Pearl at the age of five: Case study of development and application of a common high order realtime programming language

The Programming language PEARL for industrial process automation has been developed since 1969. After extensive studies its final definition was frozen in 1976. Since then considerable experience has been gained with some 25 implementations and 200 applications.With PEARL at the age of three, these experiences are offered as a case study in this paper.The paper starts with a characterization of PEARL by indicating the requirements for such a tool, by classifying it with respect to other language types and by pleading for embedded realtime features. As PEARL has been submitted to ISO for international standardization, the question of how it meets the requirements set up by ISO is more thoroughly answered in Appendix A.The report of experience is given separately for implementation, application, and standardization with as much quantitative results as possible, including compiler behaviour, application areas, and economical benefit.For readers not yet familiar with PEARL a tutorial introduction by means of a simple but completely programmed control problem is given in Appendix B.     

Autonomous control of a prototype solar-powered offshore autonomous underwater vehicle servicing platform via a low-cost embedded architecture

This paper describes the design, implementation, and field-testing of a low-cost autonomous control system on the Platform for Expanding Autonomous Underwater Vehicles (AUV) exploRation to Longer ranges (PEARL). PEARL is a floating, solar-powered platform designed as a servicing station for AUVs. This paper describes the field testing of a prototype system currently without the ability to dock and recharge AUVs. In this prototype, autonomous operations are realized through the open-source MOOS-IvP marine robotics software running on an embedded architecture including a Raspberry Pi microcomputer, Arduino microcontroller, and onboard inertial measurement unit and GPS sensors. A solar charge controller monitors energy system statistics in real-time. Field tests included station-keeping and waypoint missions in a freshwater pond in Orleans, MA. An RMS tracking error of 0.9–2.2 m was achieved during waypoint pattern executions, with an average battery usage of 13% per hour. Net power consumption rate will change due to variations in currents and winds, as well as variations in solar irradiance. The implementation of an autonomous sun-tracking mode to maximize solar panel flux while station-keeping is also evaluated. The field testing results will inform the design of a full-scale PEARL capable of docking with AUVs. This research helps pave the way for autonomous solar-powered service stations in the ocean that can connect the underwater world with space.     

The programming language ‘PEARL’ and its implementation

This paper describes the real time programming language PEARL, its history and design principles and the portability techniques involved in the implementation of a subset of the language on four computer systems.     

基于实时语言和面向方面的形式化开发方法

面向方面方法和实时语言特性应用于实时软件开发工程，将降低实时软件开发的复杂性，而形式化方法将提升系统的可信度。该文提出的一种面向方面的实时软件开发方法AOSDBRTL，它基于经面向方面扩展的形式化方法AO RT Z，在编码阶段应用实时语言PEARL，实现了软件开发各个阶段对面向方面的无缝支持。     

应用形式化与实时语言的面向方面方法

面向方面的软件开发方法是在面向对象开发方法的基础上，在AOP的支持下将贯穿系统的横切关注点提取出来，通过联结方式织入系统功能代码中的软件开发方法，该方法降低了软件开发的复杂性，提高了系统的灵活性和可维护性。形式化和实时语言为面向方面方法贯穿于实时软件开发提供了必要的支持，以形式化方法AO-RT-Z和实时语言PEARL为基础，给出了一种面向方面的实时软件开发框架，实现了软件生命周期各个阶段对面向方面的无缝支持，降低了实时软件开发的复杂性，提升了系统的可信度。     

Testing the PEARL model in the Netherlands and Sweden

The Plant Protection Product Directive (91/414/EEC) stresses the need of validated models to calculate predicted environmental concentrations. The use of models has become an unavoidable step before pesticide registration. The main topic of the research presented here is the validation of the PEARL model for two well-instrumented sites located in the Netherlands and Sweden. First the water transport module was calibrated, and then the solute transport module, keeping unchanged the water transport parameters. The Dutch site is characterised by a sandy soil. PEARL predictions were very satisfactory for both soil moisture content and groundwater level. Predictions for the tracer, bentazone and ethoprophos concentrations in the soil profile were also successful. The Swedish site is characterised by a structured clay soil. PEARL was successful in predicting soil moisture profiles and the draining water. PEARL performed well in predicting the soil concentration of bentazone at different depths, however, it did not predict accurately solute concentration in the drainage water. A sensitivity analysis of the PEARL model performed on the Swedish site showed the greater importance of the pesticide degradation properties over the soil hydraulic properties.     

