Current trends in industrial systems opt for the use of different big-data engines as a means to process huge amounts of data that cannot be processed with an ordinary infrastructure. The number of issues an industrial infrastructure has to face is large and includes challenges such as the definition of different efficient architecture setups for different applications, and the definition of specific models for industrial analytics. In this context, this paper explores the development of a medium size big-data engine (i.e., implementation) able to improve the performance in map-reduce computing by splitting the analytic into different segments that may be processed by the engine in parallel using a hierarchical model. This type of facility reduces end-to-end computation time for all segments with their results then merged with other information from other segments after their processing in parallel. This type of setup increases the performance of current clusters improving I/O operations remarkably as empirical results revealed.

The goal of multi-winner elections is to choose a fixed-size committee based on voters’ preferences. An important concern in this setting is representation: large groups of voters with cohesive preferences should be adequately represented by the election winners. Recently, Aziz et al. proposed two axioms that aim to capture this idea: justified representation (JR) and its strengthening extended justified representation (EJR). In this paper, we extend the work of Aziz et al. in several directions. First, we answer an open question of Aziz et al., by showing that Reweighted Approval Voting satisfies JR for k = 3; 4; 5, but fails it for k >= 6. Second, we observe that EJR is incompatible with the Perfect Representation criterion, which is important for many applications of multi-winner voting, and propose a relaxation of EJR, which we call Proportional Justified Representation (PJR). PJR is more demanding than JR, but, unlike EJR, it is compatible with perfect representation, and a committee that provides PJR can be computed in polynomial time if the committee size divides the number of voters. Moreover, just like EJR, PJR can be used to characterize the classic PAV rule in the class of weighted PAV rules. On the other hand, we show that EJR provides stronger guarantees with respect to average voter satisfaction than PJR does.

The term big data occurs more frequently now than ever before. A large number of fields and subjects, ranging from everyday life to traditional research fields (i.e., geography and transportation, biology and chemistry, medicine and rehabilitation), involve big data problems. The popularizing of various types of network has diversified types, issues, and solutions for big data more than ever before. In this paper, we review recent research in data types, storage models, privacy, data security, analysis methods, and applications related to network big data. Finally, we summarize the challenges and development of big data to predict current and future trends.

In recent years, big data systems have become an active area of research and development. Stream processing is one of the potential application scenarios of big data systems where the goal is to process a continuous, high velocity flow of information items. High frequency trading (HFT) in stock markets or trending topic detection in Twitter are some examples of stream processing applications. In some cases (like, for instance, in HFT), these applications have end-to-end quality-of-service requirements and may benefit from the usage of real-time techniques. Taking this into account, the present article analyzes, from the point of view of real-time systems, a set of patterns that can be used when implementing a stream processing application. For each pattern, we discuss its advantages and disadvantages, as well as its impact in application performance, measured as response time, maximum input frequency and changes in utilization demands due to the pattern.

Current infrastructures for developing big-data applications are able to process -via big-data analytics- huge amounts of data, using clusters of machines that collaborate to perform parallel computations. However, current infrastructures were not designed to work with the requirements of time-critical applications; they are more focused on general-purpose applications rather than time-critical ones. Addressing this issue from the perspective of the real-time systems community, this paper considers time-critical big-data. It deals with the definition of a time-critical big-data system from the point of view of requirements, analyzing the specific characteristics of some popular big-data applications. This analysis is complemented by the challenges stemmed from the infrastructures that support the applications, proposing an architecture and offering initial performance patterns that connect application costs with infrastructure performance.

SUMMARY During the last decade, the number of distributed application domains with temporal requirements has significantly augmented, arising the necessity of exploring new concepts and paradigms that allow, on the one hand, the development of dynamic and flexible distributed applications and, on the other hand, the reusability of code. Service‐oriented paradigms have been successfully applied to distributed environments, increasing their flexibility and allowing the reusability of their components. Besides, distributed real‐time Java technologies have shown to be a good candidate to deploy real‐time distributed applications. This paper presents a model for service‐oriented applications on a time‐triggered distributed real‐time Java environment, focusing on the definition of the temporal model of an application and its schedulability, applying and evaluating this model in real‐time service‐oriented composition algorithms. Copyright © 2012 John Wiley & Sons, Ltd.

