Anastasio Molano

The denodo data integration platform

The world today is characterised by the proliferation of information sources available through media such as the WWW, databases, semi-structured files (e.g. XML documents), etc. Nevertheless, this information is usually scattered, heterogeneous and weakly structured, so it is difficult to process it automatically. DENODO Corporation has developed a mediator system for the construction of semi-structured and structured data integration applications. This system has already been used in the construction of several applications on the Internet and in corporate environments, which are currently deployed at several important Internet audience sites and large sized business corporations. In this extended abstract, we present an overview of the system and we put forward some conclusions arising from our experience in building real-world data integration applications, focusing in some challenges we believe require more attention from the research community.

Integrating Data Sources and Network Analysis Tools to Support the Fight Against Organized Crime

We discuss how methods from social network analysis could be combined with methodologies from database mediator technology and information fusion in order to give police and other civil security decision-makers the ability to achieve predictive situation awareness. Techniques based on these ideas have been demonstrated in the EU PASR project HiTS/ISAC.

Real-time multimedia systems

The expansion of multimedia networks and systems depends on real-time support for media streams and interactive multimedia services. Multimedia data are essentially continuous, heterogeneous, and isochronous, three characteristics with strong real-time implications when combined. At the same time, some multimedia services, like video-on-demand or distributed simulation, are real-time applications with sophisticated temporal functionalities in their user interface. We analyze the main problems in building such real-time multimedia systems, and we discuss-under an architectural prospect-some technological solutions especially those regarding determinism and efficient synchronization in the storage, processing, and communication of audio and video data.<<ETX>>

Mediator systems in E-commerce applications

The world today is characterised by the proliferation of information sources available through media such as the WWW, databases, semi-structured files, etc. But, very often, this information is scattered, heterogeneous and weakly structured (semi-structured data). E-commerce is, by nature, one field in which this phenomena is specially strong. This paper overviews a mediator system for the construction of structured and semi-structured data integration applications. This system has been used in the construction of various applications on the Internet and in corporate environments, which are being used in real operational environments. Some conclusions arising from the experience gained from the use of such applications are also put forward.

The design and implementation of a multimedia storage server to support video-on-demand applications

In this paper we present the design and implementation of a client/server based multimedia architecture for supporting video-on-demand applications. We describe in detail the software architecture of the implementation along with the adopted buffering mechanism. The proposed multithreaded architecture obtains, on one hand, a high degree of parallelism at the server side, allowing both the disk controller and the network card controller work in parallel. On the other hand; at the client side, it achieves the synchronized playback of the video stream at its precise rate, decoupling this process from the reception of data through the network. Additionally, we have derived, under an engineering perspective, some services that a real-time operating system should offer to satisfy the requirements found in video-on-demand applications.

GEODAS: an industrial experience with component frameworks for data acquisition and analysis systems

Data acquisition and analysis systems (DAAS) are hardware/software systems with a strong dependence on the features of the process under control, where the amount of data and the sampling frequency of signals to be processed are the main critical aspects of the system. Nowadays DAAS applications are designed according to the specific needs of each particular field. These solutions produce ad hoc software developments, very difficult to reuse. Nevertheless, the basic structure of DAAS is the same across all the different application fields. GEODAS is an EU-funded project whose goal is to develop a framework of reusable, generic components focused on the high-performance DAAS domain. These components capture the generic behaviour of data acquisition systems and offer a new approach for the creation of these systems, which is more modular, reusable, independent from the electronics interface and more platform independent. This paper describes the application of component-based software engineering concepts in an industrial, high-performance, real-time application domain.

A preemptive priority-based disk I/O subsystem for the management of hard real-time disk traffic

We present the design and implementation of a disk I/O subsystem appropriated for the management of hard real time disk traffic. The proposed disk I/O subsystem allows the invocation of preemptive priority based disk I/O operations, both for non contiguous and contiguous data layouts. Disk I/O requests are scheduled in a common layer upon the disk driver, where access to the disk is enforced by either giving control or blocking invoking threads according to the selected scheduling policy (Rate Monotonic or EDF). The highest priority thread is granted access to the disk and it makes use of the full disk bandwidth, enforcing preemption whenever a higher priority request is demanding service. Preemptibility in non contiguously allocated files is achieved with a granularity that equals the time to read/ write a file system block. Additionally, a splitting up mechanism, that splits disk I/O requests into smaller ones, improves preemptibility in contiguously allocated files. Besides the description of the implementation we include a comprehensive performance evaluation. We have also identified the particular conditions under which a set of requests is schedulable in a predictable fashion using the proposed disk I/O subsystem.

Operating system support for the management of hard real-time disk traffic

Abstract Emerging applications like C3I systems, real-time databases, data acquisition systems and multimedia servers require access to secondary storage devices under timing constraints. In this paper, we focus on operating system support needed for managing real-time disk traffic with hard deadlines. We present the design and implementation of a preemptive deadline-driven disk I/O subsystem suitable for real-time disk traffic management. Preemptibility is achieved with a granularity that is automatically controlled by the I/O subsystem according to current workload and filesystem data layout. An admission control test checks the current resource availability for a given workload. We show that contiguous layout is necessary to maintain hard real-time guarantees and a reasonable level of disk throughput. Finally, we show how buffering can be used to obtain utilization factors close to the maximum disk bandwidth possible.

Minimizing buffer requirements in video-on-demand servers

Memory management is a key issue when designing cost effective video on demand servers. State of the art techniques, like double buffering, allocate buffers in a per stream basis and require huge amounts of memory. We propose a buffering policy, namely Single Pair of Buffers, that dramatically reduces server memory requirements by reserving a pair of buffers per storage device. By considering in detail disk and network interaction, we have also identified the particular conditions under which this policy can be successfully applied to engineer video on demand servers. Reduction factors of two orders of magnitude compared to the double buffering approach can be obtained. Current disk and network parameters make this technique feasible.