Declarative Programming Style Research Articles

Veracity: declarative multicore programming with commutativity

There is an ongoing effort to provide programming abstractions that ease the burden of exploiting multicore hardware. Many programming abstractions ( e.g. , concurrent objects, transactional memory, etc.) simplify matters, but still involve intricate engineering. We argue that some difficulty of multicore programming can be meliorated through a declarative programming style in which programmers directly express the independence of fragments of sequential programs. In our proposed paradigm, programmers write programs in a familiar, sequential manner, with the added ability to explicitly express the conditions under which code fragments sequentially commute. Putting such commutativity conditions into source code offers a new entry point for a compiler to exploit the known connection between commutativity and parallelism. We give a semantics for the programmer’s sequential perspective and, under a correctness condition, find that a compiler-transformed parallel execution is equivalent to the sequential semantics. Serializability/linearizability are not the right fit for this condition, so we introduce scoped serializability and show how it can be enforced with lock synthesis techniques. We next describe a technique for automatically verifying and synthesizing commute conditions via a new reduction from our commute blocks to logical specifications, upon which symbolic commutativity reasoning can be performed. We implemented our work in a new language called Veracity, implemented in Multicore OCaml. We show that commutativity conditions can be automatically generated across a variety of new benchmark programs, confirm the expectation that concurrency speedups can be seen as the computation increases, and apply our work to a small in-memory filesystem and an adaptation of a crowdfund blockchain smart contract.

Genetic Algorithms in a Visual Declarative Programming

mperative languages like Java, C++, and Python are mostly used for the implementation of Genetic algorithms (GA). Other programming paradigms are far from being an object of study. The paper explores the advantages of a new non-mainstream programming paradigm, with declarative and nondeterministic features, in the implementation of GA. Control Network Programming (CNP) is a visual declarative style of programming in which the program is a set of recursive graphs, that are graphically visualized and developed. The paper demonstrates how the GA can be implemented in an automatic, i.e. non-procedural (declarative) way, using the built-in CNP inference mechanism and tools for its control. The CNP programs are easy to develop and comprehend, thus, CNP can be considered a convenient programming paradigm for efficient teaching and learning of nondeterministic, heuristic, and stochastic algorithms, and in particular GA. The outcomes of using CNP in delivering a course on Advanced Algorithm Design are shown and analyzed, and they strongly support the positive results in teaching when CNP is applied.

Veracity: Declarative Multicore Programming with Commutativity

There is an ongoing effort to provide programming abstractions that ease the burden of exploiting multicore hardware. Many programming abstractions (e.g., concurrent objects, transactional memory, etc) simplify matters, but still involve intricate engineering. We argue that some difficulty of multicore programming can be meliorated through a declarative programming style in which programmers directly express the independence of fragments of sequential programs. In our proposed paradigm, programmers write programs in a familiar, sequential manner, with the added ability to explicitly express the conditions under which code fragments commute. Putting such commutativity conditions into source code offers a new entry point to exploit the known connection between commutativity and parallelism. We give sequential and concurrent semantics for commute statements, as well as a correctness condition called scoped serializability and discuss how it can be enforced when combined with commutativity conditions. We next describe a technique for automatically synthesizing commute conditions directly from source code via a new reduction to commutativity of object methods. We implemented our work in a new language called Veracity, implemented in Multicore OCaml and on top of Servois and the libcuckoo concurrent hashtable. We provide the first benchmarks programs with commute blocks. We show that commute conditions can be synthesized even for non-linear programs; we confirm the expectation that concurrency speedups can be seen as the computation increases; and we apply our work to a small in-memory filesystem and a crowdfund blockchain smart contract.

