The attached narrated power point presentation explains the popular methods to list down and analyse design objectives. The material will be useful for KTU second year students who prepare for the subject EST 200, Design and Engineering.

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Clarifying Design Objectives
MEC

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Contents
• Definitions.
• List of Objectives.
• Pruned List of Objectives.
• Objective Tree.
• Ranking Objectives.
• Pairwise Comparison Chart.
• Aggregate Rank Ordering.
• Establishing Objectives.

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Definitions
• Objective : a feature or behavior that the
design should have or exhibit.
• Constraint : a limit or restriction on the
design’s behaviors or attributes, designs
that violate these limits are unacceptable.
• Function : a specific thing a designed
device or system is expected to do.
• Means : a way or method to make a
function happen.

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Attributes of a Safe Ladder

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O – Objectives, C – Constraints, F- Functions, M – Means.
The list of desired attributes of the safe ladder has too many entries.
To be organised in a more useful way.
Uses of ladder be grouped or clustered together in some coherent way.

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Preparing a Pruned List
• Ask questions.
• Ask why we care about them?
• Why do we want our ladder to be used
outdoors?
• Why we care whether the ladder is useful?
• To be useful so that people will buy it.
• Usefulness makes a ladder marketable.

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Pruned List of Objectives

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Intended Outline of Objectives
• Thoughtful clustering of questions.
• Develop a new list that we can represent
in an indented outline.
• Comprise of hierarchies of major headings
and various levels of subheadings.
• Allows us to explore each of the higher
level objectives, in terms of sub objectives
that tell us how to realize them.
• Objectives turn us back to the original
design statement.

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Intended List of Pruned Objectives

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Intended List of Pruned Objectives
• Identifying sub objectives or ways in which
the ladder could be useful.
• “What do you mean by safe?” is answered
by two sub objectives in the cluster of
safety issues.
• The designed ladder should be both stable
and relatively stiff.

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List of Objectives
• What to do with the things that are
removed from the original list of attributes?
• Simply put aside—recorded, but not
discarded—to be picked up again later in
the process.
• Ensure that all suggestions and ideas are
captured.
• Easier to prune/throw away things than to
recapture spontaneous ideas and
inspirations.

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Objective Tree
• Information represented graphically in a
hierarchy of boxes.
• Contains an objective for the object being
designed.
• Indented outline becomes an objectives
tree.
• Graphical depiction of objectives for the
device or system.

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Objective Tree
• Root node at the top of the tree
decomposed or broken down into sub
objectives at differing levels of importance.
• Tree reflects a hierarchical structure as it
expands downward.
• Continue to parse/decompose sub
objectives until we are unable to express
succeeding levels as further
subobjectives.
• Stop when we run out of objectives and
implementations begin to appear.

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Objective Tree
• Objectives tree also gives the tree some
organizational strength and utility.
• Clusters together related sub objectives or
similar ideas.
• Useful for portraying design issues.
• For highlighting things we need to
measure.
• Objectives will provide our basis for
choosing between alternatives.
• Tree format corresponds to the mechanics
of the process that many designers follow.

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Objective Tree
• Work down an objectives tree to get more
details.
• Answers the question “How are you going
to do that?”
• Move up the tree, or further out toward
fewer indentations.
• Answers the question “Why do you want
that?”

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Objective Tree

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Constraints in Objective Trees
• Constraints sometimes added to
objectives tree.
• Present constraints in boxes differently
shaped than the objectives.
• May use italics or a different font to denote
constraints.
• Constraints are related to but are different
from objectives.

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Juice Container Design –
Customer Concerns
• Plastic bottles and containers all look
alike.
• Product to be delivered to diverse climates
and environments.
• Safety for parents whose children might
drink the juice.
• Concern about environmental issues.
• Market competition.
• Parents/teachers want children to be able
to get their own drinks.
• Children always spill drinks.

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Annotated Objectives List for
Juice Container Design

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Objective Tree for
Juice Container Design

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Measuring Objectives
• Are some objectives more important than
others?
• What are the client’s priorities?
• How will we know whether objectives have
been achieved?
• Are there measurements we could make
to compare design objectives and their
relative achievement?

