Object-oriented Implementation Research Articles

A Synchronous Scheduling Service for Distributed Real-Time Java

Current trends in real-time systems identify Java as a new alternative to develop both centralized and distributed real-time systems. Many efforts have been devoted to develop the Real-Time Specification for Java (RTSJ), and there is substantial ongoing activity to produce a straightforward and valuable Distributed Real-Time Specification for Java (DRTSJ). The current paper provides a contribution to this latter activity defining, from different angles, a synchronous scheduling service aligned with principles of some popular real-time architectures. This service orchestrates the system in such a way that it provides end-to-end guarantees in the distributed transactions, guaranteeing their timely execution across the network and nodes. The service is described from two points of view: the system one, characterizing a portable model; and the programmer one, defining a distributed object-oriented implementation of a model based on Real-Time Remote Method Invocation (RTRMI). Finally, it also presents results of an implementation carried out to judge the efficiency of the service, offering a preliminary predictability and performance assessment of a distributed real-time Java technology.

Reusing design experiences to materialize software architectures into object-oriented designs

Software architectures capture early design decisions about a system in order to fulfill relevant quality attributes. When moving to detailed design levels, the same architecture can accept many different object-oriented implementations. A common problem here is the mismatches between the quality-attribute levels prescribed by the architecture and those realized by its object-oriented materialization. A significant step towards reducing those mismatches is the provision of tool support for assisting developers in the materialization of software architectures. Prerequisites to develop materialization tools are the organization of a body of design knowledge and the definition of quality-driven reasoning procedures. Since materialization activities are mainly driven by past developers’ experiences, we propose a Case-based Reasoning (CBR) approach that, through the codification of design experiences, permits to establish links between software architecture structures and object-oriented counterparts. This approach is supported by an Eclipse-based tool, called SAME (Software Architecture Materialization Environment), which is a reuse-oriented assistant to the developer. SAME is able to recall and adapt successful architecture materializations for particular quality attributes, in order to help the developer to derive an appropriate object-oriented design for his/her architecture.

An Object-Oriented Framework for Statistical Simulation: TheRPackagesimFrame

Simulation studies are widely used by statisticians to gain insight into the quality of developed methods. Usually some guidelines regarding, e.g., simulation designs, contamination, missing data models or evaluation criteria are necessary in order to draw meaningful conclusions. The R package <b>simFrame</b> is an object-oriented framework for statistical simulation, which allows researchers to make use of a wide range of simulation designs with a minimal effort of programming. Its object-oriented implementation provides clear interfaces for extensions by the user. Since statistical simulation is an embarrassingly parallel process, the framework supports parallel computing to increase computational performance. Furthermore, an appropriate plot method is selected automatically depending on the structure of the simulation results. In this paper, the implementation of <b>simFrame</b> is discussed in great detail and the functionality of the framework is demonstrated in examples for different simulation designs.

Object-Oriented Embedded C

This paper presents an object-oriented implementation of ANSI-C for embedded systems. It offers practical guidelines for producing generic software libraries and portable applications. While various object-oriented implementations of C is available, the aim is to impress a culture of producing safe, robust embedded software which can easily be shared and integrated amongst developers and systems. Starting from coding standards, a design philosophy is proposed for creating reusable drivers, services, applications and finally, a complete real-time operating system.

Empirical assessment of object-oriented implementations with multiple inheritance and static typing

Object-oriented languages involve a threefold tradeoff between runtime efficiency, expressiveness (multiple inheritance), and modularity, i.e. open-world assumption (OWA). Runtime efficiency is conditioned by both the implementation technique and compilation scheme . The former specifies the data structures that support method invocation, attribute access and subtype testing. The latter consists of the production line of an executable from the source code. Many implementation techniques have been proposed and several compilation schemes can be considered from fully global compilation under the closed-world assumption (CWA) to separate compilation with dynamic loading under the OWA, with midway solutions. This article reviews a significant subset of possible combinations and presents a systematic, empirical comparison of their respective efficiencies with all other things being equal . The testbed consists of the Prm compiler that has been designed for this purpose. The considered techniques include C++ subobjects, coloring, perfect hashing, binary tree dispatch and caching. A variety of processors were considered. Qualitatively, these first results confirm the intuitive or theoretical abstract assessments of the tested approaches. As expected, efficiency increases as CWA strengthens. From a quantitative standpoint, the results are the first to precisely compare the efficiency of techniques that are closely associated with specific languages like C++ and Eiffel. They also confirm that perfect hashing should be considered for implementing Java and .Net interfaces.

