Frank Lauterwald

Semantics of a runtime adaptable transaction manager

Database Management Systems (DBMSs) that can be tailored to specific requirements offer the potential to improve reliability and maintainability and simultaneously the ability to reduce the footprint of the code base. If the requirements of an application change during runtime the DBMS should be adapted without a shutdown. Runtime-adaptation is a new and promising research direction to dynamically change the behavior of a DBMS. Especially the adaptation of the Transaction Manager (TM) states a challenge. In this paper, we present the session semantics of a runtime-adaptable TM. We define preliminaries and assumptions to activate the TM during sessions from a conceptual point of view. The advantages and disadvanteges of different approaches are discussed, especially regarding the occurence of ANSI SQL phenomena. From a technical point of view, we define requirements for the architecture of the TM and the DBMS that arose in our prototype.

Efficient and cost-aware operator placement in heterogeneous stream-processing environments

Operator placement for distributed stream-processing systems is still a challenging problem that can be modeled as a Task Assignment Problem (TAP). Multiple objectives are relevant for the optimization in heterogeneous stream-processing systems as there are different capabilities of the underlying networks and stream-processing nodes. We present an approach based on linear programming relaxation and iterative deterministic rounding. It uses an efficient linearization approach for the quadratic objective function that results from the TAP.

Integration of dynamic AOP into the OSGi service platform

The ability to adapt to different computing environments or external changes is an important requirement for both stationary and mobile computing. Without this ability, all requirements have to be foreseen, which is often not possible in practice. Classical software engineering approaches often lead to redeployment or even software migration. Therefore loosely coupled software design and a dynamic adaptation model are required. Dynamic aspect-oriented programming (d-AOP) in conjunction with service oriented programming is well suited to face this demand. One well known approach providing a service-oriented component model is the OSGi Service Platform. This paper introduces our approach to combine an OSGi Framework with d-AOP to establish dynamic adaptation of core concerns as well as crosscutting concerns. Seamless integration of current d-AOP frameworks is managed by mapping aspect deployment and undeployment to OSGi bundle lifecycle operations without affecting the deployment model. Unlike former proposals, this approach retains the strict separation of bundles as mandated by OSGi.

An algebra for pattern matching, time-aware aggregates and partitions on relational data streams

Many interesting applications of continuous-query processing are concerned with pattern matching or complex temporal aggregation of events. Real-world queries that rely on these operations are difficult to implement in current stream-processing systems. The reason seems to be a gap between two types of existing query languages: Some languages (e. g. CQL) offer a small set of simple operators that can be combined in order to create complex queries. While these languages provide sound and comprehensible semantics, they lack the expressiveness required for many real-world applications. Other approaches (e. g. Aurora) provide powerful operators but lack semantic strictness, which is required for reasoning about query results. Such reasoning is a prerequisite for safe query optimization. We try to bridge this gap by integrating operators for pattern matching and time-aware aggregates into a general-purpose stream model featuring stream partitioning. These operators can answer several questions that we have found to be relevant in a real-world object-tracking scenario. Moreover, they are formally defined, allowing expressive and efficient queries to be written in CQL-like languages, while remaining understandable and easy to use.

Black-box determination of cost models' parameters for federated stream-processing systems

For distribution and deployment of queries in distributed stream-processing environments, it is vital to estimate the expected costs in advance. Having heterogeneous Stream-Processing Systems (SPSs) running on various hosts, the parameters of a cost model for an operator must be determined by measurements for each relevant combination of an SPS and hardware. This paper presents a black-box method that determines the parameters of appropriate cost models that regard system-specific behavior. For some SPSs, there might not be any appropriate cost model available due to the lack of internal knowledge. If no cost model is available for any reason, we provide and apply a non-parametric model.

The Adaptation Model of a Runtime Adaptable DBMS

Nowadays maintenance of database management systems (DBMSs) often requires offline operations for enhancement of functionality or security updates. This hampers the availability of the provided services and can cause undesirable implications. Therefore it is essential to minimize the downtime of DBMSs. We present the CoBRA DB (Component Based Runtime Adaptable DataBase) project that allows the adaptation and extension of a modular DBMS at runtime. In this paper we focus on the definition of an adaptation model describing the semantics of adaptation processes.

Umgang mit semantischer Heterogenität bei der Integration stromverarbeitender Systeme

ZusammenfassungVerteilte Datenstromverarbeitung unter Beteiligung heterogener Datenstromsysteme und Sensorknoten erfährt zunehmendes Interesse. Ein Problem dabei ist, dass die heute verfügbaren Datenstromsysteme sich hinsichtlich ihrer Verarbeitungslogik unterscheiden. Das zeigt sich darin, dass für vermeintlich gleiche Anfragen unterschiedliche Ergebnisse erzeugt werden bzw. Ergebnisströme unterschiedliches zeitliches Verhalten aufweisen. Problematisch ist das insbesondere für die automatische Integration heterogener Datenstromsysteme im Sinne einer Föderation, denn hier gibt der Anwendungsentwickler die Kontrolle darüber, wie und von welchem System Ergebnisse erzeugt werden, an einen Koordinator ab. Der möglichen Abweichungen muss sich der Anwendungsentwickler bewusst sein und er muss angeben können, welche davon er in Kauf nehmen will. Dieser Beitrag beschreibt einen Ansatz, der es dem Anwendungsentwickler wahlweise erlaubt, präzise zu definieren, wie eine Anfrage verarbeitet werden soll oder dem System bestimmte Teilaspekte freizustellen, um so Optimierungspotentiale zu nutzen. Unterstützt wird er dabei durch eine Visualisierung der möglichen Unterschiede im Anfrageergebnis.

Data Stream Application Manager (DSAM)

We present our Data Stream Application Manager (DSAM). DSAM integrates different data stream management systems (DSMS) and also sensor network nodes. The user enters a query written in a system-independent declarative query language into a central control program. DSAM analyzes this query and distributes it to the available DSMSs. The distribution algorithm uses a cost model to minimize overall processing and transmission costs. The demo shows some scenarios in which DSAM can be used. We do not focus on concrete applications but on generic use-cases where DSAM may help users or application developers. One example is switching to a different DSMS without changing queries. Another example is the automatic integration of different DSMSs to make them appear just like one system.

Metadata Categories for Supporting Concurrent Engineering

Concurrent engineering is a keyword in todays enterprises. Almost every enterprise parallelizes its engineering processes to reach a higher efficiency in designing their products. Unfortunately, the time- and cost-saving potential of concurrent engineering cannot be used to its full capacity. In fact, design problems arise and lead to a lot of rework. As we have recognized, design problems always affect the underlying data. Thus, wrong data is an indication of such problems. As a consequence, the improvement of the data quality should reduce the design problems. Although the data quality-related research community has proposed various management approaches, these approaches are too generic and thus give little guidance about what to do in a given situation. The goal of our project, DQ-Step, is to develop a solution that is both general enough to cover an entire domain, namely concurrent engineering, while remaining concrete enough to give usable guidelines to enterprises to support their engineers and finally speed up their design. In our previous work, we have already identified the major problems in concurrent engineering. In this paper, we discuss the metadata categories required to help overcome these problems.

Towards an adaptive event dissemination middleware for MMVEs

The Massive Multiuser Event InfraStructure (M2etis) project is aimed at a generic middleware that supports the optimization of event dissemination based on a multidimen- sional semantic classification of event types. In this paper, we introduce the M2etis system architecture with its core concepts.