A safety shell for UML-RT projects structure and methods of the corresponding UML pattern

A safety shell pattern was defined based on a re-configuration management pattern and inspired by the architectural specifications in Specification PEARL. It is meant to be used for real-time applications to be developed with UML-RT as described. The implementation of the safety shell features as defined in Kornecki and Zalewski (Software Development for Real-Time Safety—Critical Applications. Software Engineering Workshop—Tutorial Notes, 29th Annual IEEE/NASA 03, pp 1–95, 2005), namely, its timing and state guards as well as I/O protection and exception handling mechanisms, is explained. The pattern is parameterised by defining the properties of its components as well as by defining the mapping between software and hardware architectures. Initial and alternative execution scenarios as well as the method for switching between them are defined. The goal pursued with the safety shell is to obtain clearly specified operation scenarios with well-defined transitions between them. To achieve safe and timely operation, the pattern must provide safety shell mechanisms for an application designed, i.e., enable its predictable deterministic and temporally predictable operation now and in the future.     

A hardware supported operating system kernel for embedded hard real-time applications

The concept of the kernel, i.e. the time critical part of a real-time operating system, and its dedicated co-processor, especially tailored for embedded applications, are presented. The co-processor acts as a system controller and operates in conjunction with one or more conventional processors in hard real-time environments. It is composed of three physically and clearly separated layers which vary with regard to implementation, speed and complexity. Correspondingly, the model of the operating system kernel is hierarchically structured, and functions are mapped to these layers, observing the inherent parallelism of recognition and handling of different kinds of events expected in such environments and higher level kernel functions such as tasking operations. The operating system functions are supported by the high level real-time programming language constructs. Since many embedded systems are safety related, the software employed must be highly dependable. Therefore, the kernel was proven correct with formal methods, which represents a major innovation in software technology.     

: A distributed real-time logic language

This paper presents a new language that integrates the real-time and distributed paradigms within the framework of a concurrent logic language. Concurrent logic languages (CLLs) are capable of expressing concurrence, communication and nondeterminism in a natural way. That is, the intrinsic parallel semantics of the concurrent logic languages makes them well-suited for distributed programming. The proposed language is particularly suitable for loosely coupled systems and it contains mechanisms for distributed and real-time process control. A new execution model for concurrent logic languages is presented, which enables efficient distributed execution and real-time control. The model is introduced by giving an operational semantics for the language and the new model's implementation is discussed, including the definition of a new abstract machine and its implementation on a network of Unix workstations. Although the sequential core is not optimized, some previous results are discussed, showing the feasibility of the language's execution model for distributed real-time systems. The language is currently being used as the kernel language for a distributed simulation and validation tool for communication protocols.     

: A distributed real-time logic language

This paper presents a new language that integrates the real-time and distributed paradigms within the framework of a concurrent logic language. Concurrent logic languages (CLLs) are capable of expressing concurrence, communication and nondeterminism in a natural way. That is, the intrinsic parallel semantics of the concurrent logic languages makes them well-suited for distributed programming. The proposed language is particularly suitable for loosely coupled systems and it contains mechanisms for distributed and real-time process control. A new execution model for concurrent logic languages is presented, which enables efficient distributed execution and real-time control. The model is introduced by giving an operational semantics for the language and the new model's implementation is discussed, including the definition of a new abstract machine and its implementation on a network of Unix workstations. Although the sequential core is not optimized, some previous results are discussed, showing the feasibility of the language's execution model for distributed real-time systems. The language is currently being used as the kernel language for a distributed simulation and validation tool for communication protocols.     

Portable real-time software for 8-bit microprocessors

This paper discusses a method for developing efficient and portable software for 8-bit microprocessors used in real-time applications. The technique used is to design an ‘intermediate level language’ (ILL) which defines low-level primitives to support the real-time application programming and the constructs of high level languages. Thus, the high level language (HLL) program goes through two stages of translation; first to the ILL code and then to the machine code of a microprocessor. The ILL instruction set developed bridges the gap between high level languages and the poor instruction set of microprocessors. This allows the development of optimized and portable code for the microprocessors. The ILL operations, data types, data organization, control structures, synchronization, communication and multi-tasking facilities are described. The effectiveness of this technique is shown by comparing the code generated by the ILL approach with the code available for a sample real-time application written directly in assembly level language.     