Object-oriented implementation of 3D DC adaptive finite-element method

In this paper, we introduced a clear object-oriented framework to implement the complicated adaptive procedure with C ++ programming language. In this framework, it consisted of the unstructured mesh generation, a-posterior error estimating, adaptive strategy, and the postprocessing. Unlike the procedure-oriented framework, which is commonly used in DC resistivity modeling with FORTRAN language, the object-oriented one, which is famous for its characteristic of encapsulation, could be used for a class of problems that would be executed by only making some changes on the user interface. To validate its flexibility, two synthetic DC examples were tested here.

Object-oriented design and implementation for multi-type mixed operation

Through studying multi-type arithmetic in many systems, it is found that the existing solutions are not flexible. Process-oriented solution and two potential object-oriented solutions were given and their shortages were analyzed. To achieve flexibility, reusability, maintainability and efficiency, a two-layer virtual table object-oriented solution was proposed based on agile design policy and the Open-Closed Principle (OCP). Analysis shows that the solution is relatively good.

Fuzzy Timed Agent Based Petri Nets for Modeling Cooperative Multi-Robot Systems

A cooperative multi-robot system (CMRS) modeling method called fuzzy timed agent based Petri nets (FTAPN) is proposed in this paper, which has been extended from fuzzy timed object-oriented Petri net (FTOPN). The proposed FTAPN can be used to model and illustrate both the structural and dynamic aspects of CMRS, which is a typical multi-agent system (MAS). At the same time, supervised learning is supported in FTAPN. As a special type of high-level object, agent is introduced into FTAPN, which is used as a common modeling object in its model. The proposed FTAPN can not only be used to model CMRS and represent system aging effect, but also be refined into the object-oriented implementation easily. At the same time, it can also be regarded as a conceptual and practical artificial intelligence (AI) tool for multi-agent systems (MAS) into the mainstream practice of the software development.

Parallel modal analysis with concurrent distributed objects

This paper presents a novel object-oriented implementation of component mode synthesis and mode superposition for dynamic finite element analysis. Interfaces are used extensively to maximize program maintainability and flexibility. Parallelization is achieved using ‘concurrent distributed objects’ (facilitated by Microsoft.NET) instead of the message passing approach. The methodology allows consistency in modelling and implementation; this eases program development. It also results in better program portability across memory architectures. Tests on a cluster of computers and on a shared memory multi-core machine demonstrate the effectiveness of the proposed implementation.

Linking Event-B and Concurrent Object-Oriented Programs

The Event-B method is a formal approach to modelling systems, using refinement. Initial specification is done at a high level of abstraction; detail is added in refinement steps as the development proceeds toward implementation. In software systems that use concurrent processing it is necessary to provide details of concurrent features before implementation. Our contribution is to show how Event-B models can be linked to concurrent, object-oriented implementations using an intermediate, object-oriented style specification notation. To validate our approach and gain further insight we automated the translation process with an Eclipse plug-in which produces an Event-B model and Java code. We call the new notation Object-oriented Concurrent-B (OC-B). The notation facilitates specification of the concurrent aspects of a development, and facilitates reasoning about concurrency issues in an abstract manner. We abstract away implementation details, such as locking, and provide the developer with a clear view of atomicity using labelled atomic clauses. We build on techniques introduced in UML-B to model object-oriented developments, introducing non-atomic operations and features for specifying implementation level details.

