We present a transactional and concurrent replication scheme that is designed for hybrid data store architectures. The system design and the requirements are motivated by the real business cases we encountered during the development of our commercial database product. We consider two databases where the original database handles read/write transactional application workloads while the second database handles read-only workloads from the same applications over the data periodically replicated from the original database. The main requirement is ensuring the application of the updates on the replica database in the exact same order they were executed in the original database, which is called executiondefined order. Although this requirement could easily be satisfied by the serial execution of the updates in the commit order, doing so in an ecient manner by exploiting concurrency is a challenging problem. We present a novel concurrency control algorithm to addresses that problem by also allowing the read-only workloads on the replica database to interleave with the concurrent replication. The extensive experiments show the ecacy of the proposed solution.

In this paper, we propose a content-based publish/subscribe (pub/sub) framework that delivers matching content to subscribers in their desired format. Such a framework enables the pub/sub system to accommodate richer content formats including multimedia publications with image and video content. In our proposed framework, users (consumers) in addition to specifying their information needs (subscription queries), also specify their profile which includes the information about their receiving context which includes characteristics of the device used to receive the content (e.g., resolution of a PDA used by a consumer). The pub/sub system besides being responsible for matching and routing the published content, also becomes responsible for converting the content into the suitable format for each user. Content conversion is achieved through a set of content adaptation operators (e.g., image transcoder, document translator, etc.). We study algorithms for placement of such operators in heterogeneous pub/sub broker overlay in order to minimize the communication and computation resource consumption. Our experimental results show that careful placement of operators in pub/sub overlay network results in significant cost reduction.

We present a data management platform in the cloud, CloudDB. The guiding principle of CloudDB’s design is establishing data independence for the applications that need to use diverse underlying data stores that are optimized for varying workload needs and characteristics. The applications should not have to be aware of the physical organization of the data and how the data is accessed. Ideally, an application only needs a logical specification of the data access layer and the data access requests are handled in a declarative way. CloudDB hosts variety of specialized databases that deliver high performance, scalability, and cost efficiency for varying application needs. CloudDB’s API layer is designed in such a way to give data independence to the higher level applications. The goal is to let the clients use just a simple, standard, and uniform language API to access data management functions as a service.

We present cluster-based publish/subscribe, a novel architecture that is not only resilient to event broker failures but also provides load balancing and fast event dissemination service. Our proposed approach achieves fault tolerance by organizing event brokers in clusters. Multiple inter-cluster links provide continuous availability of dissemination service in presence of broker failure without requiring subscription retransmission or reconstruction of broker overlay. Furthermore, the proposed architecture provides a fast event dissemination infrastructure that significantly reduces subscription and publication dissemination traffic and load on event brokers. Our experimental results show that even in the presence of failures in broker network, event dissemination is not interrupted and dissemination speed and load are significantly improved compared to the existing approached.

Surveillance is an important task for guaranteeing the security of individuals. Being able to intelligently monitor the activity in given spaces is essential to achieve such surveillance. Sentient spaces based on a large set of sensors provide the potential for such intelligent monitoring. However, heavily instrumenting a space with sensors it is not enough to build a sentient space. One needs a software architecture that allows programming all these sensors in a transparent and efficient manner. In this paper, we present SATware, a stream acquisition and transformation middleware we are developing to analyze, query, and transform multimodal sensor data streams to facilitate flexible development of sentient environments. SATware provides a powerful application development environment in which users (i.e., application builders) can focus on the specifics of the application without having to deal with the technical peculiarities of accessing a large number of diverse sensors via different protocols.

Real-time CORBA is a middleware standard that has demonstrated successes in developing distributed, realtime, and embedded (DRE) systems. Customizing real-time CORBA for an application can considerably reduce the size of the middleware and improve its performance. However, customizing middleware is an error-prone task and requires deep knowledge of the CORBA standard as well as the middleware design. This paper presents ZEN-kit, a graphical tool for customizing RTZen (an RTSJ-based implementation of real-time CORBA). This customization is achieved through modularizing the middleware so that features may be inserted or removed based on the DRE application requirements. This paper presents three main contributions: 1) it describes how real-time CORBA features can be modularized and configured in RTZen using components and aspects, 2) it provides a configuration strategy to customize real-time middleware to achieve low-footprint ORBs, and 3) it presents ZEN-kit, a graphical tool for composing customized real-time middleware.