1 MINISTERIO DE CIENCIA Y TECNOLOGÍA SECRETARÍA DE ESTADO DE POLÍTICA CIENTÍFICA Y TECNOLÓGICA DIRECCIÓN GENERAL DE INVESTIGACIÓN SUBDIRECCIÓN GENERAL DE PROYECTOS DE INVESTIGACIÓN JORNADAS DE SEGUIMIENTO PROYECTOS EN TECNOLOGÍAS DE LA INFORMACIÓN DESCRIPCIÓN DE RESULTADOS Referencia del proyecto: Título: Investigador principal: Dirección de contacto: TIC C03 Desarrollo integrado de sistemas integrados distribuidos Juan Antonio de la Puente Alfaro ETSI Telecomunicación UPM Ciudad Universitaria s/n Madrid Se trata de un proyecto coordinado? Sí Subproyecto 1: Investigador principal: Dirección de contacto: Subproyecto 2: Investigador principal: Dirección de contacto: Subproyecto 3: Investigador principal: Dirección de contacto: TIC C03-01 Juan Antonio de la Puente Alfaro DIT, ETSI Telecomunicación UPM Ciudad Universitaria s/n Madrid TIC C03-02 Joan Vila Carbó DISCA-EUI; Universitat Politécnica de Valencia Camí de Vera s/n Valencia TIC C03-03 Michael González Harbour Dep. Electrónica y Computadores, Univ. De Cantabria Avda. de los Castros s/n Santander
2 1. PROJECT OBJECTIVES The global aim of the project is to make progress in defining methods and building tools for developing distributed embedded systems in an integrated fashion. Different abstraction levels are considered, including operating systems, distributed object platforms, and architectural design. More in detail, the following kinds of results are expected: Real time operating systems o Real-time kernels for minimal embedded real-time systems (POSIX.13 PSE-50). o Real-time kernels for high-integrity embedded real-time systems (ISO 15942) o Run-time support and development toolkit for embedded systems based on RT-Linux. o Support for quality of service in real-time multimedia systems. Distributed object technology o Run-time support for distributed object platforms o Java virtual machine for CORBA / POSIX platforms o Distributed object technology for telecommunication services management. Software architectures o UML adaptation to real-time systems modelling o Methodological guidelines for embedded systems development with UML o Temporal analysis tools for UML-based design environments o Component-based development methods for embedded systems o Architectural styles and reference architectures for real-time systems 2. LEVEL OF SUCCESS Significant results have already been achieved in most of the above objective areas, with no special difficulties in any of them. Some of these areas have benefited from synergy from other concurrent projects. The next paragraphs describe in detail the most important results within each of the above target areas. 2.1 Real-time operating systems Real-time kernels for minimal embedded real-time systems (POSIX.13 PSE-50). A real-time kernel for small embedded systems called MaRTE OS (Minimal Real-Time Operating System for Embedded Applications) has been developed by the UC team. It is a real-time kernel for embedded applications that follows the Minimal Real-Time POSIX.13 subset, providing both the C and Ada language POSIX interfaces. It allows crossdevelopment of Ada and C real-time applications. Mixed Ada-C applications can also be developed, with a globally consistent scheduling of Ada tasks and C threads. Performance metrics have shown the kernel to be extremely efficient. The kernel has been distributed as free software, and is being used by several institutions in the US and in Europe. It is also being used as an educational tool for practicing with the development of POSIX-compliant real-time applications. MaRTE OS has been implemented for a bare PC (386 processor or above). It is currently being ported to a Motorola 683XX microcontroller. In addition, MaRTE OS is being extended with a set of services for user-defined scheduling that will enable application developers to use their own scheduling policies, and not just those defined in the standard. A proposal for incorporating these services into the POSIX standard has been made and is currently being discussed by the POSIX real-time working group.
