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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 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

The use of the object oriented programming approach in developing applications for the analysis and design of reinforced concrete structures is discussed. Two object oriented programming languages, Actor and Borland C++ for Windows were used to develop several applications. Actor is a pure object oriented programming language while C++ is a hybrid object oriented programming language. A simple program for computing the flexural capacity of reinforced concrete tee beams was developed in both languages. A second program for the analysis and design of reinforced concrete continuous beams was developed in Actor and C++. This application is representative of a practical structural engineering application and has both analysis and design components. The procedures and techniques used in the development of this application can easily be applied to the development of other structural engineering applications. A third program for the design of simply supported beams was also developed in Actor. The advantages and disadvantages of object oriented programming for structural engineering application development were studied. It was found that object oriented programming has significant benefits. However, these benefits can only be utilized if careful thought is given during the program development stage. There is also some overhead associated with object oriented programming. A comparative study of the two programming languages: Actor and Borland C++ was also performed. / Master of Science

This thesis discusses the research and development of a program to aid the aircraft designer with determining the pilot's visual acuity. The discussion involves the use of Object-Oriented programming, the use of a graphical user interface based upon the graphics standard PHIGS (Programmers Hierarchical interactive Graphics System) and the integration of this Pilot's View Module with an existing aircraft CAD (Computer Aided Design) program known as ACSYNT. The result is a program that lends itself to reuse and easy modification and is device independent. The main purpose of the pilot's view module is to provide total vision plots for the pilot in accordance with the military standards as stated in the document 850B. These standards include visibility design goals for several types of aircraft as well as methods for calculating and presenting the vision plots. The integration of the pilots view module with ACSYNT affords the designer the ability to examine the trade-offs associated with a particular cockpit design and the performance of that design within one CAD program. / Master of Science