There is a trend in industrial systems towards the use of common-off-the-shelf (COTS) components to develop applications that interact with open systems. This trend includes among others the use of high-level languages, such as Java, and Internet protocols (HTTP and Web Services). Although many industrial systems use these technologies at their business layers, they are far from offering a homogeneous programming platform in their most internal infrastructures. This paper extends the current practice by introducing a real-time Java-centric architecture for industrial systems. The architecture integrates existing and upcoming technology to define a Java-based approach. The empirical evidence, included in the paper, illustrates the performance of the core of the industrial layer of this architecture.

More and more industrial infrastructures consider the use of industrial wireless sensor network (IWSN) technology to perform control activities in industry. The benefits stemmed from IWSNs include flexible access (no wires are required) to elements that may interact with the factory floor. However, this support introduces new challenges: muling the almost permanent connectivity given by wired infrastructures is no longer available in IWSNs. To address this challenge, this paper explores data muling as the ability of transferring data between different elements within an industrial infrastructure. The proposed data-muling protocol uses a dual discovery and update (D&U) strategy. The prototype evaluation carried out on 6LowPan over IEEE 802.15.4 motes provides some insights on the performance that this type of infrastructure may offer within an industrial context. This paper also offers an extensive benchmark that may be used to test bounds and limitations of the proposed D&U protocol on the industrial use-cases.

Current approaches towards distributed real-time Java are mainly based on the idea of having user-defined remote objects, allocated in servers that may be invoked from clients. This article extends this support included in real-time Java with an extension called Remote Memory Areas (RMAs). RMAs offer a method that allows running user-defined code in a generic server that may be reused by several applications (i.e., it does not require defining one type of remote sever per application). The paper describes the abstraction, which is backward compatible with main approaches in distributed real-time Java, and provides empirical evidence on its performance on a use-case application.

As new technology becomes available, systems increase in complexity, which in turn, raises the expectations of users for new applications that may presumably be more complex. This spiral process requires the usage of appropriate techniques to control complexity such as decoupled design and development paradigms, and communications middleware that facilitate the development of distributed applications. The highest exponent of them is, currently, DDS middleware (Data Distribution System for Distributed Real-Time Systems) that is specifically designed for applications that have timing requirements. Also, virtualization techniques follow the principle of complexity reduction, and they allow to customize the offered computational platforms and to achieve server consolidation in different domains ranging from industrial control systems, distributed surveillance, or enterprise resource planning applications. This paper describes some considerations for merging real-time middleware, such as DDS, and virtualization technology with the aim of suiting the cyber physical domain. This virtual integration tries to bypass the typical bottlenecks of performance. Performance results track the differences between the executions of DDS middleware in the bare machine compared to a virtualized environment.

SUMMARY OSGi was designed with embedded systems in mind, its current support is insufficient for coping with one main characteristic of many embedded systems: real‐time performance. This article analyzes different key issues in providing OSGi with real‐time Java performance covering motivational issues, and different integration ways and challenges stemming from the integration. It also contributes a general framework for introducing real‐time performance in OSGi, which is called the real‐time for OSGi framework. The framework uses real‐time Java virtual machines and the real‐time specification for Java. The adoption of this framework allows cyber‐physical systems to experience real‐time Java performance in their applications. The framework introduces several integration levels for OSGi and real‐time specification for Java, and specific real‐time OSGi services. An empirical implementation was carried out using standard software, which was extended with the new defined services. Copyright © 2012 John Wiley & Sons, Ltd.

Communication middleware technologies are powerful instruments to develop and deploy remote laboratories for students to practice the control of real application cases. Middleware allows the rapid development and deployment of actual distributed settings since it abstracts the specifics of the different hardware platforms and communication media involved in the access of students to the lab material. This paper describes the practical settings carried out in the a case of a successful laboratory experience that allows students to simulate the on-line monitoring and control of remote systems, i.e., the train traffic in a simulated metro system. The innovative contribution of this experiment is the usage of data-centric middleware based on the publish/subscribe paradigm that has real-time properties. Up to our knowledge, such deployment with this particular middleware type has not been done, and it has given rise to a flexible setting that grows with the contributions of students. We have validated the idea by gathering the feedback of students with respect to the operation of the assignment, showing that this motivates the students' learning and enrollment in the assignment.

