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Software complexity metrics have been studied in the procedural paradigm as a quantitative means of assessing the software development process as well as the quality of software products. Several studies have validated that various metrics are useful indicators of maintenance effort in the procedural paradigm. However, software complexity metrics have rarely been studied in the object oriented paradigm. Very few complexity metrics have been proposed to measure object oriented systems, and the proposed ones have not been validated. This research concentrates on several object oriented software complexity metrics and the validation of these metrics with maintenance effort in two commercial systems. The results of an empirical study of the maintenance activities in the two commercial systems are also described. A metric instrumentation in an object oriented software development framework is presented. / Ph. D.

Polymorphic type abstractions are proposed for constructing concurrent objects and layered peer-to-peer communication protocols, both of which exhibit inherently asynchronous behavior. The type abstractions are shown to be both expressive and efficient in the context of a statically typed object-oriented language. Where appropriate, the utility of the type abstractions is illustrated by demonstrating their usefulness in concurrent programming using the Actor model. The results of this work have direct applicability to problems in concurrent programming, distributed systems, and communication protocol architectures. An extensible, polymorphic type abstraction for structuring concurrent method execution in a strongly typed object-oriented language is introduced. The type abstraction is called a <i>polymorphic lambda type</i>. A lambda type is an abstraction for a procedure that is based in part on λ-abstraction in the λ-calculus. The lambda type is a key component of a concurrent object model that allows methods defined in a class to be instantiated as <i>lambda objects</i>. Lambda objects are used to represent some aspect of behavior and they represent a first-class execution environment. The first-class nature of lambda objects facilitates the construction of more powerful computational abstractions, primarily those requiring 'asynchronous interaction and concurrent execution. Through a series of refinements, lambda objects are shown to be as expressive as traditional procedures with little extra cost for call setup and invocation. Concurrent objects require synchronization control. A type abstraction called a <i>behavior set</i> is introduced for specifying synchronization constraints in a strongly typed concurrent object-oriented language with Actor-style concurrency semantics. The behavior set abstraction offers a solution to structuring synchronization control that coexists with an inheritance mechanism, thereby avoiding the inheritance anomaly. / Ph. D.

Software design within the engineering community has generally been relegated to encoding algorithms for the purpose of executing them very rapidly. This is a very important purpose, however substantially more is required to build an entire CAD application. Structure must be provided to the data maintained in the application. Various analyses must be integrated and coordinated in an orderly fashion. Interaction with the user must be managed. These topics have traditionally received secondary attention. The result has been engineering applications that are difficult to use, costly to create, and expensive to maintain or modify. The system created in this dissertation, the Dynamic Integration System, addresses these issues with respect to engineering-related software. Code constructed with Dynamic Integration System techniques anticipate future needs, such as integration, before those needs explicitly arise. This greatly reduces downstream costs and facilitates the development of engineering-related software. The Dynamic Integration System consists of two primary constructs: Dynamic Variables and dependency hierarchies. Dynamic Variables are used to model the key parameters in an application while a dependency hierarchy is built from the relationships between Dynamic Variables. Using these constructs, issues such as integration and analysis coordination are automated by the underlying Dynamic Integration System facilities. / Ph. D.

This study evaluates three different ways of structuring a software library for an object-oriented system. The traditional class/subclass tree (CIS) is used as well as two methods from the mental model literature: hierarchical cluster analysis (HCA) of sorting data and modal block clustering (MBC) of attribute rating data (Shurtleff, Jenkins, and Sams, 1988; Tullis, 1985). Also examined in this context are two software metrics: depth-in- inheritance-tree (D IT) and response-for-class (RFC) (Lei, 1991, 1993). These two metrics had been found by Lei to correlate with the ease of maintenance of software. It was conjectured that they might also be useful in the study of mental model methods for software. Finally, student and professional programmers are explicitly compared. There has been much debate on the applicability of software-related data generated from student subjects but little research on the topic. The results indicate that subject performance with the MBC representation was worse than with the CIS representation. Also found was that performance with the HCA representation was not sufficiently better to justify the effort involved in creating the new representation. Student programmers were found in this study to be no worse than professional programmers and thus appear to be acceptable substitutes for professional programmers in a class-based search task. This study's results indicate that student response time to locate a class could be used as the lower boundary for professional programmer class locating time. The student error rates, however, could be used as the upper boundary for professional programmer error rate performance in class locating tasks. A "middle" problem was also found. Classes 1n the middle of a library representation proved to be more difficult to locate as measured by time and error rate. Finally, a higher RFC was found to increase search time for a class when it was in the middle of a library representation. A higher RFC also reduced programmer reusability ratings of a class and the programmer's confidence in the reusability rating. / Ph. D.

During the conceptual design phase, aircraft designers require tools to be able to quickly and accurately produce concepts that meet given requirements. These tools often take the form of computer programs and computer-aided design systems which model the shape of the airplane concept and perform various analyses. Often, a common element in these analyses is that only the exterior of the aircraft is considered. Thus a major component of aircraft design is largely overlooked: the internal layout of the airplane. This thesis describes the design and implementation of a new computer software, the Internal Layout Module, designed to enhance the ability of the aircraft designer to arrange, modify, view, and analyze the internal components of an airplane. By considering the internal layout concurrently with the external shape and size, the configurator can effectively design the smallest airplane that meets specifications. The module is coded in C++ entirely under the object-oriented paradigm to ease integration with existing code and to ensure future maintainability and extensibility. New components as varied as seats, galleys, lavatories and cargo containers have been designed for use in the Internal Layout Module and to provide a foundation for future object-oriented geometry for aircraft design. The module has been successfully integrated with the aircraft conceptual design code ACSYNT (AirCraft SYNThesis). The process of adding this new object-oriented module to existing procedural code is discussed in detail. / Master of Science

