TLA+规格说明：硬件与软件工程师的语言与工具

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"Specifying Systems" 是一本关于TLA+语言和工具的书籍，由Leslie Lamport撰写，面向硬件和软件工程师，介绍如何规范系统设计。本书详细阐述了规格说明的重要性和方法，特别是通过使用TLA+（Temporal Logic of Actions，行为时态逻辑）这一形式化方法。TLA+是一种强大的工具，它允许工程师精确地定义和验证复杂系统的行为，无论是硬件设计还是软件系统。此书的第一版出版于2002年6月18日，由Microsoft Research出版，其内容遍布全球多个城市。书中内容可能涵盖了以下几个关键知识点： 1. **TLA+语言基础**：TLA+由一系列符号和语法组成，用于描述系统的状态和转换。它包括动作、过程、算法和时序逻辑等概念，使得系统的行为可以用数学语言精确表述。 2. **形式化规格说明**：书中详细介绍了如何使用TLA+来编写形式化规格，这些规格能捕捉系统的正确性和所需行为，从而帮助在设计阶段发现潜在问题。 3. **PlusCal算法语言**：PlusCal是TLA+的一个扩展，它提供了一种更接近程序语言的语法，用于描述计算过程。工程师可以使用PlusCal来建模并发和分布式系统，然后自动翻译成TLA+规格。 4. **模型检查**：书中可能涵盖了使用TLA+ Toolbox进行模型检查的方法。模型检查是一种自动化技术，可以验证规格是否满足特定的性质，例如无死锁或无错误状态。 5. **错误检测与修复**：通过学习这本书，读者可以学会如何识别规格中的错误，并使用TLA+工具集来修复这些问题，确保设计符合预期。 6. **案例研究**：书中可能包含实际的硬件和软件工程案例，通过这些案例，读者可以更好地理解如何将TLA+应用到实际项目中，解决复杂设计问题。 7. **工程实践**：作者Leslie Lamport是并发理论和形式化方法的知名专家，他可能会分享他在系统规范方面的经验和最佳实践，指导读者如何有效地将TLA+融入工程流程。 8. **知识产权声明**：书中的法律声明提示读者注意商标和版权问题，强调出版者和作者虽然尽力确保信息的准确性，但不承担因使用书中信息导致的任何直接或间接损害的责任。 "Specifying Systems" 提供了一个全面的指南，帮助工程师们理解和应用TLA+来提高系统设计的质量和可靠性。通过学习此书，读者可以提升其在规格说明、验证和模型检查方面的技能，从而在工程实践中避免或减少潜在的错误和缺陷。

