SysML Reference Model DefinitionModel 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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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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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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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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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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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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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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Reference Model Definition

• Process modeled using SysML Activity Diagrams

• Walkthrough (HTML generated from MagicDraw™)

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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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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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