Abstract The current RTSJ (Real‐Time Specification for Java) threading model is dualized: a programmer has to decide between the high predictability offered by the region‐based model and the flexibility offered by the garbage collection. So far, there is no unique type of thread which offers both the high predictability of a non‐heap thread and the flexibility of a real‐time thread in a single entity. Furthermore, this lack has a serious impact on the programmer who has to deal with new and sometimes non‐trivial to use mechanisms, such as specific queues of objects or new types of threads, in order to avoid the priority inversion caused by the garbage collector. In order to tackle the concern properly and provide an improved and more generalized programming model, the authors propose a simple extension to the current threading model namedRealtimeThread++, in an attempt to introduce more flexibility in the RTSJ concurrency model. The paper describes the extension from several points of view: (i) the programmer, identifying scenarios that may benefit from it significantly; (ii) the real‐time Java technology perspective, identifying changes required in the current real‐time virtual machine to support it; and (iii) the accumulated experience, relating empirical results obtained from a software prototype that supports the extension. Copyright © 2010 John Wiley & Sons, Ltd.

Abstract The proliferation of a new generation of distributed real‐time embedded systems (DRE) characterized by special restrictions on its storage capacities, its available computation time, and the messages they can send through the network suggests a comprehensive redesign of the current distribution infrastructure in order to tune its performance. In this changing panorama, the paper concerns one of the protocols, Java's Remote Method Protocol (JRMP), used nowadays to interconnect different nodes of a distributed Java system, and explores the cost of integrating an improved protocol‐level multiplexing strategy in the context of an end‐to‐end remote invocation. The new multiplexing strategy helps middleware manage more efficiently unscheduled invocations that appear at runtime generated from a certain client node, especially in cases where preallocation of resources or dimensioning for the worst‐case are techniques not plausible. To this end, the paper examines an alternative based on the definition of a new subprotocol, called ConnectionLess, which offers built‐in multiplexing facilities for distributed Java applications. The performance of the new subprotocol is compared against the three already defined by JRMP (namely SingleOp, Stream, and Multiplex), taking into consideration parameters such as memory consumed in the Java's virtual machine and end‐to‐end response times. Copyright © 2011 John Wiley & Sons, Ltd.

Abstract Service‐based approach has been successfully applied to distributed environments, modelling them as pieces of functionality that exchange information by means of messages in order to achieve a common goal. The advantages of this approach can be also be applied to distributed real‐time systems, increasing their flexibility and allowing the creation of new brand applications from existing services in the system. If this is an online process, then time‐bounded composition algorithms are needed to not jeopardize the performance of the whole system. Different composition algorithms are studied and proposed, two of them optimal and another two based on heuristics. This paper presents an analytical solution that selects, depending on the structure of the application and on the load of the whole system, the most suitable composition algorithm to be executed in order to obtain a composed application in bounded time. Copyright © 2011 John Wiley & Sons, Ltd.

SUMMARY Many real‐time systems use preemptive priority‐based scheduling in their internals to guarantee certain real‐time performance. This includes technologies that range from The Real‐Time Specification for Java (RTSJ) to middleware like Real‐Time Common Object Request Broker Architecture (RT‐CORBA), which offers additional models and policies that blend client and server information. This decision eases the integration of real‐time admission tests and dispatching policies in these types of infrastructures. In this paper, we analyze different trade‐offs that emerge from the definition of different propagation models for distributed real‐time Java. The paper covers technological integration aspects as impact on interfaces and other practical issues mainly related to the performance that this model offers to a real‐time application and non‐functional overhead. The contribution described in the paper may help in the development of The Distributed Specification for Java (DRTSJ). Copyright © 2011 John Wiley & Sons, Ltd.

