Three Discussions on Object-Oriented Typing

This paper summarizes three discussions conducted at the ECOOP'91 W5 Workshop on ''Types, Inheritance, and Assignments'' Tuesday July 16, 1991 in Geneva, Switzerland, organized by the authors. The three discussions were entitled ''Classes versus Types'', ''Static versus Dynamic Typing'', and ''Type Inference''. All these topics were assumed to be volatile and controversial; indeed, a broad range of diverging opinions were represented. However, much superficial disagreement seemed to be rooted in confusions about terminology. When such issues were resolved, there appeared a consensus about basic definitions and the - often incompatible - choices that one is at liberty to make. This clarification, which we hope to have described below, was the most important achievement of the workshop

New IR & Ranking Algorithm for Top-K Keyword Search on Relational Databases ‘Smart Search’

Database management systems are as old as computers, and the continuous research and development in databases is huge and an interest of many database venders and researchers, as many researchers work in solving and developing new modules and frameworks for more efficient and effective information retrieval based on free form search by users with no knowledge of the structure of the database. Our work as an extension to previous works, introduces new algorithms and components to existing databases to enable the user to search for keywords with high performance and effective top-k results. Work intervention aims at introducing new table structure for indexing of keywords, which would help algorithms to understand the semantics of keywords and generate only the correct CN‟s (Candidate Networks) for fast retrieval of information with ranking of results according to user‟s history, semantics of keywords, distance between keywords and match of keywords. In which a three modules where developed for this purpose. We implemented our three proposed modules and created the necessary tables, with the development of a web search interface called „Smart Search‟ to test our work with different users. The interface records all user interaction with our „Smart Search‟ for analyses, as the analyses of results shows improvements in performance and effective results returned to the user. We conducted hundreds of randomly generated search terms with different sizes and multiple users; all results recorded and analyzed by the system were based on different factors and parameters. We also compared our results with previous work done by other researchers on the DBLP database which we used in our research. Our final result analysis shows the importance of introducing new components to the database for top-k keywords search and the performance of our proposed system with high effective results.نظم إدارة قواعد البيانات قديمة مثل أجيزة الكمبيوتر، و البحث والتطوير المستمر في قواعد بيانات ضخم و ىنالك اىتمام من العديد من مطوري قواعد البيانات والباحثين، كما يعمل العديد من الباحثين في حل وتطوير وحدات جديدة و أطر السترجاع المعمومات بطرق أكثر كفاءة وفعالية عمى أساس نموذج البحث الغير مقيد من قبل المستخدمين الذين ليس لدييم معرفة في بنية قاعدة البيانات. ويأتي عممنا امتدادا لألعمال السابقة، ويدخل الخوارزميات و مكونات جديدة لقواعد البيانات الموجودة لتمكين المستخدم من البحث عن الكممات المفتاحية )search Keyword )مع األداء العالي و نتائج فعالة في الحصول عمى أعمى ترتيب لمبيانات .)Top-K( وييدف ىذا العمل إلى تقديم بنية جديدة لفيرسة الكممات المفتاحية )Table Keywords Index ،)والتي من شأنيا أن تساعد الخوارزميات المقدمة في ىذا البحث لفيم معاني الكممات المفتاحية المدخمة من قبل المستخدم وتوليد فقط الشبكات المرشحة (s’CN (الصحيحة السترجاع سريع لممعمومات مع ترتيب النتائج وفقا ألوزان مختمفة مثل تاريخ البحث لممستخدم، ترتيب الكمات المفتاحية في النتائج والبعد بين الكممات المفتاحية في النتائج بالنسبة لما قام المستخدم بأدخالو. قمنا بأقتراح ثالث مكونات جديدة )Modules )وتنفيذىا من خالل ىذه االطروحة، مع تطوير واجية البحث عمى شبكة اإلنترنت تسمى "البحث الذكي" الختبار عممنا مع المستخدمين. وتتضمن واجية البحث مكونات تسجل تفاعل المستخدمين وتجميع تمك التفاعالت لمتحميل والمقارنة، وتحميالت النتائج تظير تحسينات في أداء استرجاع البينات و النتائج ذات صمة ودقة أعمى. أجرينا مئات عمميات البحث بأستخدام جمل بحث تم أنشائيا بشكل عشوائي من مختمف األحجام، باالضافة الى االستعانة بعدد من المستخدمين ليذه الغاية. واستندت جميع النتائج المسجمة وتحميميا بواسطة واجية البحث عمى عوامل و معايير مختمفة .وقمنا بالنياية بعمل مقارنة لنتائجنا مع االعمال السابقة التي قام بيا باحثون آخرون عمى نفس قاعدة البيانات (DBLP (الشييرة التي استخدمناىا في أطروحتنا. وتظير نتائجنا النيائية مدى أىمية أدخال بنية جديدة لفيرسة الكممات المفتاحية الى قواعد البيانات العالئقية، وبناء خوارزميات استنادا الى تمك الفيرسة لمبحث بأستخدام كممات مفتاحية فقط والحصول عمى نتائج أفضل ودقة أعمى، أضافة الى التحسن في وقت البحث