xvi

LIST OF FIGURES AND TABLES

11.7 Mo dule

InnerSequential

. . . . . . . . . . . . . . . . . . . . . . . 201

14.1 The alternating bit proto col . . . . . . . . . . . . . . . . . . . . . 223

14.2 Mo dule

MCAlternatingBit

. . . . . . . . . . . . . . . . . . . . . . 227

14.3 A conguration le for mo dule

MCAlternatingBit

. . . . . . . . . 227

14.4 A sp ecication of correctness of the alternating bit proto col. . . . 229

14.5 The standard mo dule

TLC

. . . . . . . . . . . . . . . . . . . . . . 248

14.6 The BNF grammar of the conguration le. . . . . . . . . . . . . 263

18.1 The standard

Sequences

module. . . . . . . . . . . . . . . . . . . 341

18.2 The standard

FiniteSets

module. . . . . . . . . . . . . . . . . . . 341

18.3 The standard

Bags

module. . . . . . . . . . . . . . . . . . . . . . 343

18.4 The

Peano

module. . . . . . . . . . . . . . . . . . . . . . . . . . . 345

18.5 The

ProtoReals

module . . . . . . . . . . . . . . . . . . . . . . . . 346

18.6 The standard

Naturals

module. . . . . . . . . . . . . . . . . . . . 348

18.7 The standard

Integers

module. . . . . . . . . . . . . . . . . . . . 348

18.8 The standard

Reals

module. . . . . . . . . . . . . . . . . . . . . . 348

Tables

Table 1 The constant operators. . . . . . . . . . . . . . . . . . . . . . 268

Table 2 Miscellaneous constructs. . . . . . . . . . . . . . . . . . . . . 269

Table 3 Action operators. . . . . . . . . . . . . . . . . . . . . . . . . . 269

Table 4 Temp oral operators. . . . . . . . . . . . . . . . . . . . . . . . 269

Table 5 User-denable op erator symbols. . . . . . . . . . . . . . . . . 270

Table 6 The precedence ranges of operators. . . . . . . . . . . . . . . 271

Table 7 Operators dened in the standard mo dules. . . . . . . . . . . 272

Table 8 The

ascii

representations of typeset symbols. . . . . . . . . . 273

properties that we don't consider, including p erformance properties. Worst-

case p erformance can often be expressed as a behavioral prop erty|for example,

Chapter 9 explains how to specify that a system must react within a certain

length of time. However, specifying average p erformance is beyond the scop e of

the metho ds describ ed here.

Our basic to ol for writing specications is mathematics. Mathematics is

nature's way of letting you know how sloppy your writing is. It's hard to be

precise in an imprecise language like English or Chinese. In engineering, impre-

cision can lead to errors. Toavoid errors, science and engineering have adopted

mathematics as their language.

The mathematics we use is more formal than the math you've grown up

with. Formal mathematics is nature's way of letting you know how sloppy

your mathematics is. The mathematics written by most mathematicians and

scientists is not really precise. It's precise in the small, but imprecise in the large.

Each equation is a precise assertion, but you have to read the accompanying

words to understand how the equations relate to one another and exactly what

the theorems mean. Logicians have developed ways of eliminating those words

and making the mathematics completely formal and, hence, completely precise.

Most mathematicians and scientists think that formal mathematics, without

words, is long and tiresome. They're wrong. Ordinary mathematics can be

expressed compactly in a precise, completely formal language. It takes only

about two dozen lines to dene the solution to an arbitrary dierential equation

in the

DierentialEquations

module of Chapter 11. But few specications need

such sophisticated mathematics. Most require only simple application of a few

standard mathematical concepts.

Why TLA

We specify a system by describing its allowed behaviors|what it maydointhe

course of an execution. In 1977, Amir Pnueli introduced the use of temp oral

logic for describing system behaviors. In principle, a system could b e describ ed

by a single temp oral logic formula. In practice, it couldn't. Pnueli's temp oral

logic was ideal for describing some prop erties of systems, but awkward for others.

So, it was usually combined with a more traditional way of describing systems.

In the late 1980's, I invented TLA, the Temp oral Logic of Actions|a simple

variantofPnueli's original logic. TLA makes it practical to describ e a system by

a single formula. Most of a TLA specication consists of ordinary,nontemporal

mathematics. Temp oral logic plays a signicant role only in describing those

properties that it's go od at describing. TLA also provides a nice way to formalize

the style of reasoning ab out systems that has proved to be most eective in

practice|a style known as

assertional

reasoning. However, this book is about

specication; it says almost nothing about pro ofs.

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TLA+规格说明：硬件与软件工程师的语言与工具

Specifying Systems.pdf

It is impossible to add a non-nullable field 'first_name' to customer without specifying a default. This is because the database needs something to populate existing rows.

如何解决 It is impossible to add a non-nullable field 'contact_id' to customercontact without specifying a default. This is because the database needs something to populate existing rows.

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Convert excel format exception.You can try specifying the 'excelType' yourself

It is impossible to add a non-nullable field 'customer' to customercontact without specifying a default. This is because the database needs something to populate existing rows. Please select a fix: 1) Provide a one-off default now (will be set on all existing rows with a null value for this column)

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