Hierarchy Of Modules Research Articles

On modular termination proofs of general logic programs

We propose a modular method for proving termination of general logic programs (i.e. logic programs with negation). It is based on the notion of acceptable programs, but it allows us to prove termination in a truly modular way. We consider programs consisting of a hierarchy of modules and supply a general result for proving termination by dealing with each module separately. For programs which are in a certain sense well-behaved, namely well-moded or well-typed programs, we derive both a simple verification technique and an iterative proof method. Some examples show how our system allows for greatly simplified proofs.

An efficient register optimization algorithm for high-level synthesis from hierarchical behavioral specifications

We address the problem of register optimization that arises during high-level synthesis from modular hierarchical behavioral specifications. Register optimization is the process of grouping carriers such that each group can be safely allocated to a hardware register. Global register optimization by inline expansion involves flattening the module hierarchy and using a heuristic register optimization procedure on the flattened description. Although inline expansion yields a near-optimal number of registers, it is very time consuming due to the large number of carrier compatibility relationships that must be considered. We present an efficient register optimization algorithm that achieves nearly the same effect of inline expansion without actually inline expanding. The distinguishing feature of the proposed algorithm is that it employs a hierarchical optimization phase which effectively exploits the properties of the module call graph and information gathered during local carrier lifecycle analysis of each module. Experimental results on a number of benchmarks show that the proposed algorithm produces nearly the same number of registers as inline expansion based global optimization and is faster by a factor of 7.0.

Function-class decomposition: a hybrid software engineering method

In addition to offering a simple yet powerful method for decomposing a system, function-class decomposition (FCD) produces an architecture that is more supportive than traditional object-oriented decomposition for several software engineering tasks. A hybrid method that integrates structured analysis with an OO approach, FCD identifies classes in parallel with decomposing the system into a hierarchy of functional modules. Recently, developers extended FCD to integrate UML concepts. Useful for partitioning a system for distribution, the FCD hierarchy provides a framework for controlling development in a distributed software engineering environment. It also helps identify and integrate components in component-based development and supports the system life-cycle maintenance phase. Further, FCD addresses many of the initial analysis and design problems inherent in large and complex OO systems. The authors' experience with testing FCD on several applications validates its compatibility with OO methodologies and modeling techniques.

Designing numerical libraries in Fortran 90

Currently Fortran 77 is the most widely used language for libraries of numerical procedures, although it has many disadvantages for this purpose. Fortran 90 offers significant benefits for both developers and users of numerical libraries, especially: explicit interfaces, dynamic allocation of workspace, assumed-shape arrays, optional arguments, generic interfaces, parameterisation of precision, and derived types. All these features help to simplify the user-interface to procedures. Fortran 90 libraries can be constructed as a hierarchy of modules, with controlled access to entities, which may include type definitions and named constants as well as procedures. The interfaces to procedures may also be defined in terms of operators. Numerical libraries in Fortran 90 are already available from two commercial vendors, NAG and VNI, and numerical software in Fortran 90 has begun to appear in the public domain.

Modular logic programming

Modularity is a key issue in the design of modern programming languages. When designing modular features for declarative languages in general, and for logic programming languages in particular, the challenge lies in avoiding the superimposition of a complex syntactic and semantic structure over the simple structure of the basic language. The modular framework defined here for logic programming consists of a small number of operations over modules which are (meta-) logically defined and semantically justified in terms of the basic logic programming semantics. The operations enjoy a number of algebraic properties, thus yielding an algebra of modules. Despite its simplicity, the suite of operations is shown capable of capturing the core features of modularization: information hiding, import/export relationships, and construction of module hierarchies. A metalevel implementation and a compilation-oriented implementation of the operations are provided and proved sound with respect to the semantics. The compilation-oriented implementation is based on manipulation of name spaces and provides the basis for an efficient implementation.

Nuffield interactive mathematics courseware

Major changes are taking place both in the content of A-Level Mathematics courses and in the style in which they are taught. Modern technology has created opportunities for improving teaching at schools and universities which are desirable in themselves, and which can also help to meet educational pressures for change. The Nuffield Foundation had funded an 18 month pilot project ending June 1993 to study these questions, and develop two experimental modules, Matrices and Data Fitting. Both development and evaluation were carried out in collaboration with several universities, and students from several disciplines were involved. The materials are intended mainly for those who require mathematics as part of another main subject. Materials were written in the hypertext style developed in the Renaissance Project and interactive mathematical and graphical animations were emphasized. From the outset the project addressed the issue of the “not made here” effect through consultation with potential users. The strategy was to design materials in a hierarchy of modules, units and elements to be managed within a highly flexible control structure in such a way that lecturers and teachers could either build their own course, or use preassembled materials out of a “kit of parts”. Lessons learned have provided the basis for the authoring style adopted by the UK Mathematics Courseware Consortium (UKMCC).