3 Real-time kernels for high-integrity embedded real-time systems (ISO 15942). The main result in this area is the Open Ravenscar Real-Time Kernel (ORK), an opensource implementation of the Ravenscar profile 1 for the SPARC-v7 and PC architectures which has been developed by the UPM team. The kernel is part of an integrated development environment based on the GNAT compilation system and the GDB/DDD debugging tools which is available under a GPL licence. An Ada cross-compilation system for MC68000 targets based on the RTEMS kernel is also under development. Run-time support and development toolkit for embedded systems based on RT-Linux. The first result in this area is minimal distribution of Linux with a series of features for embedded and real-time operation which has been developed by the UPV team. Some minor features and a well organized distribution accessible via web are still pending. A graphical tool that defines and guides the whole process development of an embedded system under RT-Linux has also been implemented by the same team. Some refinements to this process and extensive debugging are still required. Other results include some scheduling extensions and a CAN driver for RT-Linux. The scheduling extensions allow designers to structure complex real-time tasks into a sequence of mandatory and optional components which are scheduled in two levels. A computational model for a software architecture based on this tow-level decomposition has also been developed. Finally, new mode change protocols for real-time systems are being investigated in this framework. Support for quality of service in real-time multimedia systems. A quality of service manager architecture has been designed and implemented by the UPM team. Its operating principles are based on the idea of negotiating QoS levels and resource assignments with multimedia applications. The QoS requirements are translated to the operating systems mechanisms so that the level of resources of each application is guaranteed, and the performance of the system is monitored in order to optimize its operation. Iin relation to this subject, the UPV team has worked on a study of optimal bandwidth and buffer reservation in real-time transmission. This is a contribution related to the techniques of estimating resource reservation for achieving a given QoS. It has been done only for the case of Mpeg transmissions, but some generalization of this technique to embedded systems for multimedia purposes is expected Distributed object technology Run-time support for distributed object platforms Support for Java objects in RT-Linux: Some different profiles of minimal distributions of Java have been adapted for RT-Linux by the UPV team. The degree of achievement of this goal is only of 50% because no real-time features have been still considered in this development. 1 The Ravenscar profile is a subset of Ada tasking for high-integrity systems. It is currently part of the ISO guidelines for high-integrity Ada software.
4 Java virtual machine for CORBA / POSIX platforms Although the development of a Java Virtual Machine on top of MaRTE OS had been planned by the UC team for starting in mid-2000, we have delayed this task until 2002 because the community is still developing a standard for real-time Java, that will have a deep impact in our work. Two different approaches are being followed, and two different real-time Java proposals have appeared recently. The use of Java for the implementation of end user access application from terminals with limited capacity or performance (PDA s, cellular phones, etc.) has been investigated by the UPM team. A minimum ORB conforming to CORBA specifications has been implemented for smart cards supporting Java (Cyberflex Access Javacard). Distributed object technology for telecommunication services management. A first set of results in this area refer to life cycle management for users and services. Life cycles for advanced telecom services, as well as subscribers and end users, have been formalised using UML diagrams by the UPM team. The emphasis is in the exploitation phase and the characterisation of general and service specific attributes for the service life cycle management, and on attributes that characterise users and subscribers in the context of the business model. CORBA based applications for service template management and for subscription management have been developed in this framework. A full blown prototype integrating service and subscription management together with front end components to access and service session subsystems has been designed, implemented and validated. Other results are related to configuration management for service nodes and user terminals. First, a feasibility study for the use of object-oriented programming languages has been performed. A UML profile for the specification of configuration management information models has been designed. The UML profile is suitable for the specification and instrumentation of configuration management in services and applications implemented as CORBA based distributed components. A CORBA based prototype for the configuration management of advanced component based telecom services has been implemented. Emphasis has been put on deployment, activation/deactivation, component properties and security. The implementation includes a CORBA compliant event service implemented by DIT-UPM for the integration of subsystems and components within the configuration management system. Finally, security requirements for distributed component based services and applications are being identified. The CORBA security service specification is been considered for the implementation of these security requirements 2.3. Software architectures UML adaptation to real-time systems modelling A new UML profile for real-time systems, called PPOOA, has been developed by UPM. It includes two kinds of extensions of the UML meta-model. The first one is a new modelling element called CFA (Causal Flow of Activities) that models a response to an event as a chain of activities. The UML meta-model has also been extended to include new component stereotypes supporting explicit concurrency, such as periodic and aperiodic processes and different kinds of coordination mechanisms. These components have attributes which can be used to characterize the temporal response of real-time systems. The PPOOA profile has been implemented on CASE prototype tool. Some difficulties have been encountered with on-going evolution of the UML standard.
5 Methodological guidelines for embedded systems development with UML Design guidelines for real-time architectures and components are under development by the UPM team. The guidelines provide help in identifying and selecting software components, as well as modelling the above described CFA elements. Temporal analysis tools for UML-based design environments The UC team has developed a model for representing the temporal and logical elements of real-time applications, called MAST. This model allows a very rich description of the system, including the effects of event or message-based synchronization, multiprocessor and distributed architectures as well as shared resource synchronization. The model is directly obtainable from a description of the system design using a UML tool. A system representation using this model is analyzable through a set of tools that has been developed within the MAST suite, including worst-case schedulability analysis for hard timing requirements, and discrete-event simulation for soft timing requirements. Although the current model only includes fixed priority systems, it is conceived as an open model and is easily extensible to accommodate other kinds of systems. The tools that are already available allow schedulability analysis and priority assignment for distributed real-time applications built under the so-called linear model. These tools have been distributed as free software. We are currently finishing the MAST toolset adding into it the discrete-event simulation capability as well as support for the schedulability analysis of systems modelled under the multiple-event model. In addition, we have developed a methodology and a framework for building an analyzable real-time model of an object-oriented system using a UML CASE tool. The real-time model is formulated by a new UML view named "MAST_RT_View". This view allows the designer to gradually build the real-time model according to the phase of the development process, to feed data into the analysis tools, and to bring the relevant timing responses back into the model. The MAST_RT_View has three models: the processing capacity of the hardware/ software platform; the timing behavior of the application logical components; and the workload and the timing requirements of each real-time situation to be analyzed. This view is analyzable by the MAST set of tools. Component-based development methods for embedded systems A set of guidelines and attributes have been defined for a proper definition of software components has been develop dby the UPM team, with especial focus on non-functional or quality aspects. In addition, standard notations (with full compatibility to the standard UML) have been selected. Several models or views of UML are dealt with. Operational methods for the identification of software components from legacy software have been experimented. These methods are based on measurement of cohesion and coupling indicators, and on the clustering of software elements in order to maximize cohesion. The degree of advancement of the task is 35%. Operational methods for testing of components and systems built on them are being studied. Very specially, the degree of coverage of system requirements with respect to the components used is under way. The task is at 70%. Based on the description of components, and restrictions and decisions for the system architecture, a method and tool implementation for selection of the proper set of components has been produced. The task advancement is 85%. Architectural styles and reference architectures for real-time systems The UC team has defined a reference architecture for industrial controllers based on the PINROB interface, as a portable interface for industrial robots. In this architecture each element is defined as a software component that includes all the information necessary to perform a schedulability analysis using the UML-MAST modelling technique. An application
