Mapping Aspects to Components

This document defines a representation of aspects in the component model. Such a representation requires modeling the available (primitive) components, defining the composition mechanism, and representing aspects as enhancements of components

Turbomachinery Clearance Control

Controlling interface clearances is the most cost effective method of enhancing turbomachinery performance. Seals control turbomachinery leakages, coolant flows and contribute to overall system rotordynamic stability. In many instances, sealing interfaces and coatings are sacrificial, like lubricants, giving up their integrity for the benefit of the component. They are subjected to abrasion, erosion, oxidation, incursive rubs, foreign object damage (FOD) and deposits as well as extremes in thermal, mechanical, aerodynamic and impact loadings. Tribological pairing of materials control how well and how long these interfaces will be effective in controlling flow. A variety of seal types and materials are required to satisfy turbomachinery sealing demands. These seals must be properly designed to maintain the interface clearances. In some cases, this will mean machining adjacent surfaces, yet in many other applications, coatings are employed for optimum performance. Many seals are coating composites fabricated on superstructures or substrates that are coated with sacrificial materials which can be refurbished either in situ or by removal, stripping, recoating and replacing until substrate life is exceeded. For blade and knife tip sealing an important class of materials known as abradables permit blade or knife rubbing without significant damage or wear to the rotating element while maintaining an effective sealing interface. Most such tip interfaces are passive, yet some, as for the high-pressure turbine (HPT) case or shroud, are actively controlled. This work presents an overview of turbomachinery sealing. Areas covered include: characteristics of gas and steam turbine sealing applications and environments, benefits of sealing, types of standard static and dynamics seals, advanced seal designs, as well as life and limitations issues

Extending Failure Modes and Effects Analysis Approach for Reliability Analysis at the Software Architecture Design Level

Several reliability engineering approaches have been proposed to identify and recover from failures. A well-known and mature approach is the Failure Mode and Effect Analysis (FMEA) method that is usually utilized together with Fault Tree Analysis (FTA) to analyze and diagnose the causes of failures. Unfortunately, both approaches seem to have primarily focused on failures of hardware components and less on software components. Moreover, for utilizing FMEA and FTA very often an existing implementation of the system is required to perform the reliability analysis. We propose extensions to FMEA and FTA to utilize them for the reliability analysis of software at the architecture design level. We present the software architecture reliability analysis approach (SARAH) that incorporates the extended FMEA and FTA. The approach is illustrated using an industrial case for analyzing reliability of the software architecture of a Digital TV

Detecting Mode Inconsistencies in Component-Based Embedded Software

To deal with increasing size and complexity, componentbased software development has been employed in embedded systems. These systems comprise a set of components each of which implements a particular functionality. The system utilizes the components to provide the functionalities that are required in a set of working modes. Components can also be considered to have a set of working modes. They should work in harmony and consistent with the working mode of the system. Due to several errors that remain undetected during the design and implementation phases, components can make wrong assumptions about the working mode of the system and the working modes of the other components. These errors may lead to severe failures. Fault tolerance is required to prevent these failures at runtime. The first step to achieve fault tolerance is error detection. To detect mode inconsistencies at run-time, we propose a "lightweight" error detection mechanism, which can be integrated with component-based embedded systems. We define three dependent levels of abstractions: the run-time behavior of components, the working mode specifications of components and the specification of the working modes of the system. We define explicit links among these levels by specifying a mutual consistency condition. This allows us to detect the user observable run-time errors. The effectiveness of the approach is demonstrated by implementing a software monitor integrated into a TV system

A comparative analysis of software engineering with mature engineering disciplines using a problem solving perspective

Software engineering is compared with traditional engineering disciplines using a domain specific problem-solving model called Problem-Solving for Engineering Model (PSEM). The comparative analysis is performed both from a historical and contemporary view. The historical view provides lessons on the evolution of problem-solving and the maturity of an engineering discipline. The contemporary view provides the current state of engineering disciplines and shows to what extent software development can actually be categorized as an engineering discipline. The results from the comparative analysis show that like mature engineering, software engineering also seems to follow the same path of evolution of problem-solving concepts, but despite promising advances it has not reached yet the level of mature engineering yet. The comparative analysis offers the necessary guidelines for improving software engineering to become a professional mature engineering discipline. © 2011, IGI Global

Feature-based rationale management system for supporting software architecture adaptation

Each software architecture design is the result of a broad set of design decisions and their justifications, that is, the design rationale. Capturing the design rationale is important for a variety of reasons such as enhancing communication, reuse and maintenance. Unfortunately, it appears that there is still a lack of appropriate methods and tools for effectively capturing and managing the architecture design rationale. In this paper we present a feature-based rationale management approach and the corresponding tool environment ArchiRationale for supporting software architecture adaptation. The approach takes as input an existing architecture and captures the design rationale for adapting the architecture for a given quality concern. For this we define a feature model that includes the possible set of architectural tactics to realize the quality concern. The presented approach captures the rationale for deciding on feature selections and for selecting the corresponding architecture design alternatives. ArchiRationale customizes and integrates the Eclipse plugin tools XFeature, ArchStudio and XQuery to provide tool support for capturing, storing and accessing the design rationale. We illustrate the approach for adapting a software architecture for fault tolerance. © 2012 World Scientific Publishing Company