ISBN-10:
0201498375
ISBN-13:
9780201498370
Pub. Date:
05/07/1999
Publisher:
Addison-Wesley
Doing Hard Time: Developing Real-Time Systems with UML, Objects, Frameworks and Patterns / Edition 1

Doing Hard Time: Developing Real-Time Systems with UML, Objects, Frameworks and Patterns / Edition 1

by Bruce Powel Douglass
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Product Details

ISBN-13: 9780201498370
Publisher: Addison-Wesley
Publication date: 05/07/1999
Series: Addison-Wesley Object Technology Series
Edition description: New Edition
Pages: 688
Product dimensions: 7.64(w) x 9.54(h) x 1.66(d)

About the Author

Bruce Powel Douglass is the Chief Evangelist for i-Logix, a leading producer of tools for real-time systems development. He contributed to the original specification of the UML and to the UML 2.0 as one of the co-chairs of the Object Management Group’s Real-Time Analysis and Design Working Group. Bruce consults for a number of companies and organizations, including NASA, on building large-scale, real-time, safety-critical systems. He is the author of seven other books, including Real-Time Design Patterns (Addison-Wesley, 2003) and Doing Hard Time (Addison-Wesley, 1999).

Read an Excerpt

Goals

Today's world literally runs on embedded computers. Virtually every field of endeavor in our modern society depends on embedded computers from manufacturing to transportation to medicine. The typical household is a computing eco-system that includes telephones, televisions, washing machines, ovens, and a host of other silicon-based fauna. Many, if not most, of these computing devices have timeliness requirements to their functionality, so that late action is often wrong action. Many embedded devices have the capacity to do great harm if they malfunction or fail.

Not only are more things being handled by embedded computing devices, but the scope, complexity, and criticality of the things being handled is increasing geometrically. Technological advances are crucial in order to keep up with the increasing demands on the developer of such systems. Gone are the days when the hardware complexity was the limiting factor in the development of electrical devices. Most companies involved in the manufacture of real-time and embedded systems have realized the truism of "the tail that wags the dog" and have begun seriously looking at ways to improve software productivity. These better ways to develop real-time and embedded systems are the source and soul of this book.

Doing Hard Time: Designing and Implementing Embedded Systems with UML focuses on model-based development of real-time and embedded systems using the Unified Modified Language (UML) and a risk-based iterative development lifecycle called ROPES. UML is a 3rd generation modeling language that rigorously defines the semantics of the object metamodel and provided a notation for capturing andcommunicating object structure and behavior. The UML became a standard modeling language in the OMG in late 1996, and the author remains heavily involved in its ongoing effort. This book is based upon the 1.3 revision of the UML standard.

Model-based development is crucial in today's high-complexity, short-development-cycle business environment. It is important to focus on the fundamental abstractions of the problem rather than on the low-level details of its implementation; to focus on "should the control rods be in the reactor core to avoid a meltdown?" rather than "should I jump on non-zero or carry?" By increasing the level of abstraction, it is possible to build more complex systems with fewer defects in less time—a winning combination for everyone concerned.

Because the UML is executable, it is possible to automatically generate executable systems from UML models. The importance of this goes well beyond simply saving the time and effort of hand-translating code from abstract models. It is an enabling technology, allowing the developer to rapidly move from the inception of a concept to the testing of that concept. This allows early risk reduction and encourages exploration of the solution space. Conceptual defects can be identified and fixed very early before many dependencies on the flawed concepts are created, resulting in higher-quality systems in less calendar time.

This book is meant to be a fusion of a number of subject domains almost universally left disjoint—real-time concepts such as timeliness and performance, object modeling, a rapid development process, and system safety. This unified approach allows the developer to follow simple and well-understood process steps culminating with the delivery of correct and timely embedded solutions.

There are very few books on using objects in real-time systems and even fewer that use the latest in object modeling languages—the UML. Virtually all object-oriented books focus primarily on business or data base application domains and do not mention real-time aspects at all. On the other hand, texts on real-time systems have largely ignored object-oriented methods. For the most part, such books fall into two primary camps: those that bypass methodological considerations altogether and focus solely on "bare metal" programming and those that are highly theoretical with little advice for actually implementing workable systems. Doing Hard Time is meant to bridge for these technologies, presenting the development of deployable real-time systems using the object semantics and notation of the UML. It does so in a tool-independent manner, even though it does use a particular tool to demonstrate the examples. Audience

The book is oriented towards the practicing professional software developer and the computer science major, in the junior year or higher. The book could serve as an undergraduate or graduate level text, but the focus is on practical development rather than a theoretical introduction. A few equations are to be found in this book, but more theoretical and mathematical approaches are referenced where appropriate. The book assumes a reasonable proficiency in at least one programming language and at least a cursory exposure to the fundamental concepts of both object orientation and real-time systems. Organization

This book is organized into 5 sections:

  • The Basics
This section introduces the object semantics and notation of the UML, real-time systems, safety criticality, and development processes.
  • Analysis
This section deals with the various kinds of analysis, including the capturing of requirements with use cases, scenarios, and state machines, the identification of the key abstractions in a problem, and modeling the fundamental behavior.
  • Design
This section focuses on the addition of design level information, such as the concurrency model, creation of run-time artifacts (libraries, executables, and so on), mapping to physical architectures, the application of design patterns to optimize collaborations of objects, and modeling of algorithms.
  • Advanced Real-Time Modeling
This section discusses topics of interest in difficult or complex real-time and embedded applications. These topics include the determination of the schedulability of object models through mathematical analysis, the reification of general state machine solutions to commonly occurring behavioral problems into behavioral design patterns, and the structure and function of real-time frameworks.
  • Appendices
This book provides three appendices:
  1. UML Notational Guide: A short guide to the notations used in the UML and in the book.
  2. Introduction to Rhapsody: An introduction to the UML visual programming tool provided in the accompanying CD-ROM.
  3. Introduction to TimeWiz: An introduction to the schedulability analysis tool provided in the accompanying CD-ROM.
CD-ROM

The CD-ROM provided with this book contains three kinds of things:

  • The examples presented within the pages of the book
These models are given as Rhapsody projects and can be opened and manipulated with Rhapsody.
  • Rhapsody
The visual programming tool installation files.
  • TimeWiz
The schedulability analysis tool installation files.

I believe (and hope) that the needs of both the student and professional developer will be addressed by this book, and it is in this spirit that I offer it. Acknowledgments

I wish to express thanks to my reviewers who tried hard to keep me honest and on topic, and who, I think, more or less succeeded:

Eran Gery, i-Logix
Jim Collins, i-Logix
Larry McAlister, ENSCO, Inc.
Therese M. Douglass, Air Traffic Software Architecture, Inc.
Gary Cernosek, Rational Software Corp.

I would also like to thank Neeraj Chandra and Gene Robinson of i-Logix for their support in allowing me to spend so much effort on this book, Doug Jensen of Mitre for his input on schedulability, Therese Douglass for her expertise in air traffic control systems, and the editorial team at Addison-Wesley, including Carter Shanklin, Krysia Bebick, and Maureen Willard, to name a few. Bruce Powel Douglass, Ph.D.
Deep, Dark Winter, (early) 1999

Table of Contents

(Chapters begin with an Introduction and conclude with a Summary, Looking Ahead, Exercises and References.)

Figure List.

About the Author.

Preface.

Acknowledgments.

SECTION 1: BASICS.

1. Introduction to Objects and the Unified Modeling Language.

Advantages of Objects.

Terms and Concepts.

Object Orientation with UML.

Objects.

Attributes.

Behavior.

Messaging.

Responsibility.

Concurrency.

Objects as Autonomous Machines.

Class Diagrams.

Relations Among Classes and Objects.

Use Cases.

Sequence Diagrams.

Physical Representation.

Things Common to Diagrams.

Notes.

Packages.

Constraints.

Stereotypes.

2. Basic Concepts of Real-Time Systems.

What is Real-Time?

Terms and Concepts.

Timeliness.

Responsiveness.

Concurrency.

Scheduling Concurrent Threads.

Event Arrival Patterns.

Thread Rendezvous Patterns.

Sharing Resources.

Predictability.

Memory Management.

Correctness and Robustness.

Deadlock.

Exceptional Conditions.

Race Conditions.

Distributed Systems.

Fault Tolerance and Safety.

Dealing with Resource-Limited Target Environments.

Low-Level Hardware Interfacing.

Real-Time Operating Systems.

Scalability.

Scheduling.

Typical RTOS Features.

3. Basic Concepts of Safety-Critical Systems.

Introduction to Safety.