Specifying modules to satisfy interfaces: A state transition system approach

We define interface, module and the meaning of M offers I, where M denotes a module and I an interface. For a module M and disjoint interfaces U and L, the meaning of M using L offers U is also defined. For a linear hierarchy of modules and interfaces, M1, I1, M2, I2, ..., Mn, In, we present the following composition theorem: If M1 offers I1 and, for i=2,..., n, Mi using Ii-1 offers Ii, then the hierarchy of modules offers Ii.Our theory is applied to solve a problem posed by Leslie Lamport at the 1987 Lake Arrowhead Workshop. We first present a formal specification of a serializable database interface. We then provide specifications of two modules, one based upon two-phase locking and the other multi-version timestamps; the two-phase locking module uses an interface offered by a physical database. We prove that each module offers the serializable interface.

Modularity and reliability in the organization of organisms.

An organism persists only if it satisfies internal and external constraints. Within the organism networks of processes meet the constraints. In such networks a principle of matching often obtains: the pattern of coupling among processes matches the correlation among constraints. That is, a module-a cluster of coupled processes-meets a constraint. Dissociable modules meet dissociable constraints. A hierarchy of modules meets a hierarchy of constraints. We have inquired whether such matching is predicted by an optimality criterion in a simple example. We find that in an ensemble of networks with unreliable processes, the networks that meet the constraints with highest reliability obey the principle of matching. The difference in reliability between modular and nonmodular networks that meet the same constraints is a function of the probability of success per process. Our results suggest that this difference is maximal at a probability of success that increases monotonically with the number of processes in the network.

A model for parallel training and learning in dynamic structural response analysis

It is the intent of this paper to present a model for parallel training and learning of state characteristics throughout the dynamic response analysis of structures. The central feature of this model will be the capability to acquire knowledge and control the state of the dynamic response characteristics at every step of the analysis. Emphasis will be placed upon: (1) defining and modeling a mechanism for parallel training and learning (PTL) of dynamic structural characteristics, and (2) definition of corresponding processors which will support PTL. Finally a demonstrative example will be presented and conclusions will be discussed. The architecture of the system consists of a hierarchy of intelligent modules, suited for modeling structures. The abstraction levels of the hierarchy are linked by two knowledge layers: general heuristic knowledge and specific-case knowledge layers. The dynamic response state will be described by: (1) dynamic state variables and (2) structural descriptor state variables. Their instantiations will represent the response characteristics of the structure at a given time step. The dynamic response state, at a given time step and specific abstraction level, will be expressed by a feature-vector, composed of representants of all variables. The PTL mechanism will process feature-vectors one time step at a time. Two or more training and learning processes are said to be in parallel when they have a common input feature-vector, whose components are processed independently for the same time step, and their outputs are recombined in order to obtain the transformed feature-vector. Training and learning processes will assist the dynamic analysis at all levels. Their major goal is to identify critical states (e.g. critical values, critical behavior regions) which can lead to partial or total failure mechanisms of analyzed structures. In the present model, the criteria for focusing on critical states of the different structural characteristics will be predefined.

Symbol grounding via a hybrid architecture in an autonomous assembly system

We describe the architectural principles of our somass robotic assembly system. It requires little more information than the shape of the desired assembly and the shape of the parts from which to construct an assembly plan, which is executed reliably by a robot system. It is a hybrid system, comprising a careful marriage of a prolog assembly planning system with a plan execution agent designed to control uncertainty (including the use of sensors) by means of behavioural modules which accomplish useful motions of the parts. The key notions are the simplification of the planner resulting from increasing the competence of the plan execution agent, and grounding the planner through a single hierarchy of behavioural modules instead of a twin hierarchy of sensing and action. We develop new terms for this discussion, since the old ones-such as ''subsymbolic''-beg the questions we wish to address.

Type extensions

Software systems represent a hierarchy of modules. Client modules contain sets of procedures that extend the capabilities of imported modules. This concept of extension is here applied to data types. Extended types are related to their ancestor in terms of a hierarchy. Variables of an extended type are compatible with variables of the ancestor type. This scheme is expressed by three language constructs only: the declaration of extended record types, the type test, and the type guard. The facility of extended types, which closely resembles the class concept, is defined in rigorous and concise terms, and an efficient implementation is presented.