6 involving several robots, sensors and machines can be easily defined using the defined components. We are currently in the process of implementing the fundamental components that have been defined, in order to demonstrate this technology. A two level architecture and scheduling model for developing the software of an autoguided vehicle under RT-Linux has been defined by the UPV team. The degree of accomplishment of this goal is 70%. A newer version of this software including aperiodic tasks is now under development. A reference software architecture for embedded multimedia systems has been developed by the UPM team. The architecture has been designed with an emphasis on QoS management, and is currently being assessed and improved. 3. RESULTS 3.1 Doctoral dissertations A total of 5 Doctoral Thesis have been presented during the project, and three more are scheduled to be defended in the next moths. Some others are expected to be presented in 2002 (see appendix for the details) Publications A total of 47 papers have been published or accepted for publication in the framework of the project (see appendix for the details). 3.3 Technology transfer The GNAT/ORK compilation system is being evaluated by a number of companies working for the European Space Agency (ESA). In particular, the Astrium group has selected this environment for the pre-development project of the Galileo Navigation Signal Generator Unit. Some dissemination activities related to the MARTE kernel and the MAST evironment have been performed: o The following tutorial was given at an international conference: González Harbour, M., Tutorial: Real-Time POSIX. International Conference on Reliable Software Technologies, Ada-Europe'2000, Potsdam, Germany, Junio, The following invited talks have been given on the technologies developed within this project: o "MAST: Entorno para el modelado y análisis de aplicaciones de tiempo real", Universidad de Málaga, Septiembre o "MARTE: Implementación mínima de POSIX de tiempo real para aplicaciones empotradas", Universidad de Málaga, Septiembre o "MaRTE OS: A Minimal Real- Time POSIX OS for Embedded Applications", Vasteras University, Suecia, Diciembre o "Schedulability Analysis of distributed systems, MAST", European Space Agency (ESA-ESTEC), Noordwijk, Holanda, Junio o "Real-Time POSIX, MarteOS", European Space Agency (ESA-ESTEC), Noordwijk, Holanda, Junio The UC group has been actively participating in the POSIX real-time working group and has proposed an interface for application-defined scheduling based on the results of this project, to be included in a future revision of the ISO/IEC standard.
7 3.4 Other national and international projects CARTS - Computer Aided Architectural Analysis of Real-Time Systems. IST Programme, ESAPS - Engineering Software Architecture, Processes and Platforms for System-Families. ITEA Low-Cost On-Board Software Development Toolkit. ESA/ESTEC OBOSS - Experimental Assessment of Value Added to Software Reuse by Ada 95 Technology. ESA/ESTEC Open Ravenscar Real-Time Kernel. ESA/ESTEC Quality of Service for Trimedia Applications. Philips Research, Collaboration Contact and information exchange with Schlumberger (France), provider of Cyberflex Javacards, regarding the implementation of the CORBA compliant minimum ORB for smart cards. Contact and information exchange with Lucent Technologies (Spain) regarding the implementation of the CORBA compliant event service implemented for the configuration management system. Lucent Technologies partly funded a master thesis related to this implementation.
8 APPENDIX Detail of results 1. Doctoral dissertations UPM 1. Calidad de servicio en sistemas multimedia empotrados mediante gestión dinámica de recursos (Quality of Service in multimedia embedded systems by means of dynamic resource management). Author: Marisol García-Valls. Supervisors: Alejandro Alonso and Juan A. de la Puente. July Contribución a la gestión de configuración en servicios avanzados de telecomunicación con componentes distribuidos. (Contribution to configuration management in component based advanced telecom services). Author: José Fernán Martínez. Supervisor: Juan Carlos Yelmo. To be presented in December,2001. UPV 1. Mode Change Protocols for Real-Time Systems. Author: Jorge Real. Supervisor: Alfons Crespo. March European Ph.D. 2. Planificación en Sistemas Multiprocesadores de Tiempo Real (Scheduling in Multiprocessor Real-Time Systems). Autor: Sergio Sáez Barona. Supervisor: Joan Vila. June, Flexible Real-Time Linux. A new environment for Flexible Hard Real-Time Systems. Author: Andrés Terrasa. Supervisors: Ana García-Fornes, Vicente Botti. February, European Ph.D. 4. Reserva eficiente de recursos en redes para