The Therac-25 Story.

Other Stories.

Terms and Concepts.

Safety Related Faults.

Safety is a System Issue.

Random Faults Versus Systematic Faults.

Single Point Failures.

Common Mode Failures.

Latent Faults.

Fail-Safe State.

Achieving Safety.

Safety Architectures.

Single Channel Protected Design.

Eight Steps to Safety.

Step 1: Identify the Hazards.

Step 2: Determine the Risks.

Step 3: Define the Safety Measures.

Step 4: Create Safe Requirements.

Step 5: Create Safe Design.

Step 6: Implementing Safely.

Step 7: Assure Safety Process.

Step 8: Test, Test, Test.

Few Safety Related Standards.

4. Rapid Object-Oriented Process for Embedded Systems.

Terms and Concepts.

Development Phases.

Ordering.

Maturity.

Development Task Sequencing.

Waterfall Lifecycle.

Iterative Lifecycles.

Prototyping.

Scheduling and Estimation.

Advantages of Accurate Schedules.

Difficulties of Accurate Scheduling.

The ROPES Macro Cycle.

Analysis.

Requirements Analysis.

Systems Analysis.

Object Analysis.

Design.

Architectural Design.

Mechanistic Design.

Detailed Design.

Translation.

Activities.

Artifacts.

Testing.

Activities.

SECTION 2: ANALYSIS.

5. Requirements Analysis of Real-Time Systems.

Terms and Concepts.

Use Cases.

Messages and Events.

Scenarios, Protocols, and State Machines.

Use Cases.

Use Case Relations.

Use Case Example: Air Traffic Control System.

External Events.

Context-Level Messages.

Specifying External Messages.

External Event List.

Response Time.

Detailing Use Case Behavior.

Informal Textual Description.

Scenarios.

Sequence Diagrams.

Statecharts for Defining Use Case Behavior.

Identifying Use Cases.

Using Use Cases.

Heuristics for Good Requirements Analysis Diagrams.

Use Case Diagram Heuristics.

Use Case Heuristics.

Use Case Sequence Diagram Heuristics.

6. Structural Object Analysis.

Terms and Concepts.

Key Strategies for Object Identification.

Underline the Noun.

Identify Causal Agents.

Identify Coherent Services.

Identify Real-World Items.

Identify Physical Devices.

Identify Essential Abstractions of Domains.

Identify Transactions.

Identify Persistent Information.

Identify Visual Elements.

Identify Control Elements.

Execute Scenarios on the Object Model.

Reification of Objects into Classes.

Identify Object Associations.

Multiplicity.

Associations and Links.

Aggregation and Composition.

Object Attributes.

Generalization Relationships.

AATCS Example: Class Diagrams.

Heuristics for Good Class Diagrams.

Rules for Good Class Diagrams.

7. Object Behavioral Analysis.

Terms and Concepts.

Simple Behavior.

State Behavior.

Continuous Behavior.

UML Statecharts.

Basic State Semantics.

Transitions and Events.

Actions and Activities.

Pseudostates.

Orthogonal Regions and Synchronization.

Basic Statechart Syntax.

Inherited State Models.

Ill-formed State Models.

Example: AATCS Alarm System.

The Role of Scenarios in the Definition of Behavior.

Timing Diagrams.

Sequence Diagrams.

Activity Diagrams.

Defining Operations.

Types of Operations.

Strategies for Defining Operations.

Statechart Heuristics.

Timing Diagram Heuristics.

Activity Diagram Heuristics.

SECTION 3: DESIGN.

8. Architectural Design.

Terms and Concepts.

Tasking Model.

Representing Tasks.

Defining Task Threads.

Assigning Objects to Tasks.

Defining Task Rendezvous.

Component Model.

Deployment Model.

Representing Physical Architecture in the UML.

Multiprocessor Systems.

Safety/Reliability Model.

9. Mechanistic Design.

Terms and Concepts.

Design Pattern Basics.

Mechanistic Design Patterns.

Correctness Patterns.

Execution Control Patterns.

10. Detailed Design.

Introduction to Detailed Design.

Terms and Concepts.

Data Structure.

Primitive Representational Types.

Subrange Constraints.

Derived Attributes.

Data Collection Structure.

Associations.

The Object Interface.

Definition of Operations.

Detailed Algorithmic Design.

