A qualitative human-centric evaluation of flexibility in middleware implementations

Today middleware is much more powerful, more reliable and faster than it used to be. Nevertheless, for the application developer, the complexity of using middleware platforms has increased accordingly. The volume and variety of application contexts that current middleware technologies have to support require that developers be able to anticipate the widest possible range of execution environments, desired and undesired effects of different programming strategies, handling procedures for runtime errors, and so on. This paper shows how a generic framework designed to evaluate the usability of notations (the Cognitive Dimensions of Notations Framework, or CDN) has been instantiated and used to analyze the cognitive challenges involved in adapting middleware platforms. This human-centric perspective allowed us to achieve novel results compared to existing middleware evaluation research, typically centered around system performance metrics. The focus of our study is on the process of adapting middleware implementations, rather than in the end product of this activity. Our main contributions are twofold. First, we describe a qualitative CDN-based method to analyze the cognitive effort made by programmers while adapting middleware implementations. And second, we show how two platforms designed for flexibility have been compared, suggesting that certain programming language design features might be particularly helpful for developers.     

FamiWare: a family of event-based middleware for ambient intelligence

Most of the middlewares currently available focus on one type of device (e.g., TinyOS sensors) and/or are designed with one requirement in mind (e.g., data management). This is an important limitation since most of the AmI applications work with several devices (such as sensors, smartphones or PDAs) and use a high diversity of low-level services. Ideally, the middleware should provide a single interface for accessing all those services able to work in heterogeneous devices. To address this issue, we propose a family of configurable middleware (FamiWare) with a really flexible architecture, instead of building a single version of a middleware with a rigid structure. In this work, we present the architecture of our middleware that can be configured, following a Software Product Line approach, in order to be instantiated in a particular device fulfilling specific application requirements. Furthermore, we evaluate that the decisions taken at architecture and implementation are the adequate ones for this kind of constrained devices.     

EgoSpaces: facilitating rapid development of context-aware mobile applications

Today's mobile applications require constant adaptation to their changing environments, or contexts. Technological advances have increased the pervasiveness of mobile computing devices such as laptops, handhelds, and embedded sensors. The sheer amount of context information available for adaptation places a heightened burden on application developers as they must manage and utilize vast amounts of data from diverse sources. Facilitating programming in this data-rich environment requires a middleware that provides context information to applications in an abstract form. In this paper, we demonstrate the feasibility of such a middleware that allows programmers to focus on high-level interactions among programs and to employ declarative abstract context specifications in settings that exhibit transient interactions with opportunistically encountered components. We also discuss the novel context-aware abstractions the middleware provides and the programming knowledge necessary to write applications using it. Finally, we provide examples demonstrating the infrastructure's ability to support differing tasks from a wide variety of application domains.     

Taking an object-centric view on dynamic information with object flow analysis

A large body of research analyzes the runtime execution of a system to extract abstract behavioral views. Those approaches primarily analyze control flow by tracing method execution events or they analyze object graphs of heap memory snapshots. However, they do not capture how objects are passed through the system at runtime. We refer to the exchange of objects as the object flow, and we claim that it is necessary to analyze object flows if we are to understand the runtime of an object-oriented application. We propose and detail object flow analysis, a novel dynamic analysis technique that takes this new information into account. To evaluate its usefulness, we present a visual approach that allows a developer to study classes and components in terms of how they exchange objects at runtime. We illustrate our approach on three case studies.     

Mobile data collection in sensor networks: The TinyLime middleware

In this paper we describe TinyLime, a novel middleware for wireless sensor networks that departs from the traditional setting where sensor data is collected by a central monitoring station, and enables instead multiple mobile monitoring stations to access the sensors in their proximity and share the collected data through wireless links. This intrinsically context-aware setting is demanded by applications where the sensors are sparse and possibly isolated, and where on-site, location-dependent data collection is required. An extension of the Lime middleware for mobile ad hoc networks, TinyLime makes sensor data available through a tuple space interface, providing the illusion of shared memory between applications and sensors. Data aggregation capabilities and a power-savvy architecture complete the middleware features. The paper presents the model and application programming interface of TinyLime, together with its implementation for the Crossbow MICA2 sensor platform.     

SchedSP: a Grid‐based application service provider of scheduling solutions

In this paper, SchedSP, a middleware framework for providing scheduling solutions as services over the Internet, is presented. Emphasis is given on creating a reusable framework that facilitates the development of specialized clients for the input, output and control interfaces of the various scheduling applications. SchedSP manages the task of preparing and running the required processes and allows the application interface developer to focus on the functionality and efficiency of the interface. The Internet‐based scheduling applications created are competitive in all aspects with traditional locally executed applications. In this paper, detailed architecture and implementation details of the SchedSP framework prototype are presented. In addition, the methodology for creating specific case studies based on the SchedSP middleware framework is presented. Copyright © 2005 John Wiley & Sons, Ltd.     

