John M. Borky

Implementing Governance to Measure and Maintain Architecture Quality

We have reserved for this final chapter a discussion of the overarching theme of measuring and preserving the technical quality and integrity of an architecture. We discussed the related topic of architecture validation in Chap. 11. Architecture governance is both vitally necessary and frequently neglected. Systems and enterprises live in a dynamic environment of constant changes in technologies, business goals and processes, user needs, and hostile threats. As a result, an architecture that is initially open, resilient, operationally effective, and affordable may degrade over time unless positive controls are in place to guide decision-making. We begin by discussing the basics of preserving architecture quality and introduce quantitative quality measures. Our goal is to counter the common but erroneous belief that architecture is inherently immeasurable and thus that governance is impractical. We employ Quality Attributes (QAt) as the basic mechanism for achieving this, making architecture governance both feasible and essential. We describe the essential elements of a governance organization and process, and we provide enough examples of effective QAts to guide a system architecture team in devising a sound governance strategy. The key point is that the application of a methodology like MBSAP will ultimately be in vain if it is not accompanied by a long-term commitment to architecture governance. The chapter objective is the reader will be able to define and implement a process for assessment and governance that supports high architecture quality over a system’s lifetime.

Implementing Service-Oriented Architectures for Enterprise Integration

We have introduced the idea of Service-Oriented Architecture (SOA) a number of times in earlier chapters, and we now explore the subject in a more focused and specific way. SOA, in general, and its latest incarnation in cloud computing have become dominant factors in contemporary information technology. Our primary objective is to give system architects and engineers a sufficient grounding in SOA principles and practices to allow them to effectively incorporate services in systems and enterprises and a starting point for more in-depth study of this complex and rapidly evolving technology. First, we present the fundamental concepts of services and a service-oriented style of architecture. We then lay out the essential foundation of SOA concepts and the building blocks with which a SOA is erected. SOA projects have been reported to have failed due to faulty strategy and planning, and we discuss important aspects of preparing and executing service-enabled solutions. We consider practical aspects of SOA implementation. Recognizing that SOA is intimately related to the constantly changing World Wide Web, we briefly summarize in Sect. 7.5 the trends and expected future evolution of the Web. This is followed by a summary of the current Web Services Framework. Finally, we return to MBSAP and present specific techniques for service modeling, using the Smart Microgrid system example that gives an illustration. Chapter objective: the reader will be able to apply the MBSAP methodology to the definition, planning, modeling, and implementation of service-enabled systems and enterprises, including SOA structures and elements and the most important service standards and specifications.

Protecting Information with Cybersecurity

Virtually every system today confronts the cybersecurity threat, and the system architect must have the ability to integrate security features and functions as integral elements of a system. In this chapter, we survey this large, complex, and rapidly evolving subject with the goal of giving the reader a level of understanding that will enable incorporation of cybersecurity within an MBSE process and effective interaction with security experts. We begin by introducing the subject and describing the primary aspects of the current cybersecurity environment. We define fundamental terminology and concepts used in the cybersecurity community, and we describe the basic steps to include cybersecurity risk in an overall risk management process, which is a central SE responsibility. We then list some of the primary sources of information, guidance, and standards upon which a systems engineer can and should draw. Next, we summarize the major aspects of incorporating security controls in a system architecture and design to achieve an acceptable level of security risk for a system. We extend this to the increasingly important world of service-oriented, network-based, and distributed systems. We conclude with a brief presentation of the application of MBSAP to the specific issues of cybersecurity and summarize the characteristics of a Secure Software Development Life Cycle aimed at creating software with minimum flaws and vulnerabilities. We illustrate the application of cybersecurity principles and practices using the Smart Microgrid example. Chapter Objective: the reader will be able to apply the MBSAP methodology to systems and enterprises that require protection of sensitive data and processes against the growing cybersecurity threat and to work effectively with cybersecurity specialists to achieve effective secure system solutions.