Generic limnological models on the touchstone: Testing the lake simulation library SALMO-OO and the rule-based Microcystis agent for warm-monomictic hypertrophic lakes in South Africa

Generic models are required to share models for the same category of ecosystems in order to facilitate comparative scenario analyses and forecasting, and classify ecosystem health. However, generality is the most often neglected one of the three criteria for model validation: reality, precision and generality. The paper suggests to validate models for lake ecosystem categories defined by (a) circulation types of lakes that to some degree reflect climate and morphometry, and (b) trophic states of lakes that to some degree reflect community structures and habitat properties. Two models are tested for South African lakes belonging to the category of warm-monomictic and hypertrophic lakes: the deterministic simulation library SALMO-OO and a rule-based agent for Microcystis discovered by evolutionary computation. SALMO-OO is an object-oriented implementation of mass balance equations for a typical pelagic food web (diatoms, green algae, blue-green algae, and cladocerans) and nutrient cycles (PO 4-P, NO 3-N, detritus) as well as alternative process models for algal growth and grazing, zooplankton growth and mortality. During validation the best performing model structure is determined for a number of lakes belonging to the same category. SALMO-OO is implemented in JAVA providing an interactive user-interface. The rule-based Microcystis agent has been discovered by the hybrid evolutionary algorithm HEA after training by merged time series data of three lakes belonging to the same category and 14-fold cross-validation for data of all 14 years of each lake. The agent allows 7-days-ahead forecasting of Microcystis abundance for any of the three lakes. It can be concluded that the design and validation of models for ecosystem categories improves the generality of models, and promotes both model as well as data sharing. Future work will focus on distinctive ecological features of ecosystem categories to be considered in informed structure design and validation of category models.

Process-based simulation library SALMO-OO for lake ecosystems. Part 1: Object-oriented implementation and validation

The process-based simulation library SALMO-OO represents an object-oriented implementation of mass balance equations for pelagic food webs consisting of diatoms, green algae, blue-green algae and cladocerans, as well as nutrient cycles based on PO 4–P, NO 3–N, DO and detritus in lakes. It gains its structural flexibility from alternative process representations for algal growth and grazing, and zooplankton growth and mortality. Generic model structures of SALMO-OO were determined for three lake categories classified by circulation types reflecting the local climate and morphometry of lakes, and by trophic states reflecting community structures and habitat properties of lakes. Data of six lakes belonging to either of the three lake categories were used to validate the lake category specific structures of SALMO-OO. The study has demonstrated that: (1) JAVA suits well for object-oriented implementations of ecological simulation libraries, (2) object-oriented simulation libraries facilitate the identification of generic model structures for ecosystem categories.

An object-oriented cellular automata model for forest planning problems

Various difficulties are encountered when integrating spatial and temporal goals of forest planning with dynamics of natural processes. Some of these difficulties stem from the difference between the data and models involved in the various processes to be integrated. The focus of this study is the development of a decentralized spatial decision support tool for forest management planning based on cellular automata (CA) modeling. An innovation of this model is that beyond spatially allocating/simulating management activities, the CA rules and state space are modified to allow cells to co-evolve until a plan for all periods of the planning horizon has been achieved. The object-oriented implementation of the CA model in a geographic information system (GIS) is presented as a decentralized bottom-up forest planning approach. Moreover, a sensitivity analysis of the model outcomes to spatial resolution and objective weights is performed. This planning tool effectively addresses local spatial constraints (limitation on the type of management depending on location), global spatial objectives (spatial clustering of old growth conservation areas), global aspatial objectives (timber harvest) and global constraints (stable flow and minimum old growth conservation). The capability of this approach to consider spatial relationships in the strategic planning process is illustrated by a spatially consistent allocation of clustered old growth areas. The object orientation of the implementation permits a fast computation of both local and global limitations on local decision making. This framework allows speedy modification of either local or global requirements and is highly portable to other complex planning problems.

Accurate numerical derivatives in MATLAB

Complex step differentiation (CSD) is a technique for computing very accurate numerical derivatives in languages that support complex arithmetic. We describe here the development of a CSD package in MATLAB called PMAD. We have extended work done in other languages for scalars to the arrays that are fundamental to MATLAB. This extension raises questions that we have been able to resolve in a satisfactory way. Our goal has been to make it as easy as possible to compute approximate Jacobians in MATLAB that are all but exact. Although PMAD has a fast option for the expert that implements CSD as in previous work, the default is an object-oriented implementation that asks very little of the user.

