gbeta - a Language with Virtual Attributes, Block Structure, and Propagating, Dynamic Inheritance

A language design development process is presented which leads to a language, gbeta, with a tight integration of virtual classes, general block structure, and a multiple inheritance mechanism based on coarse-grained structural type equivalence. From this emerges the concept of propagating specialization. The power lies in the fact that a simple expression can have far-reaching but well-organized consequences, e.g., in one step causing the combination of families of classes, then by propagation the members of those families, and finally by propagation the methods of the members. Moreover, classes are first class values which can be constructed at run-time, and it is possible to inherit from classes whether or not they are compile-time constants, and whether or not they were created dynamically. It is also possible to change the class and structure of an existing object at run-time, preserving object identity. Even though such dynamism is normally not seen in statically type-checked languages, these constructs have been integrated without compromising the static type safety of the language

Collected software engineering papers, volume 12

This document is a collection of selected technical papers produced by participants in the Software Engineering Laboratory (SEL) from November 1993 through October 1994. The purpose of the document is to make available, in one reference, some results of SEL research that originally appeared in a number of different forums. This is the 12th such volume of technical papers produced by the SEL. Although these papers cover several topics related to software engineering, they do not encompass the entire scope of SEL activities and interests. Additional information about the SEL and its research efforts may be obtained from the sources listed in the bibliography at the end of this document

Proceedings of Monterey Workshop 2001 Engineering Automation for Sofware Intensive System Integration

The 2001 Monterey Workshop on Engineering Automation for Software Intensive System Integration was sponsored by the Office of Naval Research, Air Force Office of Scientific Research, Army Research Office and the Defense Advance Research Projects Agency. It is our pleasure to thank the workshop advisory and sponsors for their vision of a principled engineering solution for software and for their many-year tireless effort in supporting a series of workshops to bring everyone together.This workshop is the 8 in a series of International workshops. The workshop was held in Monterey Beach Hotel, Monterey, California during June 18-22, 2001. The general theme of the workshop has been to present and discuss research works that aims at increasing the practical impact of formal methods for software and systems engineering. The particular focus of this workshop was "Engineering Automation for Software Intensive System Integration". Previous workshops have been focused on issues including, "Real-time & Concurrent Systems", "Software Merging and Slicing", "Software Evolution", "Software Architecture", "Requirements Targeting Software" and "Modeling Software System Structures in a fastly moving scenario".Office of Naval ResearchAir Force Office of Scientific Research Army Research OfficeDefense Advanced Research Projects AgencyApproved for public release, distribution unlimite

Simulating sensorimotor systems with cortical topology

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references.Not availabl

Dynamic encapsulation of C++ objects

Classes in C++ provide static encapsulation of objects, by generating code which contains specific knowledge about the internals of encapsulated objects. Static encapsulation occurs at compile time, and therefore cannot directly support the evolution of objects, since recompilation of source code is required if the internal layout changes. This also prohibits the use of distributed or persistent objects without first ensuring that the internal representations of the objects match the ones in the compiled code. Dynamic encapsulation occurs at run-time, and allows the compiled code to exist without the knowledge of any particular object representation. Abstract base classes with C++ virtual functions support a limited form of dynamic encapsulation, but only for objects originally designated to inherit from those classes. Some languages, such as Smalltalk, support dynamic encapsulation, but with significantly less performance than statically encapsulated languages. An object model using dynamic type-binding is presented which allows the flexibility of dynamic encapsulation with much of the efficiency of static encapsulation. With this model, objects can potentially communicate and migrate across address space and network boundaries without specific prior knowledge of representations, and can invoke functions on local objects with no more run-time overhead than standard C++ virtual function calls. This dynamic encapsulation model is incorporated into DC++, a C++-based language with extensions that allow for the dynamic encapsulation of existing C++ objects, and DECO (the Dynamic Encapsulator of C++ Objects), a utility for converting DC++ source code into C++

Integrating measurement techniques in an Object-Orientedsystems design process.

