Juan Antonio de la Puente

An Open Ravenscar Real-Time Kernel for GNAT

This paper describes the architecture of ORK, an open source real-time kernel that implements the Ravenscar profile for the GNAT compilation system on a bare ERC32 computer. The kernel has a reduced size and complexity, and has been carefully designed in order to make it possible to build reliable software for on-board space applications. The kernel is closely integrated with the GNAT runtime library, and supports Ada tasking in an efficient and compact way.

A dual-band priority assignment algorithm for dynamic QoS resource management

Future high-quality consumer electronics will contain a number of applications running in a highly dynamic environment, and their execution will need to be efficiently arbitrated by the underlying platform software. The multimedia applications that currently execute in such similar contexts face frequent run-time variations in their resource demands, originated by the greedy nature of the multimedia processing itself. Changes in resource demands are triggered by numerous reasons (e.g. a switch in the input media compression format). Such situations require real-time adaptation mechanisms to adjust the system operation to the new requirements, and this must be done seamlessly to satisfy the user experience. One solution for efficiently managing application execution is to apply quality of service resource management techniques, based on assigning and enforcing resource contracts to applications. Most resource management solutions provide temporal isolation by enforcing resource assignments and avoiding any resource overruns. However, this has a clear limitation over the cost-effective resource usage. This paper presents a simple priority assignment scheme based on uniform priority bands to allow that greedy multimedia tasks incur in safe overruns that increase resource usage and do not threaten the timely execution of non-overrunning tasks. Experimental results show that the proposed priority assignment scheme in combination with a resource accounting mechanism preserves timely multimedia execution and delivery, achieves a higher cost-effective processor usage, and guarantees the execution isolation of non-overrunning tasks.

A Software Architecture Evaluation Model

The fulfilment of quality requirements is fundamental for the success of software-intensive systems. This fact forces companies to quantify the quality requirements at the moment of their specification, and to evaluate these requirements in all the results of the design process, both the by-products and the end system. The definition of the software architecture is one of the most important and early decisions of the design process, with a strong influence on the final quality of the product; therefore its evaluation should be made as early as possible, before the design is complete. This paper presents a software architecture evaluation model considering the software architecture as a final product itself and also as an intermediate product of the design process.

Mode Change Protocols for Predictable Contract-Based Resource Management in Embedded Multimedia Systems

Media processing in High-Quality Multimedia Embedded Systems (HQMES) has real-time constraints. Timely processing and rendering of video frames and audio samples is essential to meet user expectations. The nature of incoming media suffers unforeseen variations which have different resource requirements. Therefore, HQMES have to integrate policies for efficiently and smoothly adapting to these changes. Mode change protocols allow applications to switch their state (for instance, to transition from one quality level to another) by controlling the way in which the application tasks change from one state to another. This paper provides a solution for timely mode change protocols based on a contract model between applications and the execution platform. A new mode change algorithm, progressive mode change protocol, is introduced for applications with no tolerance to data loss during their transitions. The execution platform is based on a quality of service resource manager (QoSRM) that arbitrates the greedy execution of multimedia applications, and that is implemented on top of the services of a real-time operating system. A task model and a temporal characterization of multimedia application tasks is also presented as the basic platform for the QoSRM operation. Validation experiments show stable execution of applications with the proposed task characterization and progressive mode change protocol.

The design and implementation of the open Ravenscar kernel

This paper describes the design and implementation of Open Ravenscar Kernel (ORK), an open-source real-time kernel of reduced size and complexity, for which users can seek certification for mission-critical space applications. The kernel supports Ada 95 tasking on an ERC32 (SPARC v7) architecture in an efficient and compact way. It is closely integrated with the GNAT runtime library and other tools.

Reference architecture for robot teleoperation:: development details and practical use

This work has been partially supported by the Spanish Government Programmes for Research in Electrical Power (project PIE-041049), and for Technological Actuation in Industry (PAUTA projects 753/ 95 y 53/96). TRON is supported inside EUREKA– MAINE program (EU1565).

Reliable Software Technologies — Ada-Europe’ 99

While there are appear to be many ways in which real-time Ada systems can be designed, it is observed that they can be described using four architectural families: the Timeline, Event-Driven, Pipeline, and Client-Server architectures. This paper describes the principal characteristics of each of these architecture families with respect to their ability to provide bounded application response times, their cost, and safety at a high level. In addition, the use of important Ada constructs for each architecture family is discussed, and examples of application domains that use each of these architectures are identified.

Software Architecture for a Robot Teleoperation System

Abstract The success of certain applications heavily depends on its capability to be modified and adapted to different operations and environments. This paper presents the main issues in the development of a robot teleoperation system whose main goal is to operate a robot that performs maintenance activities in nuclear plants. The capability to adapt its operation to different jobs and operational environments is one of the most important requirements. The approach taken is based on the development of a generic software architecture for this kind of systems. A domain analysis was performed for identifying the most commonly used components in these applications. The resulting architecture was implemented integrating code written in different languages (Ada and C) and commercial tools. The resulting architecture has been successfully tested. The robot controller (which is the most important subsystem) has been reused for implementing specialized mechanical robot tools.

The IPTES environment: Support for incremental, heterogeneous and distributed prototyping

This paper summarizes the support for incremental, heterogeneous and distributed prototyping of real time systems developed as a part of the IPTES environment. After describing the overall architecture of the environment and related approaches, the paper focuses on the internal levels of the environment.IPTES environment supports the incremental development of Real-Time Systems under a spiral life cycle model. The user starts from a SA/RT description enhanced with an executable VDM dialect for minispecifications. Both parts are converted into high level timed Petri nets (HLTPN). The partition of the model at the SA/RT level is reflected at the HLTPN as distributed subnets. A distributed prototype execution implies the joint execution of distributed subnets. Finally, some parts of the prototype could be substituted by actual target code and executed with the rest of the prototype. This is the concept of heterogeneous prototype supported by IPTES tools. A communication protocol to allow the interchange of information while executing has been designed and implemented in the IPTES environment.A detailed description of the Real Time Object Communication Layer (RTOC), its constituent primitives and internal algorithms is presented. This discussion provides the background to understand the behavior of the High Level Timed Petri Net Kernel (HLTPNK) to execute distributed subnets and the Run Time Adaptation Kernel (RTAK) to control the execution of target code as users of the RTOC.Finally, the method used to generate successive versions of the protocol and kernel modules in order to reduce the risks during the implementaton is outlined.

Hierarchical scheduling with ada 2005

Hierarchical scheduling is a basic technique to achieve temporal isolation between applications in high-integrity systems when an integrated approach is opted for over traditional federation. While comparatively heavyweight approaches to hierarchical scheduling have been prevailing until now, the new scheduling features of Ada 2005 enable lighter-weight techniques to be used. This will expectedly result in increasing the efficiency and flexibility of hierarchical scheduling, thus enabling new ways to developing critical applications in Ada. The paper explores the new opportunities opened by Ada 2005 and proposes some concrete techniques for implementing hierarchical scheduling in the new version of the language.