC) - A PCC is used to prioritize goals. Rows and columns are labeled with goals and each element of the table, other than the diagonal, is filled with a 1 or a 0, depending upon whether the row goal or the column goal is more important. Elements are then summed horizontally and a higher score indicates higher priority.
Numerical
Evaluation Matrix (NEM) - A NEM is used to compare design alternatives.
Columns list conceptual design approaches and rows list constraints and
objectives, with the latter weighted by priority from the PCC. Entries within
the matrix are metrics, estimates of how well the objective is met by a certain
approach. The metric (0-100%) is multiplied by the weight to produce a score,
and the scores totaled by column to identify the best design approaches.
Constraints are used to eliminate design approaches.
Black Box & Transparent Box Diagrams - A black box is a graphical representation of a design, illustrating inputs, outputs, and the transformations between them. The "cover" of a particular black box may then be lifted (made transparent), exposing additional detail about the I/O and internal structure of the black box.
Morphological Chart - Used to visualize the size of the design space. Desired features or functions are listed on rows with columns corresponding to competing designs. Entries
describe the means by which a particular design approach will realize the function.
Function-Means Tree - Used to illustrate primary and secondary design functions and possible means. Functions are represented as rectangles and possible means as trapezoids. Hierarchical in nature, with certain functions (or means) requiring secondary functions.
Selection Matrix - A method for evaluating competing approaches with respect to objectives. Rows list design constraints and objectives, while columns list design alternatives. Entries estimate how well a particular approach will achieve an objective.
House of Quality - Also known as a Quality Function Deployment (QFD). Displays and relates stakeholder interests, desired attributes, metrics, targets, and current products or competing designs.
Work Breakdown Structure (WBS) - A WBS illustrates the breakdown of tasks, either as a hierarchical tree, or as an indented list. It must possess two properties: (1) the WBS must be complete in that it accounts for all tasks that consume resources; and (2) the WBS must be adequate in that the resources needed to execute a task can be accurately estimated. The WBS typically does not identify the time or personnel associated with tasks. However, depending upon the organization of the WBS, sub-tasks may be grouped by discipline.
Linear Responsibility Chart (LRC) - An LRC lists team members as columns and identified tasks as rows. Each entry indicates a specific member's role in performing a specific task, be it primary responsibility, advisory, approval, etc. The tasks match those identified in the WBS.
Percent Complete Matrix (PCM) - Rows are associated with required tasks. Columns indicate expected duration, percent completed, and status.
Activity-On-Node (AON) Network - Illustrates relationships between tasks. Each task is assigned a node and dependencies are indicated with various lines.
Gantt Chart - A Gantt chart shows time on the horizontal axis and tasks from the WBS on the vertical axis. Rectangular bars indicate the duration of specific tasks and symbols may be included to identify important points in time (e.g., start, critical point). Colors may be used to indicate variable start times or critical tasks. If not too complicated, arcs may be added to indicate dependencies, similar to an AON network.
Failure Modes, Effects, and Criticality Analysis (FMECA) - A FMECA ranks failure modes, based upon severity, probability of occurrence, and detection probability. The first step is to identify all possible failure modes and classify them according to severity. The second step is to determine the probability of occurrence. For electronics, this may be based on MTBF calculations. The third step is to determine the probability of detection. This may be based upon the severity or upon the test plan and diagnostic capabilities. These three rankings are then multiplied together to form a Risk Priority Number (RPN).