This paper describes the Player/Stage software tools applied to multi-robot, distributed-robot and sensor network systems. Player is a robot device server that provides network transparent robot control. Player seeks to constrain controller design as little as possible; it is device independent, non-locking and language- and style-neutral. Stage is a lightweight, highly configurable robot simulator that supports large populations. Player/Stage is a community Free Software project. Current usage of Player and Stage is reviewed, and some interesting research opportunities opened up by this infrastructure are identified.

This paper evaluates linear models for predicting the Digital Unix five-second host load average from 1 to 30 seconds into the future. A detailed statistical study of a large number of long, fine grain load traces from a variety of real machines leads to consideration of the Box-Jenkins models (AR, MA, ARMA, ARIMA), and the ARFIMA models (due to self-similarity.) We also consider a simple windowed-mean model. The computational requirements of these models span a wide range, making some more practical than others for incorporation into an online prediction system. We rigorously evaluate the predictive power of the models by running a large number of randomized testcases on the load traces and then data-mining their results. The main conclusions are that load is consistently predictable to a very useful degree, and that the simple, practical models such as AR are sufficient for host load prediction. We recommend AR(16) models or better for host load prediction. We implement an online host load prediction system around the AR(16) model and evaluate its overhead, finding that it uses miniscule amounts of CPU time and network bandwidth

Attainment of software performance assurances in open, largely unpredictable environments has recently become an important focus for real-time research. Unlike closed embedded systems, many contemporary distributed real-time applications operate in environments where offered load and available resources suffer considerable random fluctuations, thereby complicating the performance assurance problem. Feedback control theory has recently been identified as a promising analytic foundation for controlling performance of such unpredictable, poorly modeled software systems, the same way other engineering disciplines have used this theory for physical process control.

This paper evaluates linear models for predicting the Digital Unix five-second load average from 1 to 30 seconds into the future. A detailed statistical study of a large number of load traces leads to consideration of the Box-Jenkins models (AR, MA, ARMA, ARIMA), and the ARFIMA models (due to self-similarity.) These models, as well as a simple windowed-mean scheme, are evaluated by running a large number of randomized testcases on the load traces. The main conclusions are that load is consistently predictable to a useful degree, and that the simpler models such as AR are sufficient for doing this prediction.

Abstract not found

Knit is a new component definition and linking language for systems code. Knit helps make C code more understandable and reusable by third parties, helps eliminate much of the performance overhead of componentization, detects subtle errors in component composition that cannot be caught with normal component type systems, and provides a foundation for developing future analyses over C-based components, such as cross-component optimization. The language is especially designed for use with component kits, where standard linking tools provide inadequate support for component configuration. In particular, we developed Knit for use with the OSKit, a large collection of components for building low-level systems. However, Knit is not OSKit-specific, and we have implemented parts of the Click modular router in terms of Knit components to illustrate the expressiveness and flexibility of our language. This paper provides an overview of the Knit language and its applications.

Research over the past decade has revealed that modeling software architecture at the level of components and connectors is useful in a growing variety of contexts. This has led to the development of a plethora of notations for representing software architectures, each focusing on different aspects of the systems being modeled. In general, these notations have been developed without regard to reuse or extension. This makes the effort in adapting an existing notation to a new purpose commensurate with developing a new notation from scratch. To address this problem, we have developed an approach that allows for the rapid construction of new architecture description languages (ADLs). Our approach is unique because it encapsulates ADL features in modules that are composed to form ADLs. We achieve this by leveraging the extension mechanisms provided by XML and XML schemas. We have defined a set of generic, reusable ADL modules called xADL 2.0, useful as an ADL by itself, but also extensible to support new applications and domains. To support this extensibility, we have developed a set of reflective syntax-based tools that adapt to language changes automatically, as well as several semantically-aware tools that provide support for advanced features of xADL 2.0. We demonstrate the effectiveness, scalability, and flexibility of our approach through a diverse set of experiences. First, our approach has been applied in industrial contexts,

Abstract. DataScript is a language to describe and manipulate binary data formats as types. DataScript consists of two components: a constraint-based specification language that uses DataScript types to describe the physical layout of data and a language binding that provides a simple programming interface to script binary data. A DataScript compiler generates Java libraries that are linked with DataScript scripts. DataScript specifications can be used to describe formats in a programmatic way, eliminating the vagaries and ambiguities often associated with prosaic format descriptions. The libraries generated by the DataScript compiler free the programmer from the tedious task of coding input and output routines. More importantly, they assure correctness and safety by validating both the input read and the output generated. We show examples that demonstrate that DataScript is simple, yet powerful enough to describe many commonly used formats. Similar to how scripting languages such as Perl allow the manipulation of text files, the libraries generated by the DataScript compiler can be used to quickly write scripts that safely manipulate binary files. 1

A dataware house collects and integrates data from multiple, autonomous, heterogeneous, sources. The warehouse effectively maintains one or more materialized views over the source data. In this paper we describe the architecture of the Whips prototype system, which collects, transforms, and integrates data for the warehouse. We show how the required functionality can be divided among cooperating distributed CORBA objects, providing both scalability and the flexibility needed for supporting different application needs and heterogeneous sources. The Whips prototype is a functioning system implemented at Stanford University and we provide preliminary performance results.

Abstract not found