Analyzing Requirements in an Operational Viewpoint

This is the first of three chapters spelling out the MBSAP methodology in detail. The Operational Viewpoint (OV) transforms a customer’s requirements, which may be documented in a Capabilities or Requirements Database, into an architectural context by mapping them into a high-level definition of system structure, behavior, information content, services, and other content. We address the creation of a system requirements baseline, including the important distinction between function and nonfunctional requirements. We describe the successive activities involved in creating the model while recognizing that the process is inherently both parallel and interactive in treating the various Perspectives of the OV. We present the two system examples that are used throughout the book, the E-X Airborne sensor Platform and a family of Smart Microgrids. We then define a set of architecture styles that may shed light on the fundamentals of architecture for a system category. We apply the diagrams and techniques from Chap. 2, especially Block, Use Case, and Activity Diagrams, and introduce the use of model element specifications to fully define the architecture. We discuss in detail the process of creating the Perspectives of the OV. We show briefly the equivalent content of an OV for the very different case of the Smart Microgrid. We conclude the chapter with a short discussion of executable architecture, which will be developed in more detail in later chapters. The chapter objective is the reader will be able to create an OV in a SysML model using the sequence of activities in the MBSAP methodology to create a requirements baseline and transform it into a high-level architecture.

Designing in a Logical/Functional Viewpoint

This chapter describes the next phase of the MBSAP process, showing how the top-level architecture from the Operational Viewpoint (OV) is transformed into a functional design of the system in a Logical/Functional Viewpoint (LV). We familiarize the reader with the concepts and techniques involved in carrying the five Perspectives of the OV to the level of a functional architecture, using the E-X example for illustration. We discuss design patterns, making the point that although these arose in the world of software, they have great applicability and payoff when applied to entire systems. For example, we show how Domains are decomposed to the level of actual system components, modeled as Blocks. Similarly, we will take the representation of system behaviors down to individual Blocks or groups of Blocks and begin to look at the timing of system functions. In the Data Perspective, we illustrate the use of Inheritance to specialize Foundation Classes from the Conceptual Data Model into actual system data entities in a Logical Data Model. We introduce the key subject of layered architectures that are organized on the basis of services to create a computing platform on which applications software and user interfaces can be hosted. Next, we show what the LV looks like in the Smart Microgrid. When the LV is complete and fully documented, the system architect can furnish a set of functional specifications and other architecture artifacts to hardware and software developers, procurement and material management specialists, and others to use in implementing, integrating, testing, producing, and sustaining the system. We end the chapter with a discussion of executable architectures and a summary of key points in the LV. Chapter objective: the reader will be able to transform the high-level architecture of an OV into a functional design in an LV with supporting implementation documentation.

Using Prototypes, Verification, and Validation to Evaluate and Enhance System Architecture

The MBSAP methodology is tied together by a prototyping environment that allows an evolving system architecture to be exercised and assessed for purposes as diverse as verification and validation (V&V), performance analysis, trade study quantification, and human-in-the-loop experimentation. It has two complementary dimensions: a physical prototype is built up from real or emulated system components, while a virtual prototype brings together a set of system simulations. The virtual prototyping strategy mirrors the levels of the Axis of Abstraction of the architecture taxonomy in Chap. 1. First, we establish the fundamental concepts and terminology and explore the details of physical and virtual prototypes. We then present the essentials of V&V and the role of prototyping and simulation, and we discuss additional uses of prototyping to support a system development effort. We briefly summarize an alternative approach to SysML using Petri nets. Finally, we use the Smart Microgrid and E-X examples to illustrate these prototyping concepts. The essential idea is that a properly planned and executed prototyping activity can be of great value in reducing risk, saving cost and schedule, enhancing system V&V, and supporting many other aspects of the system life cycle. Chapter Objective: the reader will be able to define an effective prototyping strategy, including virtual and physical prototypes, and to incorporate prototypes in the planning, execution, and assessment of a system development program.