transmisión en tiempo real (Efficient reservation of network resources for real-time transmisison). Author: Enrique Hernández. Supervisor: Joan Vila. June, UC 1. Servicios de planificación en sistemas operativos de tiempo real para aplicaciones empotradas (Scheduling services in real-time operating systems for embedded applications).autor: Mario Aldea. Supervisor: Michael González Harbour. Defense planned for the first quarter of Metodología de modelado y análisis de sistemas distribuidos de tiempo real estricto basada en componentes (Component-based modelling and analysis methodology for hard real-time distributed systems). Autor: Julio Medina, Supervisor: José María Drake. Defense planned for the first quarter of Publications UPM 1. Software Architecture for Product Families, M. Jazayeri, A. Ran, F. Van der Linden (eds.). Chapter Software Architecture Assessment, J.C. Dueñas, A. Alonso, W. Lopes, María S. García, J. A. de la Puente, G. León. Addison-Wesley, ISBN: Railway-Control Product Families: The Alcatel TAS Platform Experience, J. Mellado, M. Sierra, A. Romera, J.C. Dueñas,, in Proceedings of the Third International Workshop on Software Architectures for Product Families. Lecture Notes in Computer Science 1951, Springer-Verlag ISBN: Pg: A First Assessment of Development Processes with Respect to Product Lines and Component Based Development. R. Cerón, J.C. Dueñas, J.A. de la Puente, in Proceedings of the Third
9 International Workshop on Software Architectures for Product Families. Lecture Notes in Computer Science 1951, Springer-Verlag ISBN: Pg: Juan A. de la Puente, José F. Ruiz, Juan Zamorano, Rodrigo García, and Ramón Fernández- Marina. ORK: An Open Source Real-Time Kernel for On-Board Software Systems. In DASIA Data Systems in Aerospace. Montreal, Canada, Juan A. de la Puente, José F. Ruiz, Juan Zamorano. An Open Ravenscar Real-Time Kernel for GNAT. In Hubert B. Keller and Erhard Plödereder (Eds.) Reliable Software Technologies. Ada-Europe 2000 Lecture Notes in Computer Science, Springer-Verlag (2000). 6. Scarab Service Management Subsystem: Subscription and Configuration Management for Advanced Telecommunication Services. J. F. Martínez, J.C. Yelmo. TELEC'2000, July 2000, Santiago de Cuba, Cuba. 7. Criteria for Partitioning Reference Architectures, R. Capilla, J. C. Dueñas, R. Cerón, in "6th International Conference on Information Systems Analysis and Synthesis ". Florida, USA, Julio Alejandro Alonso and Juan Antonio de la Puente. Implementation of Mode Changes with the Ravenscar Profile. Ada Letters, XXI, 1, March Juan A. de la Puente, Juan Zamorano, José F. Ruiz, Ramón Fernández and Rodrigo García The Design and Implementation of the Open Ravenscar Kernel. Ada Letters, XXI, 1, March Architectural evolution, systems that grow., J. C. Dueñas, en "IST Component Based Software Engineering Workshop, Ferentino, Italia, June European Commission. 11. José F. Ruiz, Juan A. de la Puente, Juan Zamorano, Ramón Fernández-Marina. Exception Support for the Ravenscar Profile. Ada Letters, XXI, 3, September Juan Zamorano, José F. Ruiz and Juan A. de la Puente. Implementing Ada.Real_Time.Clock and absolute delays in real-time kernels. In D. Craeynest and A. Strohmeier (Eds.) Reliable Software Technologies. Ada-Europe Lecture Notes in Computer Science, Springer-Verlag (2001). 13. Tullio Vardanega, Rodrigo García, and Juan A. de la Puente. An Application Case for Ravenscar Technology: Porting OBOSS to GNAT/ORK. In D. Craeynest and A. Strohmeier (Eds.) Reliable Software Technologies. Ada-Europe Lecture Notes in Computer Science, Springer-Verlag (2001). 14. Jose Luis Fernandez-Sanchez and Antonio Monzón. Extending UML for Real-Time Component Based Architectures. The Fourteenth International conference on Software and Systems Engineering & their Applications (ICSSEA 2001), Paris, December 2001 UPV 1. Flexible Real-Time Linux. A Flexible Hard Real-Time Environment. A. Terrasa, A. García- Fornes, V. Botti. Real-Time Systems Ed.: Kluwer Academic Publishers (Accepted) Year: A Tool for Customizing RT-Linux to Embedded Systems. Josep Vidal, Pau Mendoza, Ismael Ripoll, Juan Vila. Real-Time Linux Workshop Milano (Italy) Nov To appear soon. 3. Integrated Dynamic Priority Scheduler for RTLinux. Patricia Balbastre & Ismael Ripoll. Real- Time Linux Workshop Milano (Italy) Nov To appear soon.