More-and-more, the use of Java as a programming language for real-time applications is becoming of interest in industrial middleware. This is mainly because it offers advantages for the programmer as reduced deployment times, increased portability, and a number of APIs that may be integrated in large distributed applications. This paper contributes a dual communication model for distributed real-time Java applications. Current efforts in distributed real-time Java [e.g., The Distributed Real Time Specification for Java (DRTSJ)] are mainly focused on remote invocations (R.I.) and set aside other valuable approaches such as distributed events. The proposed model offers two choices for developing distributed real-time Java applications (one based on R.I., and another on distributed events), which may be used to develop applications. Both models include an additional support for asynchronism in communications, a feature that may speed up their communication performance. This paper includes a description for the two models, the changes that are required in the current API to accommodate them, and an empirical evaluation of their performance on a reference implementation.

Today's trend in real-time systems reveals the necessity of new technologies to easy their development and maintenance. Among others, some interesting alternatives are found in high-level real-time programming languages, better development models, or simple architectures and models. From the perspective of real-time Java, a recent real-time programming language, this paper offers an architecture (and its corresponding Java interfaces) to help the development of an upcoming distributed real-time technology for Java (named DRTSJ). To that end it describes a neutral architecture based on Java's Remote Method Invocation (RMI) and The Real-time Specification for Java (RTSJ). The empirical evidences included in the paper offer also interesting clues on the performance this technology may deliver.

The increasing complexity of networked embedded systems (NES) brings in the vision of large-scale systems made of subparts with decoupled interaction. In highly decoupled environments, it is required to introduce software paradigms that adjust well to this degree of independence among subsystems. In modern NES, real-time properties and reconfiguration facilities are not only an added value but an unavoidable trend that research is currently focusing at. Service-oriented architectures (SOA) are an easy-to-understand natural means to provide such decoupled model of operation; service-based applications are made of a set of self-contained pieces of functionality (services) that cooperate by exchanging messages to provide the application's common goal. This paper presents a middleware architecture that includes real-time support for service-oriented NES. The architecture includes the fundamental set of functions to support timely service-based composition and execution. The architecture is the core part of the iLAND project that aims at supporting deterministic service-based composition and reconfiguration in service-based NES. The architecture can be built on top standard communication middleware cores (as DDS or RT-CORBA), since it supports synchronous and asynchronous communication models. An experimental set up for real-time video transmission has been developed to validate it.

Many real-time systems use preemptive priorities in their internals to guarantee certain real-time performance. This includes technologies that range from RTSJ (The Real-Time Specification for Java) to middleware like Real-Time CORBA (Common Object Request Broker Architecture) which offers additional models and policies that blend client and server information. This decision makes easier the integration of real-time acceptance tests and dispatching policies in these kinds of infrastructures. In this paper, we analyze different tradeoffs that emerge from the definition of different propagation models for distributed real-time Java. The paper covers technological integration aspects, impact on interfaces, and other practical issues more related to the performance that this model offers to a real-time application

This article presents an approach to providing real-time support for Java's Remote Method Invocation (RMI) and its integration with the RTSJ memory model in order to leave out garbage collection. A new construct for remote objects, called No-heap Remote object ( NhRo ), is introduced. The use of a NhRo guarantees that memory required to perform a remote invocation (at the server side) does not use heap memory. Thus, the aim is to avoid garbage collection in the remote invocation process, improving predictability and memory isolation of distributed Java-based real-time applications. The article presents the bare model and the main programming patterns that are associated with the NhRo model. Sun RMI implementation has been modified to integrate the NhRo model in both static and dynamic environments.

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.

More and more, the use of real-time distribution middlewares programmed with high-level languages like Java is becoming of interest for industrial systems because this type of infrastructures reduce development efforts required to both design and maintain complex networked applications. In that way towards having better development tools, this paper deals with the very specific issue of the asynchronism from the particular perspective of Java's distributed technologies. It proposes and evaluates an extension to the Java's remote method invocation (RMI) with additional support for asynchronous remote invocations. Such a mechanism makes the transmission of some messages, typically those that do not require any confirmation from the server, much more efficient than synchronous communications, and consequently they optimize and speed up the performance of many industrial networked applications. In more detail, this paper concerns with the model itself and the set of changes it requires within their middleware programming interfaces and inside communication protocols to accommodate the proposed model. The proposal is supported by empirical evidences from a prototype developed as partial proof-of-concept.