Flux-based contaminant transport in a GIS environment

A computationally efficient method for predicting contaminant mass flux to a specified boundary is presented. The method combines streamlines calculated using the analytic element method with a first-passage-time (residence time) approach to calculating mass flux. Computations exploit convolution in Laplace space with numerical inversion. The technique is carried out in a geographic information system (GIS) that takes full advantage of widely available digital hydrologic data. The flux-based estimations allow efficient coupling of contaminant mass across hydrologic interfaces. This combined approach is useful for rapid but approximate transport computations either at the local or regional scale. We demonstrate the approach by considering nitrogen-loading to surface water due to surface application of animal feedlot waste. Nitrogen is predicted to migrate through ground-water, resulting in a long-term loading to nearby streams. The object-oriented implementation of this modeling approach improves integration between the GIS and the transport modeling, allowing transport results to be returned to the database.

Object-Oriented Representation of Environmental Phenomena: Is Everything Best Represented as an Object?

A geographic space must be partitioned into a finite number of discrete pieces, such as points, lines, polygons, and grid cells, to accommodate the finite computing environment. Because these discrete geometric primitives can be implemented as software objects, the object-oriented computing paradigm might have encouraged the tendency to “objectify” spatial phenomena, regardless of whether they are best represented as objects. A critical review is necessary to assess whether object-orientation, a concept first developed outside geography, is suitable for spatial representation. This article reviews object-oriented spatial representation in the context of environmental modeling. The review is organized into four topics: (1) the principles underlying object-orientation, (2) the categorization of environmental phenomena, (3) GIS data models and their object-oriented implementation, and (4) the compatibility between these three sets of concepts. The discussion argues that spatial objects, regions, and fields represent three categories of phenomena that are well represented, reasonably represented, and not well represented by the objects, respectively.

Refactoring OCL annotated UML class diagrams

Refactoring of UML class diagrams is an emerging research topic and heavily inspired by refactoring of program code written in objectoriented implementation languages. Current class diagram refactoring techniques concentrate on the diagrammatic part but neglect OCL constraints that might become syntactically incorrect by changing the underlying class diagram. This paper formalizes the most important refactoring rules for class diagrams and classifies them with respect to their impact on attached OCL constraints. For refactoring rules that have an impact on OCL constraints, we formalize the necessary changes of the attached constraints. Our refactoring rules are specified in a graph-grammar inspired formalism. They have been implemented as QVT transformation rules. We finally discuss for our refactoring rules the problem of syntax preservation and show, by using the KeY-system, how this can be resolved.

Object oriented implementation of distributed finite element analysis in .NET

The paper describes a detailed study into the object-oriented implementation of distributed finite element analysis on desktop computers using the .NET framework. The software design aspects are described in some detail for both direct and iterative solution algorithms. The use of interfaces played an important role in the software design. This, together with the .NET framework, enabled remote objects to be implemented in a relatively seamless fashion. The solution routines were “blind” to whether the objects were local or remote. Numerical tests were carried out and reasonable speed-up was achieved, particularly for direct solution methods. It is concluded that .NET provides a viable framework for implementing distributed computing on networks of personal computers.

TeMAS–a multi-agent system for temporally rich domains

In this paper, we present the model and simulator of a multi-agent system (MAS) for temporally rich domains. The theoretical foundations of the model include a knowledge representation scheme based on an original modification of Petri nets, called Petri nets with time tokens (PNTTs), as well as temporal reasoning based on the extension of Allen's temporal logic. The proposed MAS, called TeMAS, has a hierarchical structure, consisting of different levels, where each level contains clusters of agents. A paradigm of hierarchically organized blackboards is used for the communication among agents, clusters, as well as levels. We describe an object-oriented implementation of a program simulator of TeMAS and give an example of the use of the simulator for interpretation of events in a dynamic scene.

Q uaff: efficient C++ design for parallel skeletons

We present Q uaff, a new skeleton-based parallel programming library. Its main originality is to rely on C++ template meta-programming techniques to achieve high efficiency. In particular, by performing most of skeleton instantiation and optimization at compile-time, Q uaff can keep the overhead traditionally associated to object-oriented implementations of skeleton-based parallel programming libraries very small. This is not done at the expense of expressivity. This is demonstrated in this paper by several applications, including a full-fledged, realistic real-time vision application.