10 4. Intelligent Sensors on Minimal Embedded RTLinux Version. P. Pérez, G. Benet, J. E. Simó, F. Blanes. RTLinux Workshop. Milan Nov To appear soon. 5. Using RT-Linux for developing real-time embedded systems. Pau Mendoza, Joan Vila, Silvia Terrasa, Patricia Balbastre and Ismael Ripoll. IFAC Conference on New Technologies for Computer Control ( 2001 ). Hong-Kong (China) Nov To appear soon 6. Intelligent Distributed Sensors Using Embedded RTLinux on a CAN Network. P. Pérez, G. Benet, J. E. Simó, F. Blanes. "IEEE RTSS Symposium. London Dec To appear soon. 7. Developing CAN based networks on RT-Linux. P. Mendoza, J.Vila, I. Ripool, S. Terrasa, P.Pérez. 8th. International Conference on Emerging Technologies and Factory Automation. Proceedings of the ETFA Ed. IEEE-CS Press. ISBN Warsaw (Poland) Oct An Optimal Method for Allocating Buffer and Bandwidth for MPEG Traffic in a Network Node. E. Hernández, J.Vila. Proceedings of the 26th Euromicro Conference. Ed. IEEE-CS Press. ISSN: ISBN Warsaw (Poland). 4-6 Sep Offsets for Scheduling Mode Changes. J. Real and A. Crespo. Euromicro Conference on Real- Time Systems, 2001 (Selected for publication in the Real-Time Systems Journal). 10. A Semantics for Dynamic Ceiling Priorities in Ada. J. Real, A. Crespo and A. Llamosí. IRTAW Ada Letters XX1, nr Evaluation of a New Reservation Scheme for MPEG Transmission in Highly Available Real- Time Channels. E. Hernández, J. Vila. Lecture Notes in Computer Science. Next Generation Networks (ISSN: ). Vol: 1938 pp: Year A hardware architecture for scheduling complex real-time task sets. S. Sáez; J. Vila; A. Crespo; A. Garcia. Journal of computing and information technology (ISSN ). Ed. University Computing Center. Zagreb, Croatia. Vol.: 8 pp.: Year: On accepting aperiodic transactions in distributed systems. S. Sáez, J.Vila, A. Crespo. IEEE 7th Conference on Real-Time Computer Systems and Applications. Proceedings of RTCSA'2000. Ed. IEEE-CS Press. Hong-Kong(China) Dec Including User-Defined Timing Exception Support in FRTL. A. Terrasa, A. García-Fornes. IEEE 7th Conference on Real-Time Computer Systems and Applications. Proceedings of RTCSA'2000. Ed. IEEE-CS Press. Hong-Kong(China) Dec A Fast Method to Optimise Network resources for Video-on Demand Transmission: E. Hernández, J.Vila. 26th Euromicro Conference. Multimedia and Communications. Proceedings of the 26th Euromicro Conference. Ed. IEEE-CS Press. Maastricht (The Netherlands) 5-7 Sept Soft Aperiodic Task Scheduling on Hard Real_Time Multiprocessor Systems. S. Sáez, J.Vila, A. Crespo. IEEE 6th Conference on Real-Time Computer Systems and Applications. Proceedings of RTCSA'99. Ed. IEEE-CS Press. Hong-Kong(China) Dec Real-Time Synchronization between Hard and Soft Tasks in RT-Linux. A. Terrasa, A. García- Fornes IEEE 6th Conference on Real-Time Computer Systems and Applications. Proceedings of RTCSA'99. Ed. IEEE-CS Press. Hong-Kong(China) Dec An Efficient Resource Reservation Scheme for Highly Available Real-Time Channels. E. Hernández, J.Vila. Proceedings of PDCS'99. Cambridge (MA, EE.UU). 3-6 Nov The Ceiling Protocol in multi-moded Real-Time Systems. J. Real and A. Wellings. Ada Europe 1999 (Best Paper price). LNCS vol 1622