Automated protocol implementation with RTAG

The RTAG (real-time asynchronous grammars) programming language is discussed. The language is based on an attribute grammar notation for specifying protocols. Its main design goals are: (1) to support concise and easily understood expression of complex real-world protocols; and (2) to serve as the basis of a portable software system for automated protocol implementation. The algorithms used in generating implementations from given specifications are sketched, and a Unix-based automated implementation system for RTAG is described     

基于SoC平台的AVS可变长解码器设计

AVS是我国自主制定的音视频编码技术标准。可变字长编解码是AVS标准中的一项重要技术,该文提出了一种基于SoC平台的AVS可变字长解码（VLD）设计。根据AVS变长码表的特点,重新设计合理的变长码表减少时钟消耗,采用c语言和汇编语言进行设计、模拟,并通过了SoC仿真平台验证。在164MHz工作频率下实现满足基准档次6．0级别的AVS高清视频码流的实时解码要求。     

Comparative evaluation of high-level real-time programming languages

Owing to the fast growing need for better means of building real-time systems, a number of representative languages used in real-time programming is surveyed. The evaluation focuses on seven languages which possess explicit real-time features. Based on a categorization of the latter, the seven languages are then compared with respect to their real-time capabilities. The strong points and the limitations of Ada and PEARL, the only high-level real-time languages readily applicable in industrial control environments, are covered in more detail. The evaluation reveals that none of the languages actually used in industry is genuinely real-time. Therefore, a number of new features is suggested for incorporation into existing or future languages and their run-time environments. These proposals are meant to advance the inadequate state of affairs, and also to reignite the discussion of this topic in the real-time community.     

Modeling distributed real-time applications with specification PEARL

The methodology of hardware/software co-design of embedded control systems with Specification PEARL is presented. Hardware and software are modeled with the language Specification~PEARL, which has its origins in standard Multiprocessor~PEARL. Its usefulness is enhanced for modeling hierarchical and asymmetrical multiprocessor systems, and by additional parameters for schedulability analysis. Graphical symbols are introduced for its constructs to enable graphical modeling while maintaining the semantical background. It is meant to be a superlayer for programs, based on the PEARL programming model. To model program tasks, Timed State Transition Diagrams have been defined. The model of a co-designed system is verified for feasibility with co-simulation. The resulting information should be used when considering changes in a current design with the goal of producing a temporally feasible model. To support dynamic re-configurations, configuration management is introduced into the models. Since UML is becoming a de facto standard also for designing embedded control systems, and since Timed State Transition Diagrams and State Chart Diagrams share great similarity, an interface of the methodology to UML 2 is defined, using UML's extension mechanisms.     

An object-oriented real-time programming language

The real-time object model, an extended object-oriented model for describing real-time systems, is described. The design and implementation of RTC++, a programming language that extends C++ on the basis of the real-time object model, are discussed. The schedulability analysis and specification of rigid timing constraints in systems with active objects are reviewed     

A low complexity time-scaling expansion algorithm of speech signals suitable for real time implementation

This paper presents the development and implementation of a variable rate time-scaling expansion system for speech signals, based on the pitch information, in which only the voiced segments are expanded, keeping the unvoiced and silence segments unchanged. The proposed system was first evaluated by computer simulation and then implemented on a digital signal processor (DSP). Time-domain, frequency-domain, mean opinion score (MOS) and diagnostic rhyme test (DRT) evaluations were done to test the actual performance of developed algorithm, which show that the proposed system allows improving the learning level of foreign language students as well as the understanding ability of elderly people. Objective tests also were carried out in order to probe similarity between the original and the expanded signals. Applying an iterative refinement of the C source code it was possible to obtain a real-time implementation. The current implemented algorithm requires 11 kwords program memory and about 9 million of floating point operations per second (MFLOPS).     

基于游戏引擎的交互行为控制器研究

针对游戏中以交互为核心的控制器,研究了它在实际原型系统中所处的层次,以及和其它层的关系.同时分析和补充了硬件指令的传递路径,进而提出一种基于跨平台开源游戏引擎cocos2d-x的实现方法,并对该引擎做了一定的补充与改进.该方法通过从控制器视图捕获硬件传来的指令,以位为单位进行储存与运算,并通过通道的方式来缓冲并管理命令.优势在于易于指令的扩展,并能在语言层级、运行时层级保持实时和高效,同时支持并行输入,此外,还能够很容易应用到现有的项目中.     

具有实时压缩功能的文件系统

提出了一种具有实时压缩功能文件系统的设计思想，并给出了在嵌入式操作系统中实现的具体方案。同时给出了具有实时压缩功能的C函数库的实现方法，并对整个构想进行了初步的验证。