Combining heterogeneous service technologies for building an Internet of Things middleware

Radio-frequency identification (RFID) is a technology that allows ordinary objects to be uniquely identified by “smart tags” which are also capable of storing small quantities of data. The term Internet of Things was originated from a vision strongly coupled with supply-chain concerns and RFID tagged objects. However the idea of such Internet of Things has evolved in a wider sense, referring now to a ubiquitous object society combining RFID, sensor networks and pervasive computing technologies. This scenario involves different requirements such as heterogeneity and dynamicity of objects, sensors, applications and protocols as well as the need for allowing the dynamic evolution of such applications. These issues seemed to be easily addressed if the principles of service-oriented computing (SOC), like loose coupling and heterogeneity, are used for constructing such architectures and applications. In this paper we underline what benefits SOC can offer to constructing a middleware for the Internet of Things. These concepts have been applied in a service-oriented middleware that tries to leverage the existing Internet of Things architectural concepts by using SOC principles in order to bring more flexibility and dynamicity. We describe the approaches used in that middleware and the lessons learned from that experience. This middleware was initially tested on an application for tracking and monitoring supply-chain objects, and later extended to target wider application domains that are also described in this paper. The project described here has become part of the OW2 AspireRFID open-source project.     

Providing user context for mobile and social networking applications

The processing capabilities of mobile devices coupled with portable and wearable sensors provide the basis for new context-aware services and applications tailored to the user environment and daily activities. In this article, we describe the approach developed within the UPCASE project, which makes use of sensors available in the mobile device as well as sensors externally connected via Bluetooth to provide user contexts. We describe the system architecture from sensor data acquisition to feature extraction, context inference and the publication of context information in web-centered servers that support well-known social networking services. In the current prototype, context inference is based on decision trees to learn and to identify contexts dynamically at run-time, but the middleware allows the integration of different inference engines if necessary. Experimental results in a real-world setting suggest that the proposed solution is a promising approach to provide user context to local mobile applications as well as to network-level applications such as social networking services.     

Utilizing architectural styles to enhance the adaptation support of middleware platforms

ContextModern middleware platforms provide the applications deployed on top of them with facilities for their adaptation. However, the level of adaptation support provided by the state-of-the-art middleware solutions is often limited to dynamically loading and off-loading of software components. Therefore, it is left to the application developers to handle the details of change such that the system’s consistency is not jeopardized.ObjectiveWe aim to change the status quo by providing the middleware facilities necessary to ensure the consistency of software after adaptation. We would like these facilities to be reusable across different applications, such that the middleware can streamline the process of achieving safe adaptation.MethodOur approach addresses the current shortcomings by utilizing the information encoded in a software system’s architectural style. This information drives the development of reusable adaptation patterns. The patterns specify both the exact sequence of changes and the time at which those changes need to occur. We use the patterns to provide advanced adaptation support on top of an existing architectural middleware platform.ResultsOur experience shows the feasibility of deriving detailed adaptation patterns for several architectural styles. Applying the middleware to adapt two real-world software systems shows the approach is effective in consistently adapting these systems without jeopardizing their consistency.ConclusionWe conclude the approach is effective in alleviating the application developers from the responsibility of managing the adaptation process at the application-level. Moreover, we believe this study provides the foundation for changing the way adaptation support is realized in middleware solutions.     

MidFusion: An adaptive middleware for information fusion in sensor network applications

Applications and services are increasingly dependent on networks of smart sensors embedded in the environment to constantly sense and react to events. In a typical sensor network application, information is collected from a large number of distributed and heterogeneous sensor nodes. Information fusion in such applications is a challenging research issue due to the dynamicity, heterogeneity, and resource limitations of sensor networks. We present MidFusion, an adaptive middleware architecture to facilitate information fusion in sensor network applications. MidFusion discovers and selects the best set of sensors or sensor agents on behalf of applications (transparently), depending on the quality of service (QoS) guarantees and the cost of information acquisition. We also provide the theoretical foundation for MidFusion to select the best set of sensors using the principles of Bayesian and Decision theories. A sensor selection algorithm (SSA) for selecting the best set of sensors is presented in this paper. Our theoretical findings are validated through simulation of the SSA algorithm on an example scenario.     

Dynamic load‐balancing mechanism for distributed Java applications

Program environments or operating systems generally leave the decision on the allocation of program entities to the developer, offering either placement directives, or tools available through the manipulation of a graphical interface. These approaches cannot always take into account the dynamic behavior of applications, dynamicity in the execution environment or the heterogeneity of the execution platform. Transparent deployment algorithms are necessary for automizing and optimizing application distribution. The Adaptive Distributed Applications in Java (ADAJ) project deals with placement and migration of Java objects. It automatically deploys parallel Java applications on a cluster of workstations using monitoring information about the application behavior. The transparency obtained through the integration of these tools in the middleware makes such an environment easy to use and improves efficiency. Copyright © 2005 John Wiley & Sons, Ltd.     

Remote Collaboration Over Video Data: Towards Real-Time e-Social Science

The design of distributed systems to support collaboration among groups of scientists raises new networking challenges that grid middleware developers are addressing. This field of development work, ‘e-Science’, is increasingly recognising the critical need of understanding the ordinary day-to-day work of doing research to inform design. We have investigated one particular area of collaborative social scientific work – the analysis of video data. Based on interviews and observational studies, we discuss current practices of social scientific work with digital video in three areas: Preparation for collaboration; Control of data and application; and Annotation configurations and techniques. For each, we describe how these requirements feature in our design of a distributed video analysis system as part of the MiMeG project: our security policy and distribution; the design of the control system; and providing freeform annotation over data. Finally, we review our design in light of initial use of the software between project partners; and discuss how we might transform the spatial configuration of the system to support annotation behaviour.     

Fault tolerant Web Services

Zwass suggested that middleware and message service is one of the five fundamental technologies used to realize Electronic Commerce (EC). The Simple Object Access Protocol (SOAP) is recognized as a more promising middleware for EC applications among other leading candidates such as CORBA. Many recent polls reveal however that security and reliability issues are major concerns that discourage people from engaging in EC transactions. We notice that the fault-tolerance issue is somewhat neglected in the current standard, i.e., SOAP 1.2. We therefore propose a fault tolerant Web Services called fault tolerant SOAP or FT-SOAP through which Web Services can be built with higher resilience to failure. FT-SOAP is based on our previous experience with an object fault tolerant service (OFS) and OMG’s fault tolerant CORBA (FT-CORBA). There are many architectural differences between SOAP and CORBA. One of the major contributions of this work is to discuss the impact of these architectural differences on FT-SOAP design. Our experience shows that Web Services built on a SOAP framework enjoy higher flexibility compared to those built on CORBA. We also point out the limitations of the current feature sets of SOAP 1.2, e.g. the application of the intermediary. In addition, we examine two implementation approaches; namely, one based on the SOAP 1.2’s intermediary, and the other on Axis handler. We conclude that the intermediary approach is infeasible due to the backward compatibility issue. We believe our experience is valuable not only to the fault-tolerance community, but also to other communities as well, in particular, to those who are familiar with the CORBA platform.     

StarBus+: Distributed Object Middleware Practice for Internet Computing

In the past decade, the booming of Internet challenges the middleware in three aspects: quality of service, balance of changes and stabilization, and across-Internet integration. This paper presents our work on distributed object computing middleware technology for these challenges, as well as the research and development on StarBus , which is a CORBA standard-compliant middleware suite with the features such as object request broker supporting multi-* quality of service, component model, and integration with Web Service. This paper comprehensively presents the design and characteristics of StarBus , and demonstrates how StarBus is enhanced to address the challenges of Internet computing through three case studies: inter-enterprise integration over Internet, application evolution through dynamic reconfiguration, and great massive information system building. The paper also suggests some research directions which are important for Internet computing.     

A reflective service gateway for integrating evolvable sensor–actuator networks with pervasive infrastructure

As sensor and actuator networks (SANETs) evolve, sensor and actuator nodes (SANs) will be frequently added, removed, and upgraded as needed, which we call evolvable SANETs (ESANETs). However, existing service gateways for SANETs are assumed to know the operational environment at design time with limited awareness of operational SANET conditions and, in the meanwhile, provide a single particular form of access without knowledge of application activities. Therefore, current service gateways are infeasible to accommodate ESANETs. To cope with this, this paper presents a reflective service gateway (RSG), which self-adapts to ESANET changes and enables ESANETs to customize its activities according to the application services involved. The key to enabling this is a reflection mechanism whereby RSG is able to monitor network status of multi-hop ESANETs so that its internal structures and behaviors can be altered adaptively. In addition, RSG allows heterogeneous middleware systems (HMSs) to concurrently access ESANETs, promoting the flexibility of RSG to be integrated with HMSs. To evaluate RSG, we compare the ESANET messaging cost of RSG with that of the OSGi-based framework by mathematical models. In addition, we implement a RSG prototype and a set of middleware system case studies. Finally, we conduct empirical performance measurements with home sensor and actuator applications using ZigBee.     

An Adaptive Middleware for Context-Sensitive Communications for Real-Time Applications in Ubiquitous Computing Environments

Context-sensitivity is an important expected capability in applications in ubiquitous computing (ubicomp) environments. These applications need to use different contextual information from the user, host device, on board sensors, network, and the ambient environments to systematically adapt their actions. In addition, some context-sensitive applications may use specific contextual conditions to trigger impromptu and possibly short-lived interactions with applications in other devices. This property, referred to as context-sensitive or context-aware communications, allows applications to form short-range mobile ad hoc networks consisting of mobile and stationary devices, sensors, and other computing resources. Real-time applications, especially those having reactive behavior, running on embedded devices and requiring context-sensitive communications support, pose new challenges related to systematic representation of specific contexts, associations of contexts with real-time actions, timely context data collection and propagation, and transparent context-sensitive connection establishment. An object-based middleware can be effective to meet these challenges if such a middleware can provide a well-defined development framework as well as lightweight runtime services. In this paper, an adaptive and object-based middleware, called reconfigurable context-sensitive middleware (RCSM) is presented to facilitate context-sensitive communications in ubicomp environments. To facilitates context-sensitive communications, RCSM provides a context-aware interface definition language for specifying context-sensitive interfaces of real-time objects, an object container framework for generating interfaces-specific context-analyzers, and a context-sensitive object request broker for context-sensitive object discovery and impromptu connection management. RCSM is adaptive in the sense that depending on the context-sensitive behavior of the applications, it adapts its object discovery and connection management mechanisms.     

An energy-efficient object discovery protocol for context-sensitive middleware for ubiquitous computing

Many ubiquitous computing applications may be context-sensitive due to the ambient environments, mobile devices, and other detectable factors. A context-sensitive middleware provides the necessary support to context-sensitive application objects to participate in spontaneous and ad hoc communications with other applications in remote devices whenever suitable contexts exist. A context-sensitive middleware can provide this support effectively if its communication subsystem, such as an Object Request Broker (ORB), can properly discover other objects in devices. This capability is usually known as object discovery protocol. An energy-efficient object discovery protocol is needed to help prolong a device's battery life because many devices in ubiquitous computing environments are battery-powered and, thus, have limited energy sources. An energy-efficient object discovery protocol, RKS, for context-sensitive middleware for ubiquitous computing is presented. RKS reduces energy consumption by reducing the amount of information that needs to be sent to remote devices to discover objects. A novel feature of RKS is that it advertises its server-objects' availability only when it detects that these servers can be activated in the current context and when it finds that the neighbor devices have some potential clients that are willing to discover objects. Analytical comparisons of the energy-consumptions are given between RKS and two other protocols for object discovery in context-sensitive middleware. Furthermore, our experimental results, based on the implementations of these protocols and RKS on a context-sensitive middleware test bed, confirm our analytical results in that the RKS conserves more energy than the other two.     

An adaptive middleware framework for context-aware applications

We describe a middleware framework for the adaptive delivery of context information to context-aware applications. The framework abstracts the applications from the sensors that provide context. Further applications define utility functions on the quality of context attributes that describe the context providers. Then, given multiple alternatives for providing the same type of context, the middleware applies the utility function to each alternative and choose the one with maximum utility. By allowing applications to delegate the selection of context source to the middleware, our middleware can implement autonomic properties, such as self-configuration when new context providers appear and resilience to failures of context providers.

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Robot Head Motion Control with an Emphasis on Realism of Neck–Eye Coordination during Object Tracking

Important aspects of present-day humanoid robot research is to make such robots look realistic and human-like, both in appearance, as well as in motion and mannerism. In this paper, we focus our study on advanced control leading to realistic motion coordination for a humanoid’s robot neck and eyes while tracking an object. The motivating application for such controls is conversational robotics, in which a robot head “actor” should be able to detect and make eye contact with a human subject. Therefore, in such a scenario, the 3D position and orientation of an object of interest in space should be tracked by the redundant head–eye mechanism partly through its neck, and partly through its eyes. In this paper, we propose an optimization approach, combined with a real-time visual feedback to generate the realistic robot motion and robustify it. We also offer experimental results showing that the neck–eye motion obtained from the proposed algorithm is realistic comparing to the head–eye motion of humans.