SysML Reference Model Definition
Model Based System Development in the Joint Strike Missile project
Svein-Erik Søgård
KDS/Missile Division
Agenda
• Introduction
– Background
– Goals for modeling
– Challenges
• Model definition
– Principles
– Walktrough of process and reference model
• Summary
– Lessons learned
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WORLD CLASS - through people, technology and dedication.
Background
• Main motivation for MBSE in JSM
– Lack of system and architecture level documentation in previous
projects
• Many documents and model fragments but not up to date, poor
value for money (waste), not systematically organized). Very hard
for
– Maintainability
– Introducing new developers
– Doing analysis (e.g. safety)
– Initiative from Management (LEAN thinking) as well as a JSM core
team of developers that would do it better
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WORLD CLASS - through people, technology and dedication.
Background
• KDS Survey that concluded with SysML and MagicDraw™ modeling tool
– Major player in MBSE
– Simultaneously evaluated UML tool for SW modeling
– smooth transition to SW development was important
• JSM project main focus so far on functional analysis & design, but also
physical architecture is addressed
• MagicDraw™ is NOT «THE System Tool»
– Used in conjunction with other tools
– Information management
• Linking other documentation rather than duplicating it
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WORLD CLASS - through people, technology and dedication.
Goals
• «Real» Model Based,
– Not only drawings and model fragments
– Consistent model with a set of well defined views
• System Model (SysML) characteristics
– Complete functional description (concise, right abstraction level)
focused on what the system shall do. Easy entry point to what the
system shall do and how it works
– Physical System Architecture that is precise and detailed about
interfaces at different levels (How the system shall be constructed)
– Specifications for component design (in other disciplines: SW, PLD
electronics, mechanics)
– Focus on maintainability (of the model and the product)
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WORLD CLASS - through people, technology and dedication.
Challenges
• Project size (JSM) is too large to be optimal
– “How to do” established later than desirable
– doing development and establishing how to model in parallell
– Too few resources to follow up new teams
• Culture (document centric, different philosophy & terminology)
– Commitment to the process and methodology
• Commitment from engineers are even more important than
commitment from management
– developers tend to fall back to «their old methods» when they get
pressed for time
• SysML is a complex language. Requires time to understand what to use
and how to use it to make consistent models.
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WORLD CLASS - through people, technology and dedication.
Reference Model Definition
Motivation: SysML is a (too) complex language – we need to define which
subset to use and how
Steps:
– Defined Modeling Process
– Defined reference model
• Subset of SysML (elements and diagrams)
• Define metamodel of how model elements are related
• Model organization (views/perspectives)
– Tools customization
• Profile (extension with DSL)
• Diagram Customization
• Validation rules
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WORLD CLASS - through people, technology and dedication.
Reference Model Definition
• Basic Principles
– Avoid redundancy and duplication of information
– Be very clear about the different abstraction levels (hard!)
– Shall not cover all details nor repeat or duplicate information from
other tools (link in instead)
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WORLD CLASS - through people, technology and dedication.
Reference Model Definition
• Process modeled using SysML Activity Diagrams
• Walkthrough (HTML generated from MagicDraw™)
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WORLD CLASS - through people, technology and dedication.
Summary
• MUST make a standardization of modeling to make a maintainable model
– Do systematic stakeholder analysis
– Reference model, guidelines
– Tools customization
• Customized to process and modeling style
• Suite of validation rules
• Build up a core team that is skilled before rolling it out
– Use consultancy
– Do peer modeling
– Both SysML and tools experience required
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WORLD CLASS - through people, technology and dedication.
Summary
• If possible – select a small project (but not too small) and cover all
phases/aspects before rolling it out in large scale
• Do not try to cover all aspects of system engineering/modeling from the
start (eat the elephant piece by piece)
• Be aware on separating between “throw-away” models and maintainable
models
– «less is more»
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WORLD CLASS - through people, technology and dedication.
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