A Practical Guide to SysML

The Systems Modeling Language

Sanford Friedenthal, Alan Moore, Rick Steiner

• Publisher: Morgan Kaufmann
• Year: 2014
• ISBN:
  9780128008003
• Edition: 3
• Topic: Computer Science
• Subtopic: Programming Languages
• Index: Computer Science

A Practical Guide to SysML, Third Edition, fully updated for SysML version 1.4, provides a comprehensive and practical guide for modeling systems with SysML. With their unique perspective as leading contributors to the language, Friedenthal, Moore, and Steiner provide a full description of the language along with a quick reference guide and practical examples to help you use SysML.

The book begins with guidance on the most commonly used features to help you get started quickly. Part 1 explains the benefits of a model-based approach, providing an overview of the language and how to apply SysML to model systems. Part 2 includes a comprehensive description of SysML that provides a detailed understanding that can serve as a foundation for modeling with SysML, and as a reference for practitioners. Part 3 includes methods for applying model-based systems engineering using SysML to specify and design systems, and how these methods can help manage complexity. Part 4 deals with topics related to transitioning MBSE practice into your organization, including integration of the system model with other engineering models, and strategies for adoption of MBSE.

• Learn how and why to deploy MBSE in your organization with an introduction to systems and model-based systems engineering
• Use SysML to describe systems with this general overview and a detailed description of the Systems Modeling Language
• Review practical examples of MBSE methodologies to understand their application to specifying and designing a system
• Includes comprehensive modeling notation tables as an appendix that can be used as a standalone reference

Part I

Introduction

Outline

Introduction

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

Introduction

Part I contains four chapters that provide an overview of systems engineering, a summary of key model-based systems engineering (MBSE) concepts, a chapter on getting started with SysML, and a sample problem to highlight the basic features of SysML. These chapters provide foundations for MBSE with SysML, and prepare the reader for the details of the language in Part II.

Chapter 1

Systems Engineering Overview

Abstract

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.

Keywords

system; system of systems. systems engineering; systems engineering process; systems engineering method; multidisciplinary systems engineering team; systems engineering standard; model and data exchange standards; lifecycle

The Object Management Group’s OMG SysML™ [1] is a general-purpose graphical modeling language for representing systems that may include combinations of hardware and equipment, 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 how this process is applied to a simplified automobile design example. This chapter also summarizes the role of standards, such as SysML, to help codify the practice of systems engineering.

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 unimagined a generation ago. Competitive pressures demand that these systems leverage technological advances to provide continuously increasing capability at reduced costs and within shorter delivery cycles. The increased capability often drives requirements for increased functionality, interoperability, performance, and reliability, often within smaller and smaller devices.

The interconnectivity among systems also places increased demands on systems. Systems can no longer be treated as stand-alone entities. They behave as part of a larger whole that includes other systems, devices, and humans. This interconnected system of systems (SoS) is not static but changes over time as systems are added or removed and as their uses change. These changes result in evolving requirements on constituent systems that may not have been anticipated when the system was developed. An example would be a mobile device that originally provided e-mail communication but evolved to provide Internet functionality, including access to video, global positioning services, and social media. Systems such as automobiles, airplanes, and financial systems are also continuously subject to changing requirements, particularly as they become more interconnected.

Systems engineering is an approach that has been widely accepted in the aerospace and defense industry to provide system solutions to technologically challenging and mission-critical problems. The solutions often include hardware and equipment, software, data, people, and facilities. The potential value that systems engineering offers for managing complexity and risk and improving productivity and quality has been gaining 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 to achieve an objective. Systems engineering is a multidisciplinary approach to develop balanced system solutions in response to diverse stakeholder needs. Systems engineering includes both management and technical processes to achieve this balance and mitigate risks that can affect the success of the project. The systems engineering management process is intended 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 used to analyze, specify, design, and verify the system to ensure the pieces work together to achieve the objectives of the whole. The practice of systems engineering is not static but evolves to deal with the increasing demands mentioned previously.

A simplified view of the systems engineering technical process is shown in Figure 1.1. The System Specification and Design process is used to specify system requirements that will meet the needs of the stakeholders. It then allocates the requirements to the components of the system. The components are designed, implemented, and tested to ensure they satisfy the requirements. The System Integration and Test process includes activities to integrate the components into the system and verify that the system satisfies its requirements. These processes are applied iteratively throughout the development of the system, with ongoing feedback from the different processes. In more complex applications, multiple levels of system decomposition begin at an enterprise or system of systems 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 procured or built.

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 these goals and satisfies the stakeholder needs.

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

FIGURE 1.1 Simplified systems engineering technical processes.

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

• Perform analysis to evaluate and select a preferred system solution that satisfies the system requirements and maximizes the 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 described in Section 1.2 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.

The team must first identify the stakeholders and analyze their needs. Stakeholders include the purchaser of the car and the users of the car, whic...