Docstoc

lyle.smu.edusys7301Fall0005_dsgn.ppt

Document Sample
lyle.smu.edusys7301Fall0005_dsgn.ppt Powered By Docstoc
					              Agenda for design activity
            1. Tracing requirements
            2. Managing requirements
            3. Requirements management tools
            4. Homework




5. Design                                       1
            1. Tracing requirements
              Types of tracing
              Complexity of tracing
              Reasons for tracing
              Observations
              Suggestions




5. Design          1. Tracing requirements   2
             Types of tracing (1 of 2)



    Req            Req            Req              Req               Req


   Design          Design               Design            Design    Design


    Req      Req            Req          Req               Req


  Straight     Expansion                 Focus           Creation    End
  through


                       Five types of tracing

5. Design                1. Tracing requirements                           3
             Types of tracing (2 of 2)
No hazardous material     Calculation      Graphing         Missile

        Design                       Design                 Design

No hazardous material              Spreadsheet          Instrumentation
   Straight through                   Focus                 Creation

                      Weight                Bedroom on east side

                       Design                     Design

            Weight A            Weight B      Building supplies
                      Expansion                       End

5. Design
                      An example of each type                          4
            Complexity of tracing (1 of 2)
            Often used in tracing and tracing


                                 Spec




                    Spec                       Spec


              Simple tracing flows from spec to spec
              and doesn’t include tracing to design.
                  It’s the more common practice
5. Design                  1. Tracing requirements     5
            Complexity of tracing (2 of 2)
More complex but provides truer tracing picture
                                    Spec         contract

    Design of the higher product                   Stakeholders
                                    Design


            contract     Spec          I/F         Spec     contract

  Stakeholders                                               Stakeholders
                        Design                    Design

               Note: Flow within a rectangle or ellipse not shown

   Flow through design is more complex and is a less
 common practice. However, it produces less problems
5. Design                    1. Tracing requirements                    6
            Reasons for tracing (1 of 5)
 Reason 1: tracing -- Where did requirement
  get implemented?
   • Less precise linkage criteria than tracing
     for verification/validation
   • Often done by doing tracing first




5. Design           1. Tracing requirements       7
            Reasons for tracing (2 of 5)
Reason 2: tracing for verification/validation --
 What lower requirements are used in
 verifying/validating higher requirements?
  • Simplest and most repeatable




5. Design           1. Tracing requirements         8
            Reasons for tracing (3 of 5)
Reason 3: tracing for origin -- Where did each
 requirement come from; why does it exist?
  • more linkages to explain how design
    creates requirements




5. Design           1. Tracing requirements       9
            Reasons for tracing (4 of 5)
 Reason 4: tracing for change impact -- If one
  requirement changes, what other
  requirements must change?
   • More linkages to reflect impacts of
     requirements on each other




5. Design           1. Tracing requirements       10
            Reasons for tracing (5 of 5)
  The four different reasons for tracing can
   result in four different sets of linkages




5. Design           1. Tracing requirements     11
            Observations (1 of 4)
Tracing is a best practice
  • Supports verification and validation
  • Makes sure requirements are implemented
  • Prevents unnecessary requirements
  • Shows how changing one requirement
    changes others
  • Meets customer expectation




5. Design       1. Tracing requirements       12
            Observations (2 of 4)
   Tracing is expensive
     • Tracing is complex and expensive;
       $benefit/$cost > 1?
     • Many believe cost far out weighs the
       benefit; takes time, diverts resources,
       degrades engineers, and drives tools
     • Lack of training & rules make trace not
       repeatable or dependable




5. Design         1. Tracing requirements        13
            Observations (3 of 4)
 The following rules-of-thumb can cause
  trouble
   • All requirements must come from
     somewhere
   • All requirements must go somewhere
   • All requirements shall trace in one direction
   • Tracing shall be from spec to spec and not
     within a spec
   • Tracing shall not be from spec to design
   • There shall be one “shall” per requirement
   • All requirements shall be individually traced
5. Design        1. Tracing requirements        14
            Observations (4 of 4)
 Design is an essential part of flowdown and
  trace
 Design is difficult to capture in requirements
  management tools
 Few people use trace to understand the
  effect of a requirement change on other
  requirements




