Theory and Practice of Transactional Method Caching

Nowadays, tiered architectures are widely accepted for constructing large scale information systems. In this context application servers often form the bottleneck for a system's efficiency. An application server exposes an object oriented interface consisting of set of methods which are accessed by potentially remote clients. The idea of method caching is to store results of read-only method invocations with respect to the application server's interface on the client side. If the client invokes the same method with the same arguments again, the corresponding result can be taken from the cache without contacting the server. It has been shown that this approach can considerably improve a real world system's efficiency. This paper extends the concept of method caching by addressing the case where clients wrap related method invocations in ACID transactions. Demarcating sequences of method calls in this way is supported by many important application server standards. In this context the paper presents an architecture, a theory and an efficient protocol for maintaining full transactional consistency and in particular serializability when using a method cache on the client side. In order to create a protocol for scheduling cached method results, the paper extends a classical transaction formalism. Based on this extension, a recovery protocol and an optimistic serializability protocol are derived. The latter one differs from traditional transactional cache protocols in many essential ways. An efficiency experiment validates the approach: Using the cache a system's performance and scalability are considerably improved

Das Fremde sehen: der europäische Blick auf Japan in der künstlerischen Dokumentarfotografie

Das Fremde: Klischees und Stereotype beeinflussen seine Wahrnehmung. Auch dem europäischen Japanbild liegen viele Klischees zu Grunde. Wie kommt es dazu? Das Buch verfolgt die historische Entwicklung dieser Vorstellungen vom faszinierenden Fremden und setzt sie in Beziehung zur (als authentisch geltenden) Dokumentarfotografie. Beispielhaft wird gezeigt, wie zeitgenössische Projekte künstlerischer Dokumentarfotografen diese Bildklischees auszuhebeln versuchen, um so ein neues, kulturell fremdes Japan zu zeigen

Temporized and localized rule sets

Constraint management plays an important role in design applications where constraints reect design restrictions and design decisions. ECA rules are a widely used mechanism to enforce constraints. The paper argues that such rules must be augmented for design environments by a spatial and a temporal dimension of validity, resulting in so-called area-event-condition-action (AECA) rules. The spatial dimension allows to restrict constraints locally in the design space, and to control interaction between designers. The temporal dimension permits designers to retract their designs to earlier stages. The paper introduces the concept of AECA rules, motivates them by examples from building design, discusses rule management, and then introduces two important issues, conflict detection during collaboration, and backtracking during design revision

From the Periphery. A Photographic Approach to the City of Braunschweig, Germany

The paper introduces a photographic approach to the topics of housing projects and automobile –friendliness as perceived in an average German city. The photographic series From the Periphery explores not only multiple layers of peripherization within the urban fabric but also the onlookers’ perspective that differs according to the chosen mode of transportation. Interweaving the underlying photographic concept of artistic documentary –chosen to provide the viewers a specific visuality of urban constellations– with the urban condition and photography theory the paper explores the visual access to specific urban aspects. Taking preliminary decision –making and work on location into account, the paper provides a profound insight into a photographer’s mode of operation within the urban sphere

Das Fremde sehen

Das Fremde: Klischees und Stereotype beeinflussen seine Wahrnehmung. Auch dem europäischen Japanbild liegen viele Klischees zu Grunde. Wie kommt es dazu? Das Buch verfolgt die historische Entwicklung dieser Vorstellungen vom faszinierenden Fremden und setzt sie in Beziehung zur (als authentisch geltenden) Dokumentarfotografie. Beispielhaft wird gezeigt, wie zeitgenössische Projekte künstlerischer Dokumentarfotografen diese Bildklischees auszuhebeln versuchen, um so ein neues, kulturell fremdes Japan zu zeigen

Bereichsdynamische Konsistenzüberwachung

Eine Datenbankunterstützung des integrierten architektonischen Entwurfes stellt mannigfaltige Anforderungen, die von heutigen Datenbanksystemen nicht erfüllt werden können. Insbesondere die Überwachung von Constraints stellt hier eine große Herausforderung dar. Dieser Bericht hat zum Ziel, zunächst die Anforderungen an einen Mechanismus zur Überwachung der Constraints auszuarbeiten und anschließend ein Konzept vorzustellen, das in der Lage ist diese Anforderungen zu erfüllen