MELDing Multiple Granularities of Parallelism

We are developing an experimental programming language, MELD, that supports a range of concurrent styles by supporting multiple programming paradigms at multiple levels of granularity. MELD integrates three granularities of parallelism: macro dataflow among statements within a method or among methods for fine grain concurrency, synchronous or asynchronous message passing among local or remote objects for medium grain concurrency, and transactions for large grain concurrency among users

Object-Oriented Programming Language Facilities for Concurrency Control

Concurrent object-oriented programming systems require support for concurrency control, to enforce consistent commitment of changes and to support program-initiated rollback after application-specific failures. We have explored three different concurrency control models -- atomic blocks, serializable transactions, and commit-serializable transactions -- as part of the MELD programming language. We present our designs, discuss certain programming problems and implementation issues, and compare our work on MELD to other concurrent object-based systems

New Inheritance Models That Facilitate Source Code Reuse in Object-oriented Programming

Code reusability is a primary objective in the development of software systems. The object-oriented programming methodology is one of the areas that facilitate the development of software systems by allowing and promoting code reuse and modular designs. Object-oriented programming languages (OOPLs) provide different facilities to attain efficient reuse and reliable extension of existing software components. Inheritance is an important language feature that is conducive to reusability and extensibility. Various OOPLs provide different inheritance models based on different interpretations of the inheritance notion. Therefore, OOPLs have different characteristics derived from their respective inheritance models. This dissertation is concerned with solutions for three major problems that limit the utilization of inheritance for code reusability. The range of object -oriented applications and thus the usage of object-oriented programming in general is also discussed. The three major problems are: 1) the relationship between inheritance and other related issues such as encapsulation, access techniques, visibility of inheritance, and subtyping; 2) the hierarchical structure imposed by inheritance among classes; and 3) the accessibility of previous versions of the modified methods defmed in classes located at higher levels of the inheritance structure than the parent classes. 1be proposed solutions for these problems are presented as new inheritance models that facilitate code reuse and relax the restrictions imposed on inheritance models by languages. A survey and taxonomy of the conventional inheritance models, and a comparison and analysis of some of the common OOPLs are also presented in the dissertation.Computer Scienc

Abstraction over non-local object information in aspect-oriented programming using path expression pointcuts

Aspect-oriented software development (AOSD) consists of a number of technologies that promise a better level of modularization of concerns that cannot be separated in individual modules by using conventional techniques. Aspect-oriented programming (AOP) is one of these technologies. It allows the modularization at the level of software application code. It provides programmers with means to quantify over specific points in the base application code, called join points, at which the crosscutting concern code must be triggered. The quantification is achieved by special selection constructs called pointcuts, while the triggered code that is responsible for adapting the selected join point is provided by special construct called advice. The selection and adaptation mechanisms in aspect-oriented programming depend heavily on the distinguishing properties of the join points. These properties can either be derived from the local execution context at the join point or they are considered to be non-local to the join point. Aspect-oriented systems provide a plenty of pointcut constructs that support accessing the local join point properties, while they rarely support the non-local properties. A large research effort has been achieved to extend current aspectoriented systems in order to solve the problem of non-locality. However, none of these proposals support the non-local object relationships. There are many situations where a good abstraction over nonlocal object information is needed, otherwise, the developers will be obliged to provide complex and error-prone workarounds inside advice body that conceptually do not reflect the semantics of join point selection and mix it with the semantics of join point daptation. Such recurrent situations occur when trying to modularize the object persistence concern. Object persistence, the process of storing and retrieving objects to and from the datastore, is a classical example of crosscutting concern. Orthogonal object persistence meets the obliviousness property of AOP: The base code should not be prepared upfront for persistence. This thesis addresses the shortcomings in current aspect-oriented persistence systems. It shows that the reason for such shortcomings is due to the lack of supporting non-local object information by the used aspect-oriented languages. To overcome this problem, this thesis proposes a new extension to the current pointcut languages called path expression pointcuts that operate on object graphs and make relevant object information available to the aspects. As an explicit and complete construct, a formal semantics and type system have provided. Moreover, an implementation of path expression pointcuts is discussed in the thesis along with its usage to show how the aforementioned problems are resolved