This paper presents a model for quality-of-service (QoS)-aware service composition in distributed systems with real-time and fault-tolerance requirements. This model can be applied in application domains like, for example, remote monitoring, control and surveillance. Classic approaches to real-time systems do not provide the flexibility and fault-tolerance required in new emerging environments that need to combine a high degree of dynamism with temporal predictability. Our approach addresses these new challenges by combining concepts from the service oriented paradigm and distributed real-time systems. We propose a concrete system model based on a holistic time-triggered-based approach for design and configuration. Based on this model, we propose two algorithms for the composition of QoS-aware service-based applications with temporal requirements: an exhaustive algorithm that computes the optimal service combination in terms of a figure of merit, suitable for offline composition; and an improved algorithm based on heuristics and partial figures of merit, suitable for online composition. Experimental results show that the latter reduces dramatically the number of combinations explored with a minimal degradation in the quality of the solution, making it feasible for online execution in dynamic environments.

Current RTSJ (The Real-Time Specification for Java) threading model is dualized: programmers have to decide between the high predictability offered by its region-based model and the flexibility offered by its garbage-collected model. Up to now, there is not a unique type of thread that offers, in a single entity, the highest predictability, and flexibility together. This lack has serious consequences on the programmer who has to deal with new and sometimes non-trivial mechanisms, such as queues of objects or the No-heap Real-Time Threads, to avoid the priority inversion caused by the garbage collector. In order to tackle these issues and provide an improved and more generalized programming model, the authors propose an extension to the current threading model that unifies the RTSJ threading model: the RealtimeThread++ extension.

Recently, the application domains where the development of systems with temporal guarantees is needed have increased. The majority of such domains are dynamic environments where the classical design approach is no longer applicable since it is too pessimistic. Thus, new challenges arise to adapt the current methodologies used in different architectural levels to these new environments. New directions and paradigms are needed to allow combining functional flexibility and dynamism with temporal predictability. The current work addresses these new challenges through the exploration of the applicability of concepts from the service oriented paradigm to distributed real-time systems. We propose a concrete system model based on a holistic time-triggered-based approach for design and configuration. Based on this model, we analyse the architectural entities required for two different architectural design approaches: static, when no reconfigurations at run-time are admitted, and dynamic, when these reconfigurations are possible. An exhaustive composition algorithm is also proposed.

Recently, new trends in application development for distributed platforms, such as the composable services model, attempt to provide more flexibility in system design, deployment and execution. Such trends, and particularly the referred composable services model, can also be beneficial in real-time distributed embedded systems, also providing a means to support more adaptive behaviors, reacting to the execution environment or coping with system reconfiguration. This paper explores a relatively new direction, which is the extension of the service-based model to dynamic, i.e. at run-time, composition in real-time distributed environments, in order to support the level of flexibility and adaptibility referred above. The paper proposes an architecture to support such dynamic service composition that is based on the flexible time triggered communication paradigm (FTT).To achieve the desired goal, we also redefine the concepts of service and service-based application in the concept of the FTT paradigm. Finally, we show experimental results obtained with a prototype implementation of the proposed architecture that confirm its feasibility and good temporal behavior

This paper describes an approach towards the definition and implementation of a synchronization service on top of a remote object model offered by an unicast real-time remote object paradigm. Also an architecture model based on the RTSJ (real-time specification for Java) and the distribution middleware RMI (remote method invocation) specifications is proposed in order to give support to the model, defining a convergence layer that manages the underlying resources involved in a master-slave communication through a new API. Finally, preliminary results from an implementation prototype show the feasibility of the model and provide an initial estimation of jitters and the performance of the synchronization service

This paper presents a memory management solution for distributed real-time Java. The proposed model is targeted at distributed applications that require to keep their internal state and that consume a bounded memory size in their operation. The aim is to provide an alternative to the garbage collector for distributed real-time systems and to avoid the penalties it introduces. The approach is based on the usage of scoped memory defined in the real-time specification for Java (RTSJ). Our solution introduces constraints in the programming model and in the current distributed Java architecture. However, these are compensated by eliminating the dependency of the garbage collector in the end-to-end invocation and by achieving self-cleaning with respect to the memory consumed by remote invocations.