Representing Algorithms in the UML.

Algorithmic Example: Run-Time Data Interpolation.

Exceptions.

Source Language-based Exception Handling.

State-based Exception Handling.

SECTION 4. ADVANCED REAL-TIME MODELING.

11. Threads and Schedulability.

Terms and Concepts.

Time-Based Systems.

Reactive Systems.

Time Concepts.

Scheduling Threads.

Rate Monotonic Scheduling.

Earliest Deadline Scheduling.

Least Laxity Dynamic Scheduling.

Maximum Urgency First Scheduling.

Weighted Shortest Processing Time First (WSPTF) Scheduling.

Minimizing Maximum Lateness Scheduling.

Thread Synchronization and Resource Sharing.

Mutual Exclusion Semaphore.

Dekker's Algorithm.

Spinlocks.

Counting Semaphores.

Condition Variables.

Barriers.

Rendezvous Objects.

Schedulability Analysis of Hard Real-Time Systems.

Global Analysis.

Global Method with Blocking.

Computing Blocking.

Separate Task Utilization Bounds.

Aperiodic Tasks.

Schedulability Analysis of Soft Real-Time Systems.

Warm and Fuzzy: Timeliness in the Soft Context.

Soft Schedulability.

12. Dynamic Modeling.

Terms and Concepts.

But is it the Right State Machine?

Behavioral Patterns.

Latch State Pattern.

Polling State Pattern.

Latched Data Pattern.

Device Mode State Pattern.

Transaction State Pattern.

Component Synchronization State Pattern.

Barrier State Pattern.

Event Hierarchy State Pattern.

Random State Pattern.

Null State Pattern.

Watchdog State Pattern.

Retriggerable Counter State Pattern.

Model-Level Debugging and Testing.

Animated Debugging.

Animated Testing.

Sample Debugging Session.

13. Real-Time Frameworks.

Terms and Concepts.

Real-Time Frameworks.

Architectural Support Patterns.

Safety and Reliability Patterns.

Behavioral Patterns.

Framework Design Principles and Metrics.

Set of Services.

Generalization Hierarchy Structure.

Replaceable Components.

Portability.

Naming and Syntax Conventions.

Performance.

The Rhapsody Object Execution Framework (OXF).

Rhapsody Architecture.

Execution Framework.

Interobject Association Patterns.

Using C++ Standard Template Library.

Abstract Operating System.

Animation Framework.

Sample Application Using the Rhapsody OXF Framework.

Appendix A: UML Notation Summary.

Appendix B: Introduction to Rhapsody.

Appendix C: Introduction to Timewiz.

Index.

CD-ROM Warranty.

Preface

Goals

Today's world literally runs on embedded computers. Virtually every field of endeavor in our modern society depends on embedded computers from manufacturing to transportation to medicine. The typical household is a computing eco-system that includes telephones, televisions, washing machines, ovens, and a host of other silicon-based fauna. Many, if not most, of these computing devices have timeliness requirements to their functionality, so that late action is often wrong action. Many embedded devices have the capacity to do great harm if they malfunction or fail.

Not only are more things being handled by embedded computing devices, but the scope, complexity, and criticality of the things being handled is increasing geometrically. Technological advances are crucial in order to keep up with the increasing demands on the developer of such systems. Gone are the days when the hardware complexity was the limiting factor in the development of electrical devices. Most companies involved in the manufacture of real-time and embedded systems have realized the truism of "the tail that wags the dog" and have begun seriously looking at ways to improve software productivity. These better ways to develop real-time and embedded systems are the source and soul of this book.

Doing Hard Time: Designing and Implementing Embedded Systems with UML focuses on model-based development of real-time and embedded systems using the Unified Modified Language (UML) and a risk-based iterative development lifecycle called ROPES. UML is a 3rd generation modeling language that rigorously defines the semantics of the object metamodel and provided a notation for capturing and communicating object structure and behavior. The UML became a standard modeling language in the OMG in late 1996, and the author remains heavily involved in its ongoing effort. This book is based upon the 1.3 revision of the UML standard.

Model-based development is crucial in today's high-complexity, short-development-cycle business environment. It is important to focus on the fundamental abstractions of the problem rather than on the low-level details of its implementation; to focus on "should the control rods be in the reactor core to avoid a meltdown?" rather than "should I jump on non-zero or carry?" By increasing the level of abstraction, it is possible to build more complex systems with fewer defects in less time--a winning combination for everyone concerned.

Because the UML is executable, it is possible to automatically generate executable systems from UML models. The importance of this goes well beyond simply saving the time and effort of hand-translating code from abstract models. It is an enabling technology, allowing the developer to rapidly move from the inception of a concept to the testing of that concept. This allows early risk reduction and encourages exploration of the solution space. Conceptual defects can be identified and fixed very early before many dependencies on the flawed concepts are created, resulting in higher-quality systems in less calendar time.

This book is meant to be a fusion of a number of subject domains almost universally left disjoint--real-time concepts such as timeliness and performance, object modeling, a rapid development process, and system safety. This unified approach allows the developer to follow simple and well-understood process steps culminating with the delivery of correct and timely embedded solutions.

There are very few books on using objects in real-time systems and even fewer that use the latest in object modeling languages--the UML. Virtually all object-oriented books focus primarily on business or data base application domains and do not mention real-time aspects at all. On the other hand, texts on real-time systems have largely ignored object-oriented methods. For the most part, such books fall into two primary camps: those that bypass methodological considerations altogether and focus solely on "bare metal" programming and those that are highly theoretical with little advice for actually implementing workable systems. Doing Hard Time is meant to bridge for these technologies, presenting the development of deployable real-time systems using the object semantics and notation of the UML. It does so in a tool-independent manner, even though it does use a particular tool to demonstrate the examples.

Audience

The book is oriented towards the practicing professional software developer and the computer science major, in the junior year or higher. The book could serve as an undergraduate or graduate level text, but the focus is on practical development rather than a theoretical introduction. A few equations are to be found in this book, but more theoretical and mathematical approaches are referenced where appropriate. The book assumes a reasonable proficiency in at least one programming language and at least a cursory exposure to the fundamental concepts of both object orientation and real-time systems.

Organization

This book is organized into 5 sections:

  • The Basics
This section introduces the object semantics and notation of the UML, real-time systems, safety criticality, and development processes.
  • Analysis
This section deals with the various kinds of analysis, including the capturing of requirements with use cases, scenarios, and state machines, the identification of the key abstractions in a problem, and modeling the fundamental behavior.
  • Design
This section focuses on the addition of design level information, such as the concurrency model, creation of run-time artifacts (libraries, executables, and so on), mapping to physical architectures, the application of design patterns to optimize collaborations of objects, and modeling of algorithms.
  • Advanced Real-Time Modeling
This section discusses topics of interest in difficult or complex real-time and embedded applications. These topics include the determination of the schedulability of object models through mathematical analysis, the reification of general state machine solutions to commonly occurring behavioral problems into behavioral design patterns, and the structure and function of real-time frameworks.
  • Appendices
This book provides three appendices:
  1. UML Notational Guide: A short guide to the notations used in the UML and in the book.
  2. Introduction to Rhapsody: An introduction to the UML visual programming tool provided in the accompanying CD-ROM.
  3. Introduction to TimeWiz: An introduction to the schedulability analysis tool provided in the accompanying CD-ROM.

CD-ROM

The CD-ROM provided with this book contains three kinds of things:

  • The examples presented within the pages of the book
These models are given as Rhapsody projects and can be opened and manipulated with Rhapsody.
  • Rhapsody
The visual programming tool installation files.
  • TimeWiz
The schedulability analysis tool installation files.

I believe (and hope) that the needs of both the student and professional developer will be addressed by this book, and it is in this spirit that I offer it.

Acknowledgments

I wish to express thanks to my reviewers who tried hard to keep me honest and on topic, and who, I think, more or less succeeded:

Eran Gery, i-Logix
Jim Collins, i-Logix
Larry McAlister, ENSCO, Inc.
Therese M. Douglass, Air Traffic Software Architecture, Inc.
Gary Cernosek, Rational Software Corp.

I would also like to thank Neeraj Chandra and Gene Robinson of i-Logix for their support in allowing me to spend so much effort on this book, Doug Jensen of Mitre for his input on schedulability, Therese Douglass for her expertise in air traffic control systems, and the editorial team at Addison-Wesley, including Carter Shanklin, Krysia Bebick, and Maureen Willard, to name a few.

Bruce Powel Douglass, Ph.D.
Deep, Dark Winter, (early) 1999

0201498375P04062001

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