Declarative Programming with Intensional Sets in Java Using JSetL

Abstract Intensional sets are sets given by a property rather than by enumerating their elements. In a previous work, we have proposed a decision procedure for a first-order logic language which provides restricted intensional sets (RISs), i.e. a sub-class of intensional sets that are guaranteed to denote finite—though unbounded—sets. In this paper, we show how RIS can be exploited as a convenient programming tool also in a conventional setting, namely the imperative O-O language Java. We do this by considering a Java library, called JSetL, that integrates the notions of logical variable, (set) unification and constraints that are typical of constraint logic programming languages into the Java language. We show how JSetL is naturally extended to accommodate for RIS and RIS constraints and how this extension can be exploited; on the one hand, to support a more declarative style of programming and, on the other hand, to effectively enhance the expressive power of the constraint language provided by the library.

The Importance of Being Declarative

A declarative programming style focuses on what you want your program to do rather than how to perform the task. Through diverse programming techniques, libraries, and specialized languages, you end up with code that sidesteps nitty-gritty implementation details, dealing instead with a task's big picture.

JSetL: a Java library for supporting declarative programming in Java

AbstractIn this paper we present a Java library—called JSetL—that offers a number of facilities to support declarative programming such as those usually found in logic or functional declarative languages: logical variables, list and set data structures (possibly partially specified), unification and constraint solving over sets, non‐determinism. The paper describes the main features of JSetL and it shows, through a number of simple examples, how these features can be exploited to support a real declarative programming style in Java. Copyright © 2006 John Wiley & Sons, Ltd.

R++: adding path-based rules to C++

Object-oriented languages and rule-based languages offer two distinct and useful programming abstractions. However, previous attempts to integrate data-driven rules into object-oriented languages have typically achieved an uneasy union at best. R++ is a new, closer integration of the rule-based and object-oriented paradigms that extends C++ with a single programming construct, the path-based rule, as a new kind of class member. Path-based rules-data-driven rules that are restricted to following pointers between objects-are like automatic methods that are triggered by changes to the objects they monitor. Path-based rules provide a useful level of abstraction that encourages a more declarative style of programming and are valuable in object-oriented designs as a means of modeling dynamic collections of interdependent objects. Unlike more traditional pattern-matching rules, path-based rules are not at odds with the object-oriented paradigm and offer performance advantages for many natural applications.

Managing semistructured data with FLORID: A deductive object-oriented perspective

The closely related research areas management of semistructured data and languages for querying the Web have recently attracted a lot of interest. We argue that languages supporting deduction and object-orientation (dood languages) are particularly suited in this context: Object-orientation provides a flexible common data model for combining information from heterogeneous sources and for handling partial information. Techniques for navigating in object-oriented databases can be applied to semistructured databases as well, since the latter may be viewed as (very simple) instances of the former. Deductive rules provide a powerful framework for expressing complex queries in a high-level, declarative programming style. We elaborate on the management of semistructured data and show how reachability queries involving general path expressions and the extraction of data paths in the presence of cyclic data can be handled. We then propose a formal model for querying structure and contents of Web data and present its declarative semantics. A main advantage of our approach is that it brings together the above-mentioned issues in a unified, formal framework and—using the Florid system—supports rapid prototyping and experimenting with all these features. Concrete examples illustrate the concise and elegant programming style supported by Florid and substantiate the above-mentioned claims.

An overview of the Flagship system

AbstractThe Flagship Project1 was a research collaboration between the University of Manchester, Imperial College London and International Computers Ltd. The project was unusual in that it aimed to produce a complete computing system based on a declarative programming style. Three areas of a declarative system were addressed: (1) programming languages and programming environments; (2) the machine architecture and computational models; and (3) the software environment. This overview paper discusses each of these areas, the intention being to present the project as a coherent whole.

Constraint-based languages and systems (abstract)

A constraint is a relation that should be satisfied, for example, that a line remain horizontal, that a resistor in an electrical circuit simulation obey Ohms Law, or that the height of a bar in a bar chart be proportional to some number in an application program. Constraints have been used in a variety of languages and systems, particularly in user interface tool kits, in planning and scheduling, and in simulation. They provide an intuitive declarative style of programming that integrates well with object-oriented systems. This tutorial teaches what constraints are, how to use them in applications such as user interfaces, how to implement them (including how to implement constraint hierarchies), and how to embed them in object-oriented and logic programming languages. You dont have to know anything about constraints, but it would be helpful to have a strong background in programming languages.