This work is a numerical study of the 2-D heat equation with Dirichlet boundary conditions over a polygonal domain. The motivation for this study is a chemical vapor deposition (CVD) reactor in which a substrate is heated while being exposed to a gas containing precursor molecules. The interaction between the gas and the substrate results in the deposition of a compound thin film on the substrate. Two different numerical approximations are implemented to produce numerical solutions describing the conduction of thermal energy in the reactor. The first method used is a Crank-Nicholson finite difference technique which tranforms the 2-D heat equation into an algebraic system of equations. For the second method, a semi-discrete method is used which transforms the partial differential equation into a system of ordinary differential equations. The goal of this work is to investigate the influence of boundary conditions, domain geometry, and initial condition on thermal conduction throughout the reactor. Once insight is gained with respect to the aforementioned conditions, optimal design and control can be investigated. This work represents a first step in our long term goal of developing optimal design and control of such CVD systems. This work has been funded through Partnerships in Research Excellence and Transition (PRET) grant number F49620-96-1-0329. / Master of Science

Power failure of pumps, sudden valve actions, and the operation of automatic control systems are all capable of generating high pressure waves in domestic water supply systems. These transient conditions resulting in high pressures can cause pipe failures by damaging valves and fittings. In this study, basic equations for solving transient analysis problems are derived using method of characteristics. Two example problems are presented. One, a single pipe system which is solved by developing an excel spreadsheet. Second, a pipe network problem is solved using transient analysis program called TRANSNET. A transient analysis program is developed in Java. This program can handle suddenly-closing valves, gradually-closing valves, pump power failures and sudden demand changes at junctions. A maximum of four pipes can be present at a junction. A pipe network problem is solved using this java program and the results were found to be similar to that obtained from TRANSNET program. The code can be further extended, for example by developing java applets and graphical user interphase to make it more user friendly. A two dimensional (2D) numerical model is developed using MATLAB to analyze gaseous cavitation in a single pipe system. The model is based on mathematical formulations proposed by Cannizzaro and Pezzinga (2005) and Pezzinga (2003). The model considers gaseous cavitation due to both thermic exhange between gas bubbles and surrounding liquid and during the process of gas release. The results from the model show that during transients, there is significant increase in fluid temperature along with high pressures. In literature pipe failures and noise problems in premise plumbing are atributed to gaseous cavitation. / Master of Science

This thesis discusses the creation of an object-oriented method to facilitate the creation and specification of aircraft mission profiles. Mission profiles are detailed descriptions of an aircraft's flight path and its inflight mission activities. They are a vital aspect of the conceptual design process of an aircraft. The Mission Profile Input System (MPIS) created is general in nature and can be customized to be compatible with existing aircraft CAD systems. All data associated with the mission—phase parameters, phases, and mission parameters, are defined to be objects. Each data type can therefore be customized individually to meet any requirements which may be necessary to make the MPIS compatible with a host system. Customization of the MPIS is further enhanced by the nature of the design upon which it is based. An object-oriented design provides the system with a high degree of extendibility. The encapsulation and inheritance features of object-oriented design allow new types of phases and phase parameters to be simply "plugged" into the existing system. The MPIS provides the user with an interactive, Motif-like interface which is conducive to manipulating the large quantities of data inherent in specifying mission profiles. The system is based on the ISO graphics standard, PHIGS, and hence is device-independent. Moreover, the system has been implemented using the hybrid object-oriented language, C++, which is supported by a large number of computer systems. / Master of Science

With the advancements in the fields of Computer Aided Design (CAD) and Artificial Intelligence (AI), a number of CAD systems that are developed have built-in expert systems to aid the designer in the design process. Recently there has been a trend in industries and research organizations to custom create CAD software to satisfy specific in-house needs. But there are not enough tools available to custom create expert systems to meet the needs of CAD. Expert systems currently have to be developed from basics using languages that are not in everyday use by the CAD programmers. Expert system shells available in the market do not have the flexibility or portability to support the creation of an expert system for multi-disciplinary parametric design. Thus there is a lack of repeatable use software to support the creation of customized expert systems to meet the special needs of parametric design in CAD. In this thesis, the design of an object oriented framework which will aid in the creation of customized expert systems for CAD applications is presented. This framework, known as the Expert Consultation Environment, provides the CAD programmer with tools to create the expert system. This framework consists of various object-oriented classes which the programmer could use. The central part of this framework is the Expert Technician (ET) class. This class represents an expert in a real world situation. Each expert created by the programmer would have its own methods and knowledge in a domain of design. The ET would thus assist the designer using the expert system in that particular domain. The ET would be able to interact with the user in several different modes. These modes are the Consultant, the Transactor, the Observer, the Teacher and the Student modes. The method of interaction between the designer and the ET depends on the mode of operation of the ET. A programmer of the expert system would be able to create these experts by providing knowledge and the design parameters to the ETs. In the case of a multi-disciplinary design the programmer would provide each ET with the knowledge regarding the specific domain of the design. In the case of concurrent engineering, each ET would be provided with knowledge regarding the domain involved in the product cycle of a component. The object-oriented design for the framework has been discussed in detail including class descriptions of all the classes in the framework. A prototype of the framework was developed using C++. The creation of an expert system using this prototype for a multi-disciplinary design application is also discussed in this thesis. / Master of Science