Abstract — A memory model based on scoped areas is one of the distinctive features of the Real-Time Specification for Java (RTSJ). Scoped Types ensure timely reclamation of memory and predictable performance. The price to pay for these benefits is an unfamiliar programming model that, at the same time, is complex, requires checking all memory accesses, and rewards design-time errors with run-time crashes. We investigate an alternative approach, referred to as Scoped Types, that simplifies the task of managing memory in real-time codes. The key feature of our proposal is that the run-time partition of memory imposed by scoped areas is straightforwardly mirrored in the program text. Thus cursory inspection of a program reveals which objects will inhabit the different scopes, significantly simplifying the task of understanding real-time Java programs. Moreover, we introduce a type system which ensures that no run-time errors due to memory access checks will occur. Thus a RTSJ-compliant virtual machine does not require memory access checks. The contributions of this paper are the concept of Scoped Types, and a proof soundness of the type system. Experimental results will be described in future work. I.

Abstract. Real-time systems are notoriously difficult to design and implement, and, as many real-time problems are safety-critical, their solutions must be reliable as well as efficient and correct. While higher-level programming models (such as the Real-Time Specification for Java) permit real-time programmers to use language features that most programmers take for granted (objects, type checking, dynamic dispatch, and memory safety) the compromises required for real-time execution, especially concerning memory allocation, can create as many problems as they solve. This paper presents Scoped Types and Aspects for Real-Time Systems (STARS) a novel programming model for real-time systems. Scoped Types give programmers a clear model of their programs ’ memory use, and, being statically checkable, prevent the run-time memory errors that bedevil models such as RTSJ. Our Aspects build on Scoped Types guarantees so that Real-Time concerns can be completely separated from applications ’ base code. Adopting the integrated Scoped Types and Aspects approach can significantly improve both the quality and performance of a real-time Java systems, resulting in simpler systems that are reliable, efficient, and correct. 1

Abstract. Real-time systems are notoriously difficult to design and implement, and, as many real-time problems are safety-critical, their solutions must be reliable as well as efficient and correct. While higher-level programming models (such as the Real-Time Specification for Java) permit real-time programmers to use language features that most programmers take for granted (objects, type checking, dynamic dispatch, and memory safety) the compromises required for real-time execution, especially concerning memory allocation, can create as many problems as they solve. This paper presents Scoped Types and Aspects for Real-Time Systems (STARS) a novel programming model for real-time systems. Scoped Types give programmers a clear model of their programs ’ memory use, and, being statically checkable, prevent the run-time memory errors that bedevil the RTSJ. Adopting the integrated Scoped Types and Aspects approach can significantly improve both the quality and performance of a real-time Java systems, resulting in simpler systems that are reliable, efficient, and correct. 1

ed for the DARPA PCES Capstone Demo We report on our experience with the implementation of the Real-time Specification for Java (RTSJ) in the DARPA Program Composition for Embedded System (PCES) program. Within the scope of PCES, Purdue University and the Boeing Company collaborated on the development of Ovm, an open source implementation of the RTSJ virtual machine. Ovm was deployed on a ScanEagle Unmanned Aerial Vehicle and successfully flight tested during the PCES Capstone Demonstration. ployed in the ScanEagle UAV to implement utation, threat deconfliction algorithms tion between the Boeing Corporation, ersity, DLTech, UCI, WUSTL itecture by focusing one ol, threat assessment, and 1.

Abstract—Hardware transactional memory is a promising synchronization technology for chip-multiprocessors. It simplifies programming of concurrent applications and allows for higher concurrency than lock based synchronization. Standard transactional memory is optimized for average case throughput, but for real-time systems we are interested in worst-case execution times. We propose real-time transactional memory (RTTM) as a time-predictable synchronization solution for chip-multiprocessors in real-time systems. We define the hardware for time-predictable transactions and provide a bound for the maximum transaction retries. The proposed RTTM is evaluated with a simulation of a Java chip-multiprocessor. I.

This paper outlines directions for an evaluation of Real-Time Java suitability to be used in ESA spacecraft onboard software. It starts with an overview of related existing standards and ongoing standardisation efforts, as well as several use cases in the avionics and space domain. Then it identifies steps which should be followed to research how particular Java features match particular requirements of different spacecraft on-board software application domains. The paper takes into account the goals of the upcoming ESA Real-Time Java Assessment Project [1].

Hardware transactional memory is a promising synchronization technology for chip-multiprocessors. It simplifies programming of concurrent applications and allows for higher concurrency than lock based synchronization. Standard transactional memory is optimized for average case throughput, but for real-time systems we are interested in worst-case execution times. We propose real-time transactional memory (RTTM) as a time-predictable synchronization solution for chip-multiprocessors in real-time systems. We define the hardware for time-predictable transactions and provide a bound for the maximum transaction retries. The proposed RTTM is evaluated with a simulation of a Java chip-multiprocessor.

In recent years, various approaches to real-time execution of Java have proven their worth in numerous commercial and defense applications. The Real-time Specification for Java has extended the Java platform with a range of features needed for real-time computing. As the use of real-time Java has become more widespread, the demand for Java in real-time applications with safety requirements has led to an effort to define a new standard—JSR-302 Safety-Critical Java (SCJ). The goal of this standard is to facilitate the creation of safety-critical Java applications capable of certification under standards such as DO 178B level A or IEC61508 for SIL 4. JSR-302 is nearing completion and will soon be released for public review. This paper introduces some of the primary goals, challenges, and proposed solutions for safety-critical Java and its relationship with the Real-time Specification for Java. Keywords: