Santiago Pavón

State exploration by transformation with LOLA

LOTOS is a Formal Description Technique developed within ISO to specify services and protocols. This paper describes a tool for doing LOTOS to LOTOS transformations. It has applications in state exploration, deadlock detection, testing, validation and in design by stepwise refinement. The transformations are: expansion (transformation of parallelism into summation and prefix); parameterized expansion; i action removal. The transformations obtain LOTOS specifications which relate to the original one through strong (expansion and parameterized expansion) or weak (i-action removal) bisimulation congruence.

ISABEL: A CSCW Application for the Distribution of Events

Introduction Many activities which in the past have required physical presence and direct interaction among participants can be performed in a distributed fashion with the help of advanced information technologies such as, CSCW [1,2] (Computer Supported Cooperative Work), interactive multimedia services and broadband communications. Technologies aiming at supporting the collaboration among individuals or groups are identified under the term groupware technologies. Asynchronous interactions which do not require physical presence of interacting persons have matured during the last years. Very successful examples of asynchronous groupware exist. LOTUS Notes [3] is considered probably the most successful commercial product in this area. The Internet and many of its application can be considered as groupware technologies to some extend. Technology can support today also synchronous interaction where real time contact among individuals is required. We mean by synchronous interaction the exchange of verbal, visual, ... messages or information, like the exchanges of information carried out typicaly in meetings, conversations or other activities where several participants collaborate in physical presence. Remote synchronous interaction is not new, the plain old telephone is a very good example of an old technology supporting a simple but very effective form of synchronous interaction. POTS is today by far the most demanded synchronous service. This service has evolved into N to N audioconference or videoconference facilities. Computers in general and the Internet have also had primitive types of character oriented synchronous interactive services for a long time, like TALK, IRC, ... Today low quality voice and video over the Internet is also common practice with applications like, CU-SeeMe, IVS, VAT, ... Audiovisual broadcasting is also a highly demanded type of remote synchronous interaction which has been done since many years. Although broadcasting has really no interaction because the flow of information is unidirectional, it is nevertheless being addressed in the experiments performed for creating new synchronous services. One of the most popular services on the multicast backbone of the Internet, also known as the MBONE, is the conference broadcasting for which a Session Directory (SD) exists where the list of broadcast conferences is displayed in real time. Sophisticated forms of remote synchronous interaction requiring good quality telepresence demand more bandwidth and more reliable communications to achieve a proper interaction. Therefore for setting up large sacle experiments like the RACE/ACTS Summer Schools [2,5,6,9] a complex collaboration among a large number of organizations has been needed. In addition, the availability of large …

Isabel: an application for real time collaboration with a flexible floor control

Isabel is a P2P like multipoint group collaboration tool for the Internet, which implements an innovative service concept for synchronous collaborations based on a flexible and programmable floor control. This approach leads to a more natural and effective management of collaboration sessions. The flexible and programmable floor control incorporates the experience gained in many years of service trials with real users in distributed conferences, classrooms or meetings. The main conclusion after all those trials is that services should use more or less the same media components (audio, video or application sharing), but differ in the floor control model used. The flexible floor control is especially well suited for multipoint audience interconnection in distributed classrooms, conferences, meetings, etc. The development of Isabel started in 1993 for the distribution of the RACE Summer Schools on Advanced Broadband Communication (ABC93-6) where the early versions of this service concept were developed and tuned. The effectiveness of the Isabel service concept has been proven and enhanced since then in many other distributed events, such as Global360x, IDC9x, Global IPv6 Summitts, Telecom I+D, etc. The adaptation of Isabel to the broadband Internet (including VPNs, IPv4/IPv6 transition scenarios, mixtures of unicast and multicast) has reached maturity recently

ISABEL - Experiment Distributed Cooperative Work Application over Broadband Networks

Users are looking towards ATM technology as a suitable solution for specific applications in the new field of distributed multimedia. The aim of ISABEL is to take benefit of the new broadband technology in order to provide a good access to new distributed multimedia facilities. The application has been developed to cover two main fields: distance learning activities between two or more real conference rooms and a flexible framework to configure many different computer support cooperative work (CSCW) scenarios. The paper describes the functionality of ISABEL and its use to support real experiments.

The Lotosphere Design Methodology

This chapter provides an application oriented description of the LOTOS Design Methodology produced in the Lotosphere project. This design methodology is a formally based stepwise refinement approach to system design, conceived to give formal support to an industrial design process, in order to achieve high quality designs.

A Quality of Service Assessment Technique for Large-Scale Management of Multimedia Flows

This paper presents the concept and preliminary experiments of a system for assessing on the Quality of Service of multimedia flows. The goal is to devise a mechanism that allows a service provider to take action whenever poor quality of service is detected in the delivery of multimedia flows. Such procedure is fully automatic since it is based on a goodness-of-fit test between source and destination packet interarrival histograms. If the null hypothesis of the test is accepted the flow is marked as in good standing, otherwise it is marked as anomalous and the network management system should take action in response. The proposed technique is analyzed in terms of hardware complexity and bandwidth consumption. The results show this technique is feasible and easily deployable at a minimum hardware and bandwidth expense.

A Collaborative Environment Integration Layer for Activity Orientation

This paper proposes the creation of an architectural layer for integration of all the resources and members participating in a given collaborative activity into a unified framework which is referred as the collaborative environment integration layer (CEIL). This layer is considered a necessary step for integrating with open standards all the collaborative resources or components into a tightly coupled collaborative environment which implements activity orientation. The proposal considers two architectural elements. The first element is the collaborative environment description language (CEDL), which is the formal language for describing all the elements and associated parameters relevant for modeling and managing a collaborative environment. The second one is the collaborative environment management interface (CEMI), which is the unified interface which provides uniform management and configuration of the collaborative components of an environment. This layer includes accurate descriptions of the virtual organizations associated to collaborative activity, including participants, roles, rights, hierarchies, etc being able to model the variety of existing virtual organization models

Distributed global conferences over hetergeneous networks

Many multimedia applications have been developed during the past years for supporting co-operative work, tele-teaching and many other activities involving groups of persons distributed at different locations and communicating by means of telecommunication networks. Most of this effort has been devoted, till now, to deal with technical problems: network design and network interconnection, applications, etc. It is now becoming increasingly important to tackle the problems related to the organisation of these activities as distributed events, involving sophisticated equipment and the users of the system. It will be shown that the organisation of a distributed event is qualitatively different from the organisation of a similar event in a single place and during a specific period of time.

Managing Distributed Conferences with ISABEL

ISABEL provides a platform for development of new multimedia services, including distributed conferences, with presentations and attendances located in rooms at different sites. ISABEL permits the definition of new services adapted to the specific requirements of each case. It builds its own communication network providing a uniform Quality of Service through the variety of interconnected sub-networks. Nevertheless, technical problems are not the only problems on this kind of events. Planning, management and realisation of a Distributed congress covering several continents are issues directly related with technology management and co-operation between persons and computer systems. This paper reviews technical and organisation problems involved in the realisation of a Distributed Congress and proposes an organisation model based on the ISABEL platform to deal with them.