Provably Correct Compiler Generation

We have designed, implemented, and proved the correctness of a compiler generator that accepts action semantic descriptions of imperative programming languages. We have used it to generate compilers for both a toy language and a non-trivial subset of Ada. The generated compilers emit absolute code for an abstract RISC machine language that is assembled into code for the SPARC and the HP Precision Architecture. The generated code is an order of magnitude better than that produced by compilers generated by the classical systems of Mosses, Paulson, and Wand. Our machine language needs no run time type-checking and is thus more realistic than those considered in previous compiler proofs. We use solely algebraic specifications; proofs are given in the initiaI model. The use of action semantics makes the processable language specifications easy to read and pleasant to work with. We view our compiler generator as a promising first step towards user-friendly and automatic generation of realistic and provably correct compilers

Dynamic Upgrade of Distributed Software Components

Die Aktualisierung von komplexen Telekommunikationssystemen, die sich durch die ihnen eigene Verteiltheit und hohe Kosten bei System-Nichtverfügbarkeit auszeichnen, ist ein komplizierter und fehleranfälliger Wartungsprozess. Noch stärkere Herausforderungen bergen solche Software-Aktualisierungen, die die Systemverfügbarkeit nicht beeinträchtigen sollen. Dynamic Upgrade ist eine Wartungstechnik, die das Verwalten und die Durchführung von Software-Aktualisierung automatisiert und damit den Betrieb des Systems während der Wartungszeit nicht unterbricht. In dieser Arbeit wird das Dynamic Upgrade als ein Sonderfall der Bereitstellung und Inbetriebnahme (Deployment) von Software betrachtet, in dem Teile der einen Dienst repräsentierenden Software durch neue Versionen im laufenden Betrieb ersetzt werden. Die Problemstellung des Dynamic Upgrade wird anhand einer vom Autor erarbeiteten Taxonomie erläutert, die die Entwurfsmöglichkeiten für ein System zur Unterstützung von Dynamic Upgrade hinsichtlich dreier Systemaspekte klassifiziert: Deployment, Evolution und Zuverlässigkeit (Dependability). Mit Hilfe dieser Taxonomie lassen sich auch andere Systeme zur Unterstützung von Dynamic Upgrade miteinander vergleichen. Aufbauend auf einem ausführlichen Vergleich über existierende Ansätze zur Unterstützung von Dynamic Upgrade, wird in der vorliegenden Arbeit eine Lösung entwickelt und dargestellt, die Dynamic Upgrade in verteilten komponentenbasierten Software-Systemen ermöglicht. Ausgehend von der Problemanalyse wird mit Hilfe des Unified Process ein als Deployment and Upgrade Facility bezeichnetes Modell entwickelt, das sowohl die benötigten Leistungsfähigkeiten eines Dynamic Upgrade unterstützenden Systems als auch Eigenschaften von aktualisierbaren Software-Komponenten beschreibt. Dieses Modell ist Plattform-unabhängig und einsetzbar für mehrere unterliegende Middleware-Technologien. Das Modell wird in einem Java-basierten prototypischen Rahmenwerk programmiert und um plattformspezifische Mechanismen auf der Jgroup/ARM Middleware erweitert. Das Rahmenwerk umfasst allgemeine Entwurfslösungen und ?muster, die sich für die Konstruktion einer Unterstützung für Dynamic Upgrade eignen. Es erlaubt die Kontrolle der Lebenszyklen von Aktualisierungsprozessen und ihre Koordination im Zielsystem. Darüber hinaus definiert es eine Reihe von Unterstützungsmechanismen und Algorithmen für den dynamischen Aktualisierungsprozess, der gegebenenfalls mit unterschiedlichen Zielsetzungen und unter verschiedenen Randbedingungen erfolgen soll. Insbesondere wird ein Aktualisierungsalgorithmus für replizierte Software-Komponenten dargestellt. Das entwickelte Rahmenwerk wird zwecks Plausibilitätsprüfung der dargestellten Ansätze und zur Auswertung der Auswirkungen der Dynamic Upgrade unterstützenden Mechanismen im Hinblick auf Systemperformanz in mehreren Experimenten eingesetzt. Diese quantitative Evaluierung der Experimente führt zu einer Spezifikationen eines einfachen Bewertungsmaßstabs (Benchmark), der sich zum Vergleich von Dynamic Upgrade unterstützenden Systemen eignet.Upgrading complex telecommunication software systems, characterized by their inherent distribution and a very high cost of system unavailability, is a difficult and error-prone maintenance activity. Even more challenging are such software upgrades that do not compromise the system availability. Dynamic upgrades is a technique, which automates performing and managing upgrades so that the software system remains operational during the upgrade time. In this thesis, the dynamic upgrade is considered as a special case of software deployment, in which a running service has to be replaced with its new version. The problems of dynamic upgrades are introduced using a novel taxonomy that classifies the design issues to be solved when building support for dynamic upgrade with regard to three system aspects: deployment, evolution and dependability and provides a reference to comparing other systems supporting dynamic upgrades. An extensive and thorough survey of existing approaches to dynamic upgrades follows and, furthermore, is as a starting point to designing a solution supporting dynamic upgrades in distributed component-based software systems. Derived from the problem analysis, a model called Deployment and Upgrade Facility describing the capabilities needed for managing and performing dynamic upgrades as well as properties of upgradable software components is developed using the Unified Process approach. The model is platform independent and can be used with a range of underlying middleware technologies. The model is implemented in a Java-based prototypical framework and extended with platform specific mechanisms on top of the JGroup/ARM middleware. The framework captures common design solutions and patterns for building a support for dynamic upgrade. The framework allows for controlling life-cycle and coordination of upgrade processes in the system. It also defines a number of supporting mechanisms and algorithms for the upgrade process. A special attention is drawn to an upgrade algorithm for replicated software components for achieving a synergy of replication techniques and dynamic upgrade . The developed framework is used to validate the feasibility of the approach and to measure the overhead of the mechanisms supporting dynamic upgrade with regard to the performance of the system being upgraded in a number of practical experiments. This quantitative evaluation of the experiments leads to a specification of a simple benchmark for systems supporting dynamic upgrades