CLP(?) and some electrical engineering problems

The Constraint Logic Programming Scheme defines a class of languages designed for programming with constraints using a logic programming approach. These languages are soundly based on a unified framework of formal semantics. In particular, as an instance of this scheme with real arithmetic constraints, the CLP(ℜ) language facilitates and encourages a concise and declarative style of programming for problems involving a mix of numeric and non-numeric computation. In this paper we illustrate the practical applicability of CLP(ℜ) with examples of programs to solve electrical engineering problems. This field is particularly rich in problems that are complex and largely numeric, enabling us to demonstrate a number of the unique features of CLP(ℜ). A detailed look at some of the more important programming techniques highlights the ability of CLP(ℜ) to support well-known, powerful techniques from constraint programming. Our thesis is that CLP(ℜ) is an embodiment of these techniques in a language that is more general, elegant and versatile than the earlier languages, and yet is practical.

COMPLEX: an object-oriented logic programming system

The design and a prototypical implementation of COMPLEX, which is a logic-based system extended with concepts from the object-oriented paradigm and is intended as a tool for the development of knowledge-based applications, are described. The system supports a logic language, called Complex-Datalog (C-Datalog), enhanced by semantic constructs to provide facility for data abstraction. Its implementation is based on a bottom-up computational model that guarantees a fully declarative style of programming. However, the user is also given the possibility of running a query using a top-down model of computation. Efficiency of execution is the result of the integration of different novel technologies for the compilation and the execution of queries. >

A declarative state transition system

Most declarative formalisms do not support changes to the program state. In consequence, the benefits of a declarative programming style cannot be realized when writing state-changing programs such as environments and programming tools. Backus proposes applicative state transition systems as a solution to this problem. In such systems, computation and update are separated: programs are interpreted as defining functions over states, and update follows successful computation of new states. This paper shows how this idea can be used in practice. A class of programming systems termed declarative state transition (DST) systems is defined. A DST system supports program access to state, incremental description of new states, persistence, and atomic, serializable transactions. These features resolve problems inherent in Backus's original proposal. They are made available in an extended declarative language, which supports a declarative treatment of file system update. This user language is used to implement programming environments and tools. The approach is illustrated by a description of the design and application of Parlog+, the user language in a DST system for parallel logic programming.

Implementation of a declarative state‐transition system

AbstractA declarative programming style is claimed to have significant advantages from a software engineering point of view. However, these benefits cannot generally be realized when writing programs that are concerned with changing state, such as environments and programming tools. Declarative state‐transition (DST) systems have been proposed as a solution to this problem. In DST systems, computation and update are separated. Programs are interpreted as defining functions or relations over states, and update follows successful computation of new states. Support for persistent state and atomic, serializable transactions facilitates the implementation of programming environments and tools. This paper describes an implementation scheme for DST systems. The scheme is illustrated by a presentation of the implementation of PPS, a DST system for parallel logic programming.

Flagship: a parallel architecture for declarative programming

The Flagship project aims to produce a computing technology based on the declarative style of programming. A major component of that technology is the design for a parallel machine which can efficiently exploit the implicit parallelism in declarative programs. This paper describes the computational models which expose this implicit parallelism, and outlines an architecture designed to exploit it. The operational issues, such as dynamic load balancing, which arise in such a system are discussed, and the mechanisms being used to evaluate the architecture are described.

Fifth Generation Computing: Introducing Micro-Prolog into the Classroom

The international computer industry is embarked on the construction of anew “Fifth Generation” of computers that are intended to be more accessible to the human user. The Japanese Fifth Generation project is based on the use of “Logic Programming.” In this article the authors describe their use of “Logic Programming” in school classrooms since 1980 and give an account of different styles of introduction for wide-ranging educational applications, using readily available personal computers. Emphasis is placed on clear description and explanation of knowledge areas rather than on the behavior of the computer. This provides an introduction to the use of logic and the declarative style of programming in the context of the traditional school curriculum.