5. Design        1. Tracing requirements           15
            Suggestion (1 of 3)
 Set customer expectations
 Negotiate with customer to minimize effort
  for design and verification
 Document agreements -- in the spec if
  possible using clarifications, definitions, and
  examples




5. Design         1. Tracing requirements           16
            Suggestion (2 of 3)
Choose a type of tracing such as tracing to
 confirm verification and validation
Provide rules and training
Provide for independent confirmation of
 tracing




5. Design       1. Tracing requirements        17
               Suggestion (3 of 3)
                   Req              Req             Req

Expansion
                   Design                 Design           Focus

             Req            Req             Req



                     Req              Req            Req

 Expansion                                                  Focus


              Req             Req             Req


Flow expansion and focus through design -- not directly
5. Design                1. Tracing requirements                    18
            2. Managing requirements
            Requirements attributes
            Data interface attributes
            Physical interface attributes
            Documenting requirements
            Managing requirements change




5. Design            2. Managing requirements   19
       Requirements attributes (1 of 2)
 Requirement -- text
 Title -- short text
 Numerical identifier -- added by management
  tool
 Product unique identifier (PUI) -- added by
  engineers
 Verification method -- how requirement
  verified




5. Design         2. Managing requirements      20
       Requirements attributes (2 of 2)
   Owner -- person responsible for success
   Stakeholders -- people with an interest
   Change history -- change dates
   Flowdown/traces -- flowdown and trace
    links
   Rationale -- why requirement is the way it is




5. Design          2. Managing requirements         21
            Data interface attributes
               Data item
               Criteria
               Timing
               Units and enumeration
               Format
               Ranges
               Accuracy




5. Design           2. Managing requirements   22
  Physical interface attributes (1 of 2)
            Electrical
             • Signals
             • Power
             • EMI/EMC
             • Grounding




5. Design     2. Managing requirements     23
  Physical interface attributes (2 of 2)
              Mechanical
               • Dimensions
               • Mounting
               • Alignment
               • Weight
               • Heating
               • Cooling




5. Design      2. Managing requirements    24
            Documenting requirements
               Media
                 • Paper
                 • Office computer tools
                 • Data base
               Format
                 • Contractor chosen
                 • Commercial standard
                 • MIL-STD-490A
                 • MIL-STD-490B


5. Design           2. Managing requirements   25
       Managing requirements change
            Often handled through
             configuration management
            Techniques
              • Data base
              • Change pages
              • Red-line changes




5. Design          2. Managing requirements   26
 3. Requirements management tools
   INCOSE tools survey
   INCOSE tool-selection criteria
   Tools surveyed by INCOSE
   Selection considerations for ease of use
   Selection considerations for compatibility
   Selection criteria for satisfaction




5. Design     3. Requirements management tools   27
            INCOSE tools survey
  Comparison made by National Council on
   Systems Engineering (INCOSE)
  Internet address:
   http\\www.incose.org/workgrps/tools/req_su
   rv.htm




5. Design     3. Requirements management tools   28
INCOSE tool-selection criteria (1 of 2)
      1. Capturing requirements identification
      2. Capturing system element structure
      3. Requirements flowdown
      4. Traceability analysis
      5. Configuration management
      6. Documents and other output media




5. Design       3. Requirements management tools   29
INCOSE tool-selection criteria (2 of 2)
            7. Groupware
            8. Interfaces to other tools
            9. System environment
            10. User interfaces
            11. Standards
            12. Support and maintenance
            13. Other features




5. Design       3. Requirements management tools   30
    Tools surveyed by INCOSE (1 of 2)
            Cadence -- Bones
            Boeing North American, Inc. --
             CASETS
            Vitech -- CORE
            Mesa Systems Guild -- Cradle/SEE
            Zycad -- DOORS
            Teknowledge -- ProductTrack
            Image That -- Extend
            Ascent Logic -- RDD-100
            Integrated Chipware Inc. -- RTM
            TD Technologies -- SLATE
5. Design          3. Requirements management tools   31
    Tools surveyed by INCOSE (2 of 2)
     Cadence -- SPW
     Compliance Automation -- VITAL LINK
     Teledyne Brown Engineering -- XTie-RT
     Nu Thena Systems -- Foresight
     MathWorks -- MATLAB, Simulink,
      Stateflow, Real-Time Workshop
     Rational (Requisite) -- RequisitePro V2.0
     Statemate -- Magnum