Three Discussions on Object-Oriented Typing

This paper summarizes three discussions conducted at the ECOOP'91 W5 Workshop on "Types, Inheritance, and Assignments" Tuesday July 16, 1991 in Geneva, Switzerland, organized by the authors. Participants at the workshop were: Birger Andersen, Andrew Black, Gregor Bochmann, Gilad Bracha, Simon Brock, Brian Brown, David Carrington, Bruce Conrad, Elspeth Cusack, Jeremy Dick, Rainer Fischbach, Elio Giovanetti, Andreas Hense, John Hogg, Rick Holt, Urs Holzle, Norm Hutchinson, Eric Jul, Jørgen Lindskov Knudsen, Christian Laasch, Serge Lacourte, Doug Lea, Karl Lieberherr, Ole Lehrmann Madsen, Boris Magnusson, Rick Mugridge, Birger Møller-Pedersen, Jens Palsberg, Oskar Permvall, Markku Sakkinen, Michael I. Schwartzbach, Alan Snyder, Clemens Szyperski, Andrew Watson, and Alan Wills. Most participants contributed a short position paper; they are collected in [1] The three discussions were entitled "Classes versus Types", "Static versus Dynamic Typing", and "Type Inference". All these topics were assumed to be volatile and controversial; indeed, a broad range of diverging opinions were represented. However, much superficial disagreement seemed to be rooted in confusions about terminology. When such issues were resolved, there appeared a consensus about basic definitions and the---often incompatible---choices that one is at liberty to make. This clarification, which we hope to have described below, was the most important achievement of the workshop. In our summary we have attempted to organize the topics and arguments into a succinct and readable format. In particular, we sometimes emphasize points of agreement or divergence that were only implied at the workshop. We hope that this style will result in a coherent overview of this research area within the available space. Similar ..