Raimund K. Ege

Logical composition of object-oriented interfaces

This paper describes an approach to object-oriented interface design that goes beyond mere object decomposition. In our user interface management system we use logic and filters to declaratively specify and control a space of ways that objects may be composed to create interfaces. A filter is a package of constraints and associated typed objects that express the relationship of data and representation objects. Conceptually our system is completely based on constraints. Filters provide the high bandwidth constraints to maintain the components of the direct-manipulation interface while the logic forms the low bandwidth constraints to combine and provide communication between these components. The use of Horn-clause logic to compose separate interface objects facilitates both the distribution of computation onto multiple processors and the generation of multiple views of data. Intelligent backtracking implemented in the logic allows for user- and system-initiated undo operations to correct errors and/or try alternative approaches to a problem. We illustrate the power and flexibility of this approach by describing a floor layout and design system.

Mediation security specification and enforcement for heterogeneous databases

Information sharing among heterogeneous databases requires increasing attention and poses a pressing need. Successful protection of information by an effective access control mechanism is a basic requirement for interoperation among heterogeneous data sources. However, most existing work on access control focuses on access control model and security related information, little effort is devoted to exploring access control on the semantic-related heterogeneous databases. No current work resolves the security challenges faced by heterogeneous databases, i.e., context-aware authorization, semantic heterogeneity of databases and policy specification at different points. This paper proposes a mediation security system that secures the information sharing among heterogeneous databases with the promise to meet the above requirements. The proposed system models the flexible access control requirements specific to mediation security while providing uniform access for heterogeneous data sources.

Object-oriented user interfaces

The typical overall organization of an object-oriented user interface is shown and its layered relationship with the application is explained. Typical classes and their hierarchies in the presentation (output), input, and control components are illustrated, such as classes for graphical objects: windows, menus, icons, mouses, keyboards. The chapter explains how object-oriented concepts improve user interfaces: (1) by allowing flexible construction and dynamic behavior in a uniform programming framework, (2) by producing reusable and extensible components, and (3) by achieving multiple levels of device and platform independence. The Smalltalk MVC paradigm and the C++ Interviews toolkit are described.

Mediation framework modeling and verification by SAM

The architecture-level design of mediation systems requires rigorous modeling and analysis techniques to assure the correctness the behaviors of the architecture. The Software Architecture Model (SAM) is a formal systematic software architecture specification and analysis methodology that is able to define and analyze different system aspects using different formalisms to improve understandability and reduce complexity. This paper proposes an adaptive mediation framework that provides an easily extensible, decentralized environment for sharing data from heterogeneous databases. We demonstrate how to apply SAM to specify the mediation architecture and analyze the temporal properties of the proposed architecture.

Object-Oriented Programming Languages

This chapter surveys the major object-oriented programming languages. It begins with an overview of the features that are expected in these languages and then discusses Smalltalk, Objective-C, Eiffel, and an object-oriented version of Pascal in detail. Each of these languages has its own distinct style of syntax and its own interpretation and implementation of the basic concepts. For each language, examples illustrate the basic and special features. The examples are drawn from the course scheduling application discussed in Chapter 5.

The Object-Oriented Model of Computation

The basic notion presented in this chapter is message passing. It is compared to the traditional procedure (function) call. Message passing and method lookup represent the binding of a procedure name to a procedure body. Examples illustrate this central notion with object diagrams and C++ code. Other critical terms, such as static and dynamic binding and overloading, are introduced, illustrated, and compared.

Object-Oriented Design

The application of object-oriented technology to programming calls for new techniques in software design. This chapter discusses object-oriented design. Object-oriented design techniques deal with how to best identify entities in the problem domain that can be mapped into objects and classes of objects. An important issue is how to identify objects and classes in an application problem, and how to make use of existing classes to gain the highest productivity.

Chapter 1 – Basic Concepts

Starting out with the familiar “hello world” program example, this chapter transforms the example into an object method, thereby introducing the notions of object and method. It also serves as an initial introduction to the object diagrams and to the C++ syntax. The importance of object identity is illustrated. More examples follow, introducing the notions of object structure, captured by instance variables. The need to describe groups of objects, instead of single objects, introduces the notion of class. How to create objects from classes is explained and illustrated. A first taste of other programming languages is given with a discussion of how they use slightly different terms for the same basic concepts.

Object-Oriented Databases

Object orientation can also be applied to database technology. An object-oriented database management system differs from an object-oriented programming language in that its focus is on efficient management of a large amount of data and on providing for data access and manipulation. The typical overall organization of an object-oriented database and its relationship to the application is explained in this chapter. The classes that are defined for such a database reflect the classes that exist in the application. Examples illustrate how to benefit from the persistent storage of objects offered by the database that also offers database-specific features such as handling of transactions, data access authorization, locking, and concurrency. The state of the art in commercially available object-oriented database systems is discussed.

The Object-Oriented Advantage

How useful is object-oriented programming? The second part of this book is starting out with a discussion of software engineering principles, such as abstraction and modularity, information hiding and encapsulation, and their potential to increase software productivity and reuse. The chapter explains how object-oriented concepts improve the software engineering process. Several examples illustrate the improvement in quality and productivity.