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Overcoming Customer Constraints on Requirements Documents
Overcoming Customer Constraints on Requirements Documents
Presented by:Robert Smole
Presented by:Robert SmoleNovember 5, 2008November 5, 2008
Sub-Optimization of Systems Engineering
Sub-Optimization of Systems Engineering
2
AgendaAgenda
• Introduction
• Problem
• Approach
• Results
• Wrap Up
• Introduction
• Problem
• Approach
• Results
• Wrap Up
3
IntroductionIntroduction
• Systems Engineering– Means to enable the realization of
successful systems – best practices– Considers both the business and the
technical needs of all customers - constraints
• What happens when the ‘business needs’ constrain the ‘best practices’?
• Systems Engineering– Means to enable the realization of
successful systems – best practices– Considers both the business and the
technical needs of all customers - constraints
• What happens when the ‘business needs’ constrain the ‘best practices’?
4
Why Sub-Optimal?Why Sub-Optimal?
• Find a balance.
• Approach: Sub-optimal SE.
• Agenda: Communicate the value of SE.
• Goal: …to realize a successful system.
• Find a balance.
• Approach: Sub-optimal SE.
• Agenda: Communicate the value of SE.
• Goal: …to realize a successful system.
SystemsEngineering
Best Practices
CustomerConstraints
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Size: Length-1092ft, Weight-97,000tonsCost: Approx. $5-6 Billion Construction time: 6-7 years Design time: Approx 6 years from Concept
A mobile, nuclear powered, survivable, A mobile, nuclear powered, survivable, sea-based super structure, capable of sea-based super structure, capable of accommodating approx 5000 accommodating approx 5000 personnel, managing 75+ air combat personnel, managing 75+ air combat vehicles, and conducting joint vehicles, and conducting joint operations. operations.
Nimitz Class CVN
HIGHLY COMPLEX AND CHALLENGING PROGRAMS DEMAND SYSTEMS ENGINEERINGHIGHLY COMPLEX AND CHALLENGING PROGRAMS DEMAND SYSTEMS ENGINEERING
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Requirements Analysis
Requirements Model
R
Functional Analysis• Define high level FA from ORD• Define mission/operational performance• Decompose functions to lowest level• Allocate performance requirements to functions
• Develop FFBDs• Develop Operational Threads (sortie)
Operational Scenarios,Conceptual Behavior Models
F1 F5
F2 F3
F4
Physical ArchitectureAnalysis
• Define System Structure• Define Internal/External Interfaces • Determine Island Alternatives• Establish product baselines• Define system design constraints• Allocate functions to systems/components
Common Island Component Models
Components
Interfaces
System
• Analyze Design & Assess Risk• Cost Assessment• Conduct trade studies• Select Best Design Solution• Automatic Document Generation• Provide Metrics Reports
Product Evaluation and Document Generation
Analysis ResultsSRDs
• Determine common missions• Review top level requirements documents• Decompose ORD• Derive Ship system Requirements• Flowdown to system requirements•Derive Functional / Performance Requirements
R2R1
R1-1
NGSB-NN: Model-Based SE ApproachNGSB-NN: Model-Based SE Approach
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Does our system as-designed and as-built meet the system requirements as-validated?
Verification
Develop Physical Solution
Develop Functional Solution
Perform Requirements Analysis
Requirements ProcessRequirements Process
Does the customer agree with our
interpretation of the requirements?
Validation
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ProblemProblem
• Update a System Requirements Document
• Not configuration managed within the CASE tool.
• Contained some or all of: “will”, “shall”, “may”, & “should” within requirement text.
• Requirements within functional statements.
• Requirements not singular (more than one “shall”).
• Requirements not “stand alone”.– Definitions within the body of the document, not in appendix.– SRD used an outline format - multiple indents.
• Interface requirements not mapped to interfaces on diagram.
• Update a System Requirements Document
• Not configuration managed within the CASE tool.
• Contained some or all of: “will”, “shall”, “may”, & “should” within requirement text.
• Requirements within functional statements.
• Requirements not singular (more than one “shall”).
• Requirements not “stand alone”.– Definitions within the body of the document, not in appendix.– SRD used an outline format - multiple indents.
• Interface requirements not mapped to interfaces on diagram.
9
Communicate FunctionCommunicate Function
Function1
Function2
Communicate Orders 3
Function4
Function5
AND AND
10
Improper Use of the CASE ToolImproper Use of the CASE Tool
Function1
Function2
Communicate Orders 3
Function4
Function5
Requirement(s) Requirement(s) Requirement(s)
Requirement(s) Requirement(s)
Liabilities: Traceability, Verification, Decomposition
11
Requirements Imbedded within FunctionsRequirements Imbedded within Functions
3.1.3 Communicate Orders1) The _____ subsystem shall be the primary means of
communicating orders. 2) The _____ subsystem with interfaces to the _____ shall provide
supplementary communications.a) Main Deck Communications Capability
1) The _____ subsystem shall be the primary means of communication for the coordination of operations on the Main Deck.