11 20. Dynamic Ceilings and Ada 95. J. Real and A. Wellings. Int. Real-Time Ada Workshop (IRTAW). Ada Letters XIX, nr Implementing Mode Changes with Shared Resources in Ada. J. Real and A. Wellings. Euromicro Conference on Real-Time Systems, UC 1. J.L. Medina Pasaje, M. González Harbour, J.M. Drake Moyano, MAST Real-Time View: A Graphic UML Tool for Modeling Object-Oriented Real-Time Systems. 22th IEEE Real-Time Systems Symposium, Londres, UK, Diciembre, J.L. Medina, J.M. Drake, and M. González Harbour, UML-MAST: Modeling and Analysis Methodology for Real-Time Systems Developed with UML CASE tools. Aceptado para su presentación en el ECSI Forum on Design Languages, FDL'01, September, M. Aldea Rivas and M. González Harbour, POSIX-Compatible Application-Defined Scheduling in MaRTE OS. Proceedings of the Work-in-Progress Session at the 13th Euromicro Conference on Real-Time Systems, Delft, The Netherlands, Junio, 2001, ISBN: , pp. 15, M. González Harbour, J.J. Gutiérrez García, J.C. Palencia Gutiérrez, and J.M. Drake Moyano, MAST: Modeling and Analysis Suite for Real Time Applications. Proceedings of the 13th Euromicro Conference on Real-Time Systems, Delft, The Netherlands, Junio, 2001, ISBN: , pp. 125, Mario Aldea Rivas and Michael González Harbour, MaRTE OS: An Ada Kernel for Real-Time Embedded Applications. Proceedings of the International Conference on Reliable Software Technologies, Ada-Europe-2001, Lovaina, Bélgica, Lecture Notes in Computer Science, LNCS 2043, Mayo, 2001, ISBN: , pp. 305, Michael González Harbour (Editor), Proceedings of the 10th International Real-Time Ada Workshop. ACM Ada Letters, Volume XXI, Number 1, March, 2001, pp. 3, José Javier Gutiérrez García and Michael González Harbour, Towards a Real-Time Distributed Systems Annex in Ada. ACM Ada Letters, Volume XXI, Number 1, March, 2001, pp. 62, Mario Aldea Rivas and Michael González Harbour, Extending Ada's Real-Time Systems Annex with the POSIX Scheduling Services. ACM Ada Letters, Volume XXI, Number 1, March, 2001, pp. 20, Maite Veiga, Michael González Harbour, and Eugenio Villar, Portal Crane Specification in Ada. in G. Gorla, W. Nebel, E. Moser, and E. Villar, "System Specification Experiments on a Common Benchmark", IEEE Design&Test of Computers, July, Gutiérrez García J.J., Palencia Gutiérrez J.C., and González Harbour M., Schedulability Analysis of Distributed Hard Real-Time Systems with Multiple-Event Synchronization. Proceedings of the 12th Euromicro Conference on Real-Time Systems, Stockholm, Sweden., Junio, 2000, ISBN: Gutiérrez García, J.J., y González Harbour, M., A Framework for Developing Distributed Hard Real-Time Applications. Proceedings of the IFAC International Workshop on Real-Time Programming, Palma de Mallorca, in "Real-Time Programming 2000", Elsevier Science, Mayo, 2000, ISBN: Aldea Rivas, M. y González Harbour, M., Early Experience with an Implementation of the
12 POSIX.13 Minimal Real-Time Operating System for Embedded Applications. Proceedings of the IFAC International Workshop on Real-Time Programming, Palma de Mallorca, in "Real-Time Programming 2000", Elsevier Science, Mayo, 2000, ISBN: