A Practical Guide to SysML

The Systems Modeling Language

Sanford Friedenthal, Alan Moore, Rick Steiner

• Publisher: Morgan Kaufmann
• Year: 2011
• ISBN:
  9780123852076
• Edition: 2
• Topic: Computer Science
• Subtopic: Object Oriented Programming
• Index: Computer Science

A Practical Guide to SysML: The Systems Modeling Language is a comprehensive guide for understanding and applying SysML to model systems. The Object Management Group's OMG SysML is a general-purpose graphical modeling language for representing systems that may include combinations of hardware, software, data, people, facilities, and natural objects. SysML supports the practice of model-based systems engineering (MBSE) used to develop system solutions in response to complex and often technologically challenging problems. The book is organized into four parts. Part I provides an overview of systems engineering, a summary of key MBSE concepts, a chapter on getting started with SysML, and a sample problem highlighting the basic features of SysML. Part II presents a detailed description of the SysML language, while Part III illustrates how SysML can support different model-based methods. Part IV discusses how to transition MBSE with SysML into an organization. This book can serve as an introduction and reference for industry practitioners, and as a text for courses in systems modeling and model-based systems engineering. Because SysML reuses many Unified Modeling Language (UML) concepts, software engineers familiar with UML can use this information as a basis for understanding systems engineering concepts.

• Authoritative and comprehensive guide to understanding and implementing SysML
• A quick reference guide, including language descriptions and practical examples
• Application of model-based methodologies to solve complex system problems
• Guidance on transitioning to model-based systems engineering using SysML
• Preparation guide for OMG Certified Systems Modeling Professional (OCSMP)

Part I

Introduction

Outline

Chapter 1 Systems Engineering Overview

Chapter 2 Model-Based Systems Engineering

Chapter 3 Getting Started with SysML

Chapter 4 An Automobile Example Using the SysML Basic Feature Set

Chapter 1

Systems Engineering Overview

Publisher Summary

This chapter introduces the systems engineering approach independent of modeling concepts to set the context for how SysML is used. Systems engineering is a multidisciplinary approach that is intended to transform a set of stakeholder needs into a balanced system solution that meets those needs. Systems engineering is a key practice to address complex and often technologically challenging problems. The systems engineering process includes activities to establish top-level goals that a system must support, specify system requirements, synthesize alternative system designs, evaluate the alternatives, allocate requirements to the components, integrate the components into the system, and verify that the system requirements are satisfied. It also includes essential planning and control processes needed to manage a technical effort. Multidisciplinary teams are an essential element of systems engineering to address the diverse stakeholder perspectives and technical domains to achieve a balanced system solution. The practice of systems engineering continues to evolve with an emphasis on dealing with systems as part of a larger whole. Systems engineering practices are becoming codified in various standards, which is essential to advancing and institutionalizing the practice across industry domains.

Chapter 1 introduces the systems engineering approach independent of modeling concepts to set the context for how SysML is used. It describes the motivation for systems engineering, introduces the systems engineering process, and then describes a simplified automobile design example to highlight how complexity is addressed by the process. This chapter also summarizes the role of standards, such as SysML, to help codify the practice of systems engineering.

The Object Management Group’s OMG SysML™ [1] is a general-purpose graphical modeling language for representing systems that may include combinations of hardware, software, data, people, facilities, and natural objects. SysML supports the practice of model-based systems engineering (MBSE) that is used to develop system solutions in response to complex and often technologically challenging problems.

This chapter introduces the systems engineering approach independent of modeling concepts to set the context for how SysML is used. It describes the motivation for systems engineering, introduces the systems engineering process, and then describes a simplified automobile design example to highlight how complexity is addressed by the process. This chapter also summarizes the role of standards, such as SysML, to help codify the practice of systems engineering.

The next three chapters in Part I introduce model-based systems engineering, and provide an overview of SysML, and a partial SysML model of the automobile design example introduced in this chapter.

1.1 Motivation for Systems Engineering

Whether it is an advanced military aircraft, a hybrid vehicle, a cell phone, or a distributed information system, today’s systems are expected to perform at levels undreamed of a generation ago. Competitive pressures demand that the systems leverage technological advances to provide continuously increasing capability at reduced costs and within shorter delivery cycles. The increased capability drives requirements for increased functionality, interoperability, performance, reliability, and smaller size.

The interconnectivity among systems also places increased demands on systems. Systems can no longer be treated as stand-alone, but behave as part of a larger whole that includes other systems as well as humans. Systems are expected to support many different uses as part of an interconnected system of systems (SoS). These uses drive evolving requirements that may not have been anticipated when the system was originally developed. An example is how the interconnectivity provided by email and smart phones impacts the requirements on our day-to-day activities. Clearly, email and the use of smart phones can result in unanticipated requirements on us, the users of these technologies, and affect who we communicate with, how often, and how we respond. The same is true for interconnected systems.

The practices to develop systems must support these increasing demands. Systems engineering is an approach that has been dominant in the aerospace and defense industry to provide system solutions to technologically challenging and mission-critical problems. The solutions often include hardware, software, data, people, and facilities. Systems engineering practices have continued to evolve to address the increasing complexity of today’s systems, which is not limited to aerospace and defense systems. As a result, the systems engineering approach has been gaining broader recognition and acceptance across other industries such as automotive, telecommunications, and medical equipment, to name a few.

1.2 The Systems Engineering Process

A system consists of a set of elements that interact with one another, and can be viewed as a whole that interacts with its external environment. Systems engineering is a multidisciplinary approach to develop balanced system solutions in response to diverse stakeholder needs. Systems engineering includes the application of both management and technical processes to achieve this balance and mitigate risks that can impact the success of the project. The systems engineering management process is applied to ensure that development cost, schedule, and technical performance objectives are met. Typical management activities include planning the technical effort, monitoring technical performance, managing risk, and controlling the system technical baseline. The systems engineering technical processes are applied to specify, design, and verify the system to be built. The practice of systems engineering is not static, but continues to evolve to deal with increasing demands.

A simplified view of the systems engineering technical processes is shown in Figure 1.1. The System Specification and Design process is used to specify the system requirements and allocate the component requirements to meet stakeholder needs. The components are then designed, implemented, and tested to ensure that they satisfy their requirements. The System Integration and Test process includes activities to integrate the components into the system and verify that the system requirements are satisfied. These processes are applied iteratively throughout the development of the system, with ongoing feedback between the different processes. In more complex applications, there are multiple levels of system decomposition beginning at an enterprise or SoS level. In those cases, variants of this process are applied recursively to each intermediate level of the design down to the level at which the components are purchased or built.

Figure 1.1 Simplified systems engineering technical processes.

The System Specification and Design process in Figure 1.1 includes the following activities to provide a balanced system solution that addresses the diverse stakeholders’ needs:

Elicit and analyze stakeholder needs to understand the problem to be solved, the goals the system is intended to support, and the effectiveness measures needed to evaluate how well the system supports the goals

Specify the required system functionality, interfaces, physical and performance characteristics, and other quality characteristics to support the goals and effectiveness measures

Synthesize alternative system solutions by partitioning the system design into components that can satisfy the system requirements

Perform trade-off analysis to evaluate and select a preferred solution that satisfies system requirements and provides the optimum balance to achieve the overall effectiveness measures

Maintain traceability from the system goals to the system and component requirements and verification results to ensure that requirements and stakeholder needs are addressed

1.3 Typical Application of the Systems Engineering Process

The System Specification and Design process can be illustrated by applying this process to an automobile design. A multidisciplinary systems engineering team is responsible for executing this process. The participants and roles of a typical systems engineering team are discussed in Section 1.4....

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• Acknowledgments
• About the Authors
• Part I: Introduction
• Part II: Language Description
• Part III: Modeling Examples
• Part IV: Transitioning to Model-Based Systems Engineering
• Appendix A. SysML Reference Guide
• References
• Index