2) The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
b) 2nd Deck Communications Capability1) The _____ subsystem shall be the primary means of
communication for the coordination of operations on the 2nd Deck.
2) The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
c) Engine Room Communications Capability1) The _____ subsystem shall be the primary means of
communication for the coordination of operations in the Engine Room.
2) The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
3.1.3 Communicate Orders1) The _____ subsystem shall be the primary means of
communicating orders. 2) The _____ subsystem with interfaces to the _____ shall provide
supplementary communications.a) Main Deck Communications Capability
1) The _____ subsystem shall be the primary means of communication for the coordination of operations on the Main Deck.
2) The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
b) 2nd Deck Communications Capability1) The _____ subsystem shall be the primary means of
communication for the coordination of operations on the 2nd Deck.
2) The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
c) Engine Room Communications Capability1) The _____ subsystem shall be the primary means of
communication for the coordination of operations in the Engine Room.
2) The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
12
ConstraintsConstraints
• The overall document format and layout had to remain consistent with the original document which was not consistent with standard SRD formatting.
• Definitions and lead-in statements had to remain in their relative location (could not move the definitions to an appendix).
• “May” was acceptable - there are some design targets that are not ‘hard’ requirements (they don’t have to meet these).
• The overall document format and layout had to remain consistent with the original document which was not consistent with standard SRD formatting.
• Definitions and lead-in statements had to remain in their relative location (could not move the definitions to an appendix).
• “May” was acceptable - there are some design targets that are not ‘hard’ requirements (they don’t have to meet these).
13
ApproachApproach
• Moved all the ‘requirements’ from Word to Excel.
• Parsed the ‘requirements’ from the functions.
• Separated multiple shall statements. (singular requirements)
• Placed definitions in Requirement Objects and marked the Verification Method as ‘n/a’ to identify it as ‘not a requirement’.
• Standardized on the use of “shall” to denote requirements.
• Moved all the ‘requirements’ from Word to Excel.
• Parsed the ‘requirements’ from the functions.
• Separated multiple shall statements. (singular requirements)
• Placed definitions in Requirement Objects and marked the Verification Method as ‘n/a’ to identify it as ‘not a requirement’.
• Standardized on the use of “shall” to denote requirements.
14
ApproachApproach
• Allowed the use of “may” for design targets (these are not requirements).
• Used the spreadsheet to provide a comparison to the baseline.
• Decided on an iterative approach to ‘fix’ the SRD.– Further changes to structure (ie, interface linking) in
future revisions.
• Migrated requirements to the CASE Tool (Cradle) and used this tool to generate the Rev B SRD.
• Allowed the use of “may” for design targets (these are not requirements).
• Used the spreadsheet to provide a comparison to the baseline.
• Decided on an iterative approach to ‘fix’ the SRD.– Further changes to structure (ie, interface linking) in
future revisions.
• Migrated requirements to the CASE Tool (Cradle) and used this tool to generate the Rev B SRD.
15
Result (example)Result (example)
3.1.3 Communicate OrdersThis function communicates orders
a) Communicate Orders - 1The _____ subsystem shall be the primary means of communicating orders.
b) Communicate Orders - 2The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
c) Main Deck Communications Capability - 1The _____ subsystem shall be the primary means of communication for the coordination of operations on the Main Deck.
d) Main Deck Communications Capability - 2The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
e) 2nd Deck Communications Capability - 1The _____ subsystem shall be the primary means of communication for the coordination of operations on the 2nd Deck.
………
3.1.3 Communicate OrdersThis function communicates orders
a) Communicate Orders - 1The _____ subsystem shall be the primary means of communicating orders.
b) Communicate Orders - 2The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
c) Main Deck Communications Capability - 1The _____ subsystem shall be the primary means of communication for the coordination of operations on the Main Deck.
d) Main Deck Communications Capability - 2The _____ subsystem with interfaces to the _____ shall provide supplementary communications.
e) 2nd Deck Communications Capability - 1The _____ subsystem shall be the primary means of communication for the coordination of operations on the 2nd Deck.
………
16
Communicate Function - RevisitedCommunicate Function - Revisited
Function1
Function2
Communicate Orders 3
Function4
Function5
AND AND
17
Proper Use of the CASE ToolProper Use of the CASE Tool
Function1
Function2
Communicate Orders 3
Function4
Function5
Requirement(s) Requirement(s) Requirement(s)
Requirement(s) Requirement(s)
Allows: Traceability, Verification, Decomposition
18
Wrap UpWrap Up
• Considerations– New Design? – Roll-over Design?– Commercially Available Products?– Integrating Other Systems?– System Complexity?
• Essentials– Interface Requirements.– Traceability.– Verification.
• Non-Essentials– Document Format/Layout.
• One step at a time = progress toward full SE
• Considerations– New Design? – Roll-over Design?– Commercially Available Products?– Integrating Other Systems?– System Complexity?
• Essentials– Interface Requirements.– Traceability.– Verification.
• Non-Essentials– Document Format/Layout.
• One step at a time = progress toward full SE
19