Synchronous Programming Of Reactive Systems

This book will attempt to give a first synthesis of recent works con cerning reactive system design. The term "reactive system" has been introduced in order to at'oid the ambiguities often associated with by the term "real-time system," which, although best known and more sugges tive, has been given so many different meanings that it is almost in evitably misunderstood. Industrial process control systems, transporta tion control and supervision systems, signal-processing systems, are ex amples of the systems we have in mind. Although these systems are more and more computerized, it is sur prising to notice that the problem of time in computer science has been studied only recently by "pure" computer scientists. Until the early 1980s, time problems were regarded as the concern of performance evalu ation, or of some (unjustly scorned) "industrial computer engineering," or, at best, of operating systems. A second surprising fact, in contrast, is the growth of research con cerning timed systems during the last decade. The handling of time has suddenly become a fundamental goal for most models of concurrency. In particular, Robin Alilner 's pioneering works about synchronous process algebras gave rise to a school of thought adopting the following abstract point of view: As soon as one admits that a system can instantaneously react to events, i. e.

Reactive systems and event-driven architecture are becoming indispensable to application design, and companies are taking note. Reactive systems ensure that applications are responsive, resilient, and elastic no matter what failures or errors may be occurring, while event-driven architecture offers a flexible and composable option for distributed systems. This practical book helps Java developers bring these approaches together using Quarkus 2.x, the Kubernetes-native Java framework. Clement Escoffier and Ken Finnigan show you how to take advantage of event-driven and reactive principles to build robust distributed systems, reducing latency and increasing throughput, particularly in microservices and serverless applications. You'll also get a foundation in Quarkus to help you create true Kubernetes-native applications for the cloud. Understand the fundamentals of reactive systems and event-driven architecture Learn how to use Quarkus to build reactive applications Combine Quarkus with Apache Kafka or AMQP to build reactive systems Develop microservices that utilize messages with Quarkus for use in event-driven architectures Learn how to integrate external messaging systems, such as Apache Kafka, with Quarkus Build applications with Quarkus using reactive systems and reactive programming concepts

This book is based upon work done under the project "Correct Software through Formal Methods" supported by the German Ministry of Research and Technology. As a case-study report on the practice of formal software development, this book systematically presents and compares 18 different approaches to the control of a real-world production cell. Mathematically precise, formal methods play an increasingly important role in software development, particularly in areas where failure of software would result in injury to people or, at best, significant loss of money. By analyzing the benefits and explaining the use and limitations of formal methods on a sample basis, this book provides a roadmap for the selection and application of appropriate approaches and thus helps in putting formal methods into industrial use.

I am very pleased to play even a small part in the publication of this book on the SIGNAL language and its environment POLYCHRONY. I am sure it will be a s- ni?cant milestone in the development of the SIGNAL language, of synchronous computing in general, and of the data?ow approach to computation. In data?ow, the computation takes place in a producer–consumer network of - dependent processing stations. Data travels in streams and is transformed as these streams pass through the processing stations (often called ?lters). Data?ow is an attractive model for many reasons, not least because it corresponds to the way p- duction,transportation,andcommunicationare typicallyorganizedin the real world (outside cyberspace). I myself stumbled into data?ow almost against my will. In the mid-1970s, Ed Ashcroft and I set out to design a “super” structured programming language that, we hoped, would radically simplify proving assertions about programs. In the end, we decided that it had to be declarative. However, we also were determined that iterative algorithms could be expressed directly, without circumlocutions such as the use of a tail-recursive function. The language that resulted, which we named LUCID, was much less traditional then we would have liked. LUCID statements are equations in a kind of executable temporallogic thatspecifythe (time)sequencesof variablesinvolvedin aniteration.

A man may imagine he understands something, but still not understand anything in the way that he ought to. (Paul of Tarsus, 1 Corinthians 8:2) Calling this a ‘practical theory’ may require some explanation. Theory and practice are often thought of as two di?erent worlds, governed bydi?erentideals,principles, andlaws.DavidLorgeParnas, forinstance,who hascontributedmuchtoourtheoreticalunderstandingofsoftwareengineering and also to sound use of theory in the practice of it, likes to point out that ‘theoretically’ is synonymous to ‘not really’. In applied mathematics the goal is to discover useful connections between these two worlds. My thesis is that in software engineering this two-world view is inadequate, and a more intimate interplay is required between theory and practice. That is, both theoretical and practical components should be integrated into a practical theory. It should beclearfrom theabovethattheintended readership of this book is not theoreticians. They would probably have di?culties in appreciating a book on theory where the presentation does not proceed in a logical sequence from basic de?nitions to theorems and mathematical proofs, followed by - plication examples. In fact, all this would not constitute what I understand by a practical theory in this context.

In today’s app-driven era, when programs are asynchronous and responsiveness is so vital, reactive programming can help you write code that’s more reliable, easier to scale, and better-performing. With this practical book, Java developers will first learn how to view problems in the reactive way, and then build programs that leverage the best features of this exciting new programming paradigm. Authors Tomasz Nurkiewicz and Ben Christensen include concrete examples that use the RxJava library to solve real-world performance issues on Android devices as well as the server. You’ll learn how RxJava leverages parallelism and concurrency to help you solve today’s problems. This book also provides a preview of the upcoming 2.0 release. Write programs that react to multiple asynchronous sources of input without descending into "callback hell" Get to that aha! moment when you understand how to solve problems in the reactive way Cope with Observables that produce data too quickly to be consumed Explore strategies to debug and to test programs written in the reactive style Efficiently exploit parallelism and concurrency in your programs Learn about the transition to RxJava version 2

Reactive systems are computing systems which are interactive, such as real-time systems, operating systems, concurrent systems, control systems, etc. They are among the most difficult computing systems to program. Temporal logic is a formal tool/language which yields excellent results in specifying reactive systems. This volume, the first of two, subtitled Specification, has a self-contained introduction to temporal logic and, more important, an introduction to the computational model for reactive programs, developed by Zohar Manna and Amir Pnueli of Stanford University and the Weizmann Institute of Science, Israel, respectively.

The correct development of large / com plex pieces of software demands a thorough structuring of the design process. In a first phase the requirements engineering is relevant for capturing the relevant functionality and its adequate formalization in precise mathematical definitions. Prototyping can can be used as a means for checking the functional behaviour at this early stage of development. The ade quate specification resulting from the first phase is then the basis for the second phase which comprises the derivation of an implementation. This phase requires the use of formal methods and tools to verify/validate the implementation. A prerequisite for applying this approach is to have a suitable mechanical support. This volume contains the proceedings of the International Workshop Tool Support for System Specification, Development and Verification organized June 1 - 4, 1998, in Malente, Germany. This workshop is the third in a series of events devoted to this topic. The first two workshops were held in 1994 in Kiel and 1996 in Bremen, Germany. The aim of this workshop is to provide a forum for researchers interested in the use and development of tools which support the use of mathematical techniques for the specification, development and verification of systems. The workshop covers the spectrum from verification tools to graphical editors and compilers. The program of the workshop included an invited lecture and 26 talks. The invited lecture was given by F.W. von Henke (University ofUlm) on Mechanized formal methods and system design.