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Measuring Objectives
• Needs a ruler to establish a common basis
for comparison.
• Without rulers, we cannot meaningfully
quantify assertions.
• Ruler as a measuring stick marked with a
zero and a countable number of intervals
of fixed length to establish real numbers
that represent parameters.
• Use of ordinal scales to place things in
rank order.

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Measuring Objectives
• Ask the client to set priorities.
• Ask for subjective ranking of relative
importance.
• Client may have preferences, but no
meaning in saying that one is ‘n’ times
more important than the other.

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Ranking Objectives
• Some objectives more important than
others.
• Recognize the relative importance and
measure it.
• Comparing objectives with hierarchical
restriction in mind.
• Pairwise Comparison Chart for ordering
the relative importance of objectives.
• Can order any two objectives taken as a
pair.

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Pairwise Comparison Chart
• Compare every objective with each
remaining objective individually.
• Add total scores for each objective.
• Entries in each box of the PCC determined
as binary choices (0 or 1).
• Enter 0 in the durability column if one
objective has less preference than the
other, 1 if more preference, nothing when
weighing an objective with itself, 0.5 if
valued equally.

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Pairwise Comparison Chart
Scores for each objective found by adding across each row.

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Pairwise Comparison
• Cannot drop objectives that score zeroes.
• PCC process also known as the Borda
count, is a valid way of ordering things.
• A straightforward rank ordering, or an
ordering of place in line.
• Not a strong measurement, no scale on
which we can measure the four objectives.
• Cannot claim that one is ‘n’ times more
important than the other.

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Pairwise Comparison
• Pairwise comparison, if done correctly,
preserves transitivity, will be consistent.
• PCC (or Borda count) can be used to
indicate the collective preferences of a
group of clients or of a design team.
• Use of Aggregate PCC - develop an
aggregate ranking for a group of clients,
users, or designers

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Aggregate Rank Ordering
• Different individuals produce different
individual orderings.
• Use of ranking symbol >
• A > B means “A is preferred to B”.
• Eg; 1 preferred A > B > C, 4 preferred B
>C > A, 3 preferred C > B > A.
• Collective will worked out through the
aggregated PCC.

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Aggregate Rank Ordering
• One point awarded to the winner of each
pairwise comparison.
• Number of points awarded to each
alternative by each of the rankers is
summed.
• Group consensus based on summing
determines the most important objective.

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Aggregated Pairwise Comparison
Chart
Group Consensus C > B > A, not clearly unanimous.

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Using Pairwise Comparison Chart
• PCC approach to be applied in a
constrained, top down fashion.
- objectives are compared only when at
the same level on the objectives tree.
- higher-level objectives are compared
and ranked before those at lower, more
detailed levels.

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Using Pairwise Comparison Chart
• More “global” objectives (more abstract
objectives higher up on the objectives
tree) properly understood and ranked
before we fine-tune the details.
• Rank objectives below the top level only
for the design of complex subsystems,
within large and complex systems.
• Ask whose values are being assessed
when we use a PCC.
• There could be objectives rankings that
reflect fundamental values of clients
and/or designers.

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PCC for Juice Container Design
- Company ABC

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PCC for Juice Container Design
- Company XYZ

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PCC for Juice Container Design
- Conclusions
• Subjective values show up in PCCs and,
consequently, in the marketplace!
• Company ABC was far more interested in
a container that would generate a strong
brand identity and be easy to distribute
than in one that would be environmentally
benign or appeals to parents.
• For company XYZ, the environment and
the taste preservation ranked more highly.

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Establishing Metrics
• For assessing quantitative performance
ratings on similar, consistent scales.
• Methods:
- Use-Value Analysis.
- German VDI 2225 scales.

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Establishing Metrics

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Establishing Metrics
An Example

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Establishing Metrics
- Juice Container Design

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Establishing Metrics
- Juice Container Design

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Establishing Metrics
- Juice Container Design

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Reference
• Clive L Dim, Patrick Little and Elizabeth J
Orwin, “Engineering Design, A Project
Based Introduction”, 4th Edition, Wiley,
U.S.A, 2014.

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Thank You