Developing the Network Dimension

Since so many high-technology systems and enterprises are networked, and since network vulnerabilities are involved in so many cyberattacks, we provide in this chapter a concise summary of networking basics. We present the primary categories of networks and networking devices, along with the standard models used to describe them. We summarize both the seven-layer Open Systems Interconnect (OSI) model and the simpler and more current four-layer Internet protocol model. We discuss some practical aspects of networking media and devices. The remainder of the chapter introduces important variations on a basic networking scheme, including wireless, virtual, and mobile networks. The sheer number of protocols and standards can be overwhelming, and in the chapter itself as well as in Appendix J, we tabulate the more significant of these and spell out many of the associated acronyms. As with other specialized architecture topics, our goal is to equip the system architect with sufficient background to deal with this aspect of a system and to work effectively with experts in the field. Chapter Objective: the reader will have a level of familiarity with networks and networking components that allows effective design, modeling, and analysis of this crucial area of system and enterprise architectures.

Applying Advanced Concepts

In this short chapter, we collect a set of topics that may be significant in specific architecting situations but lie outside the main flow of material in the book. Most of these are relatively recent developments, and all of them are experiencing growing levels of interest and use in Systems Engineering and Architecture. We summarize Virtualization, which deals with a number of schemes for emulating or abstracting computing resources to create virtual versions that are more efficient and flexible than the actual hardware and software in a wide range of computing environments. We discuss a related topic, Clustering, which is a particular kind of hardware virtualization that integrates a set of resources, usually servers, to create a single platform. Next, we consider several varieties of Distributed Computing, which share the goal of coordinating and employing dispersed resources to create powerful and resilient computing capability. One version of this is a primary constituent of cloud computing, which is perhaps the most prominent current trend in information technology and which, itself, has multiple variants. We look briefly at agents and proxies and summarize several advanced algorithms, including artificial neural networks and genetic algorithms. Finally, we touch on several important aspects of the mechanical design of systems. Chapter Objective: the reader will acquire a basic understanding of important technologies that impact contemporary system architecture.

Introduction: Framing the Problem

In this opening chapter, we establish the background of Model-Based Systems Engineering (MBSE) in terms of the evolution of complex, high-technology systems and the challenges those systems present. This material is the essential foundation for the remainder of the book. We open the discussion by considering the aesthetic and technical dimensions of system architecting and provide the underlying rationale for MBSE. We then describe the historical context for our subject and start a process of defining terms that will continue in the following chapters. Because the subject of open architecture is so fundamental in contemporary systems engineering, we devote a discussion to its basic principles. Most importantly for the remainder of the book, we then define a taxonomy and accompanying set of terms that will allow us to place various system architectures in consistent categories , avoiding misunderstandings and allowing us to discover characteristics that are shared among systems of a given kind. We also introduce a set of fundamental tenets of good system architecture, which will be used throughout the book. Finally, we briefly consider how architecture can contribute to successful system developments and the roles it should play in a program plan. Chapter objective: the reader will be able to describe and plan the role of MBSE in a complex system development, including the importance of achieving the tenets of effective architecture.

Applying Object Orientation to System Architecture

In this chapter, we provide the essential theory and practical details of employing the principles of Object Orientation (OO) in system architecture modeling. We do not attempt to provide an exhaustive OO tutorial, since there exists a very large literature on this subject (see the references to this chapter). Our goal, instead, is to give the reader the level of understanding needed to master the MBSAP methodology and apply it to practical system architecting challenges. First, we present the rationale for OO and define the essential concepts and terminology, stressing the benefits it delivers in dealing with complex entities. Although we use the Systems Modeling Language (SysML) as the basis for this book, we begin by discussing and illustrating the primary diagrams of the Unified Modeling Language (UML), which is the root language standard for OO. This is then followed by a description of the changes to UML introduced by the SysML, which is defined as a Profile of UML. The reality is that a large part of the SysML is taken directly from the UML language specification. We believe understanding of this material is enhanced by first considering the parent UML and then explicitly showing how UML modifies and extends the language. We include generic UML and SysML diagrams that illustrate important principles and syntax and that can serve as format samples in developing real architecture models. Appendices A and B are concise references to UML and SysML, respectively, intended to give readers a quick and easy way to look up the details. Chapter objective: the reader will be able to create and read UML and SysML diagrams and to describe the role of each.