The theme of this thesis is the assessment of quality in class hierarchies. In particular, the notion ofinheritance and the mechanism of redefinition from a modelling perspective are reviewed. It isshown that, in Object-Oriented languages, controversial uses of inheritance can be implementedand are subject of debate as they contradict the essence of inheritance. The discovery of anunexpected use of the method redefinition mechanism confirmed that potential designinconsistencies occur more often than expected in class hierarchies. To address such problems,design heuristics and measurement techniques are investigated as the main instrument tools for theevaluation "goodness" or "badness" in class hierarchies. Their benefits are demonstrated withinthe design process. After the identification of an obscure use of the method redefinition mechanism referred to as themultiple descendant redefinition (MDR) problem, a set of metrics based on the GQMlMEDEA[Bri&aI94] model is proposed. To enable a measurement programme to take place within a designprocess, the necessary design considerations are detailed and the technical issues involved in themeasurement process are presented. Both aspects form ~. methodological approach for classhierarchy assessment and especially concentrate on the use of the redefinition mechanism.. .As one of the main criticisms of the measure~ent science is the lack orgood design feedback, the, analysis and interpretation phase. of the metfics results is seen: as a crucial phase for inferring,meaningful conclusions. A novel· data interpretation framework is pr~posed' and includes the use ofvarious graphical data representations and detection techniques. Also, the notion of redefinitionprofiles suggested a, more generic approach whereby a pattern profile can be found for a metric.The benefits of the data interpretation method for the extraction of meaningful design feedbackfrom the metrics results are discussed.The implementation of a metric tool collector enabled a set of experiments to be carried out on theSmalltalk class hierarchy. Surprisingly, the analysis of metrics results showed that methodredefmition is heavily used compared to method extension. This suggested the existence ofpotential design inconsistencies in the class hierarchy and permitted the discovery of the MDRproblem on many occasions. In addition, a set of experiments demonstrates the benefits of examplegraphical representations together with detection techniques such as alarmers. In the light offacilitating the interpretation phase, the need for additional supporting tools is highlighted. This thesis illustrates the potential benefits of integration of measurement techniques within anObject-Oriented design process. Given the identification of the MDR problem, it is believed thatthe redefinition metrics are strong and simple candidates for detecting complex design problemsoccurring within a class hierarchy. An integrated design assessment model is proposed whichlogically fits into an incremental design development process. Benefits and disadvantages of theapproach are discussed together with future work

Converting Java programs to use generic libraries

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (leaves 121-127).Java 1.5 will include a type system (called JSR-14) that supports parametric polymorphism, or generic classes. This will bring many benefits to Java programmers, not least because current Java practise makes heavy use of logically-generic classes, including container classes. Translation of Java source code into semantically equivalent JSR-14 source code requires two steps: parameterisation (adding type parameters to class definitions) and instantiation (adding the type arguments at each use of a parameterised class). Parameterisation need be done only once for a class, whereas instantiation must be performed for each client, of which there are potentially many more. Therefore, this work focuses on the instantiation problem. We present a technique to determine sound and precise JSR-14 types at each use of a class for which a generic type specification is available. Our approach uses a precise and context-sensitive pointer analysis to determine possible types at allocation sites, and a set-constraint-based analysis (that incorporates guarded, or conditional, constraints) to choose consistent types for both allocation and declaration sites. The technique safely handles all features of the JSR-14 type system, notably the raw types (which provide backward compatibility) and 'unchecked' operations on them. We have implemented our analysis in a tool that automatically inserts type arguments into Java code, and we report its performance when applied to a number of real-world Java programs.by Alan A.A. Donovan.S.M

Selective transparency in distributed transaction processing

PhD ThesisObject-oriented programming languages provide a powerful interface for programmers to access the mechanisms necessary for reliable distributed computing. Using inheritance and polymorphism provided by the object model, it is possible to develop a hierarchy of classes to capture the semantics and inter-relationships of various levels of functionality required for distributed transaction processing. Using multiple inheritance, application developers can selectively apply transaction properties to suit the requirements of the application objects. In addition to the specific problems of (distributed) transaction processing in an environment of persistent objects, there is a need for a unified framework, or architecture in which to place this system. To be truly effective, not only the transaction manager, but the entire transaction support environment must be described, designed and implemented in terms of objects. This thesis presents an architecture for reliable distributed processing in which the management of persistence, provision of transaction properties (e.g., concurrency control), and organisation of support services (e.g., RPC) are all gathered into a unified design based on the object model.UK Science and Engineering Council: ESPRIT project