Remarks on the quantization of conformal fields

The quantization of a general ( b, c) system in two dimensions is formulated in terms of an infinite hierarchy of modules for the Virasoro algebra that interpolate between the space of classical conformal fields of weight j and the Dirac sea of semi-infinite forms. This provides a natural framework in which to study the relation between algebraic geometry and representations of the Virasoro algebra with central charge c j =−2(6 j 2−6 j+1). The importance of the construction is discussed in the context of string theory.

Application of AI programming techniques to the analysis of structures

One of the primary objectives of AI is to build systems that are able to enlarge and modify their knowledge base and to profit in an intelligent way from the acquired experience. This paper presents a prototype system that provides the capability of adaptively learning from training experience, a process that is currently carried out by the user when performing a structural analysis. The presented system is based on the development of a hierarchy of intelligent modules, suited for modeling structures. Emphasis is placed upon the following problems: (1) representation of these modules; (2) the relation between them in the modeling process and the flow of information in the analysis process; and (3) defining the concept of training and developing a suitable mechanism of training. The system is written in CPROLOG and runs on a VAX 780. The modular structure of the developed system, as well as the capability to learn from training experience in a dynamic environment, establishes the basis of a formalized methodology for developing training systems which may be extended to include other types of training objectives in the process of structural analysis.

Extension of record types

Software systems represent a hierarchy of modules. Client modules contain sets of procedures that extend the capabilities of imported modules. This concept of extension is here applied to data types. Extended types are related to their ancestor in terms of a set hierarchy. Variables of an extended type form a subset of the variables of the ancestor type. This scheme is easily and efficiently implementable, and is manifest by two new language constructs only: the type test and the type guard.

Fault Tolerance And Self-Healing In Optical Systolic Array Processors

Defining a channel failure in an optical systolic array processor leads to a simple test for failure and an adjustment procedure that will correct minor failures. Noncorrectable, or major, failures must be bypassed when possible or limited in effect when no further bypassing is possible. This analysis leads to the concept of hierarchies of modules in which failures can be detected and either healed or bypassed. Software to detect instantaneous failures is described. Such a detection triggers additional correction by bypassing.

A library of new capabilities in statistical computing

Innovative Information Technology, consultants in statistics, operations research and scientific computing, have developed a library of several dozen main programs and subroutines for multivariate data analysis and display. These are organized into a hierarchy of modules or 'packages'. The liT routines are designed to perform a variety of computations and produce a variety of graphical outputs not generally available in other statistical packages. At present they are organized as follows:

The Production of Program Families Based on Abstract Data Types

The convenience of considering industrial software systems as program families rather than unique programs is argued. Conventional computer aided program manufacturing methods are then discussed and some of their problems are analysed. The paper shows how these problems may be essentially solved by conceiving, implementing and manufacturing programs as hierarchies of Multifunctional Modules or Abstract Data Types. It may be specially useful for applications where data amount and complexity are important.

Optimization of spare parts for hierarchicall decomposable systems

Complex technical systems are often hierarchically composed of exchangeable modules, which themselves may be composed of exchangeable submodules. The hierarchy of modules of such systems can be represented by trees. Defective systems are repaired in a supply depot system by exchanging the defective modules from a stock of spare parts. The exchanged defective modules are repaired for resupply. In this paper, a dynamic programming algorithm for optimizing the stocks of spare parts, under a budget constraint, is presented. The optimization criterion is the minimization of the backlog of entire systems at the supply depot system. An implementation of the algorithm is described and some illustrative examples are given.

On the interpretive mechanisms of microprogrammed systems

In microprogrammable systems a special type of interpretive linkage mechanism is used. This linkage mechanism, among all known interpretive techniques, shows the clearest distinction between linkage implementation and the execution mechanisms of semantics. The essentials of interpretation by micro programs may be used as part of a design guideline for the design of a variety of multi processor systems or multi micro processor systems, aiming hereby at more clearly structured design solutions. After a short discussion of the interpretive mechanisms, known from microprogrammable systems, its possible impact on the design philosophies for hardware design in computer architecture, and for integrated hardware/software design efforts, is the subject of this paper. Especially one particular design philosophy, derived from the interpretive mechanism of microprogrammable systems, is discussed, which results in computer architectures in form of a hierarchy of interpretive modules. A few examples are mentioned.