Clarifying Design Objectives.

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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
  designs 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 asiderecorded, but not discardedto
  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 clients 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 gt
• A gt B means A is preferred to B.
• Eg 1 preferred A gt B gt C, 4 preferred B gtC gt A,
  3 preferred C gt B gt 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 gt B gt 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 MetricsAn 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