5. Design       3. Requirements management tools   32
      Considerations for ease of use
   Using
   Learning
   Putting information into the tool
   Extracting information from the tool
   Knowing what information is in the tool
   Navigating among information
   Grouping information for comparison and
    reports
   Assuring quality such as spell checking


5. Design     3. Requirements management tools   33
      Considerations for compatibility
   Computer and operating system being
    used on the project
   Way team members work




5. Design     3. Requirements management tools   34
        Considerations for satisfaction
   Gain understanding of the tool before
    committing to use tool
   Avoid choices based on demo by sales
    person




5. Design      3. Requirements management tools   35
             4. Homework
            Diagram
            Customer wants
            Timepiece spec
            Timepiece contract
            Design
            Clock spec
            AC adapter spec
            Problem



5. Design        4. Homework      36
                          Diagram
                          Customer wants
                            C1, C2, C3


     Timepiece contract   Timepiece spec
            X1                  S1


                                            Timepiece design
                                            D1, D2, D3, D4, D5




                  Clock spec             Adapter spec
                      T1                   U1, U2

5. Design                  4. Homework                           37
               Customer wants
   C1: I want a timepiece that I can look at
    and determine time accurate to one
    minute per day since the last setting
   C2: Cost, size, weight, mechanism, style,
    power, and everything else are of no
    consequence
   C3: I will give a flat $100 for the timepiece
    regardless of design




5. Design             4. Homework                   38
              Timepiece spec
   S1: The timepiece shall display time
    accurate to one minute per day since the
    last setting




5. Design           4. Homework                39
            Timepiece contract
   X1: Customer will pay $100 for timepiece
    meeting timepiece spec




5. Design           4. Homework                40
              Design (1 of 2)
D1: I’ll design the timepiece using existing
 components.
D2: I want to make a lot of profit
D3: The Dilmore catalogue shows that its least
 expensive clock is the model 100 for $4. It is
 resettable to correct the time, is accurate to
 one minute per day since the last setting, but
 requires an AC adapter




5. Design           4. Homework               41
                Design (2 of 2)
   D4: The Hazel catalog shows the model
    200 as its least expensive AC adapter
    compatible with the Dilmore model 100
    clock, and the adapter costs $1.
   D5: The model 200 AC adapter comes in
    either black or beige at no extra cost. In
    my opinion, beige is more attractive in the
    customer’s environment




5. Design            4. Homework                  42
                 Clock spec

   T1: Clock shall be a Dilmore model 100
    clock




5. Design           4. Homework              43
              AC adapter spec

    U1: AC adapter shall be a Hazel model 200
     AC adapter
    U2: AC adapter shall be beige




5. Design            4. Homework                 44
               Problem (1 of 4)
   1. What items need to be successfully
    implemented to verify item D5? -- a. T1, U1,
    & U2; b. U1 & U2; c. U1; d. U2
   2. For tracing purposes, what items
    implement item X1? -- a. D3; b. D4, c. D3 &
    D4; d. D3, D4, & D5




5. Design            4. Homework                   45
               Problem (2 of 4)
   3. For tracing purposes, where did the
    requirements for item D4 come from? -- a.
    D3; b. D1, D2, & D3; c. D1, D2, D3, & X1; d.
    S1, D1, D2, & D3
    4. For tracing purposes, what items
    implement item C2? -- a. none of the listed
    items, b. S1 & X1, c. D1, D2, & D3; d. T1,
    U1, & U2




5. Design            4. Homework                   46
              Problem (3 of 4)
5. What items need to be successfully
 implemented to verify item S1? -- a. C1; b. D3; c.
 D2 & D3; d. D3, D4, & D5
6. For tracing purposes, where does item D1
 come from? -- a. none of the listed items; b. S1;
 c. X1; d. S1 & X1




5. Design            4. Homework                47
              Problem (4 of 4)
   7. For tracing purposes, where does item
    U2 come from? -- a. none of the listed
    items; b. D5; c. D4; d. S1
   8. If item D3 were to change to no longer
    require an AC adapter, which items would
    change? -- a. no items would change; b.
    D4; c. D4 & U1; d. D4, D5, U1, & U2




5. Design           4. Homework                 48

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:5/8/2013
language:English
pages:48