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Bettina Kemme

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Universidad Politécnica de Madrid

Kansas State University

Armando Marques-Guedes

UNL - New University of Lisbon

Stefano R L Campana

University of Siena / Università di Siena

Queen Mary, University of London

Sajadin Sembiring

Universitas Sumatera Utara

Narayanan Kulathuramaiyer

Universiti Malaysia Sarawak (UNIMAS)

Anna University

Carlos Hernández Corbato

Delft University of Technology

Hans Vangheluwe

McGill University

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Papers by Bettina Kemme

Basic Protocols

Springer eBooks, 2010

Replication Architecture

Springer eBooks, 2010

Other Aspects of Replication

Springer eBooks, 2010

Lazy Replication

Springer eBooks, 2010

Self-Configuration and Elasticity

Springer eBooks, 2010

1-Copy-Snapshot Isolation

Springer eBooks, 2010

Eager Replication and 1-Copy-Serializability

Springer eBooks, 2010

Persistence in massively multiplayer online games

The most important asset of a Massively Multiplayer Online Game is its world state, as it represe... more The most important asset of a Massively Multiplayer Online Game is its world state, as it represents the combined efforts and progress of all its participants. Thus, it is extremely important that this state is not lost in case of server failures. Survival of the world state is typically achieved by making it persistent, e.g., by storing it in a relational database. The main challenge of this approach is to track the large volume of modifications applied to the world in real time. This paper compares a variety of strategies to persist changes of the game world. While critical events must be written synchronously to the persistent storage, a set of approximation strategies are discussed and compared that are suitable for events with low consistency requirements, such as player movements. An analysis to better understand the possible limitations and bottlenecks of these strategies is presented using experimental data from an MMOG research framework. Our analysis shows that a distance-based solution offers the scalability and efficiency required for large-scale games as well as offering error bounds and eliminating unnecessary updates associated with localized movement.

The Scalability of Replication

Springer eBooks, 2010

1-Copy-Equivalence and Consistency

Springer eBooks, 2010

Parallel and Distributed Databases

Springer eBooks, Oct 29, 2006

Motivations for parallel and distributed databases, data partitioning, client-server architecture... more

Database Replication

Springer eBooks, 2010

In this demonstration, we present ConsAD, a tool that detects consistency anomalies for arbitrary... more In this demonstration, we present ConsAD, a tool that detects consistency anomalies for arbitrary multi-tier applications that use lower levels of isolation than serializability. As the application is running, ConsAD detects and quantifies anomalies indicating exactly the transactions and data items involved. Furthermore, it classifies the detected anomalies into patterns showing the business methods involved as well as their occurrence frequency. ConsAD can guide designers to either choose an isolation level for which their application shows few anomalies or change their transaction design to avoid the anomalies. Its graphical interface shows detailed information about detected anomalies as they occur and analyzes their patterns as well as their distribution.

CumuloNimbo: A Cloud Scalable Multi-tier SQL Database

IEEE Data Eng. Bull., 2015

This article presents an overview of the CumuloNimbo platform. CumuloNimbo is a framework for mul... more This article presents an overview of the CumuloNimbo platform. CumuloNimbo is a framework for multi-tier applications that provides scalable and fault-tolerant processing of OLTP workloads. The main novelty of CumuloNimbo is that it provides a standard SQL interface and full transactional support without resorting to sharding and no need to know the workload in advance. Scalability is achieved by distributing request execution and transaction control across many compute nodes while data is persisted in a distributed data store. In this paper we present an overview of the platform.

Database replication for clusters of workstations

I would also like to thank all my colleagues from the Information and Communication Systems Group... more I would also like to thank all my colleagues from the Information and Communication Systems Group and from the Database Research Group for their friendliness, discussions, and help. Special thanks go to Guy Pardon for sharing an office with me for so many years-1 think we have built quite a good team. I am also thankful to Antoinette Förster for keeping the business running. Thanks also to all my friends for their motivating encouragement, for the stimulating discussions about research, career, and many other topics, and for being there when I needed them. A thousand thanks to Mike for his love and support. With him at my side, work seemed less hard and private time a treasure. He supported my research tremendously, kept me motivated, and was patient when I was stressed and in a bad mood. Finally, I dedicate this thesis to my family. They supported me in every respect, and were always willing to give me moral support.

Real-time quantification and classification of consistency anomalies in multi-tier architectures

2011 IEEE 27th International Conference on Data Engineering, 2011

Page 1. Real-Time Quantification and Classification of Consistency Anomalies in Multi-tier Archit... more

One-Copy-Serializability

Encyclopedia of Database Systems, 2009

Organization for the advancement of structured information standards Definition OASIS is a non-fo... more Organization for the advancement of structured information standards Definition OASIS is a non-for-profit consortium aiming at collaborative development and approval of open international, mainly XML-based, standards. Key Points OASIS was founded in 1993 under the name ''SGML Open.'' The initial goal of the organization was to develop guidelines for interoperability among products using Standard Generalized Markup Language (SGML). In 1998 it changed name to OASIS to reflect on changing scope of its technical work. OASIS consists of an open group of member organizations whose representatives work in committees developing standards, promoting standards adoption, product interoperability and standards conformance. In 2007 OASIS had 5,000 participants representing 600 organizations and individual members in 100 countries. OASIS is governed by a member-elected Board in an annual election process. The board membership is based on the personal merits of Board nominees. OASIS process allows participants to influence standards that affect their business, contribute to standards advancement and start new standards. The process is designed to promote industry consensus. OASIS strategy values creativity and consensus over conformity and control. It relies on the market to determine the particular approach taken in the development of sometimes overlapping standards. OASIS maintains collaborative relationships with the International Electrotechnical Commission

How consistent is your cloud application?

Proceedings of the Third ACM Symposium on Cloud Computing, 2012

Current cloud datastores usually trade consistency for performance and availability. However, it ... more Current cloud datastores usually trade consistency for performance and availability. However, it is often not clear how an application is affected when it runs under a low level of consistency. In fact, current application designers have basically no tools that would help them to get a feeling of which and how many inconsistencies actually occur for their particular application. In this paper, we propose a generalized approach for detecting consistency anomalies for arbitrary cloud applications accessing various types of cloud datastores in transactional or non-transactional contexts. We do not require any knowledge on the business logic of the studied application nor on its selected consistency guarantees. We experimentally verify the effectiveness of our approach by using the Google App Engine and Cassandra datastores.

Consistency anomalies in multi-tier architectures: automatic detection and prevention

The VLDB Journal, 2013

Modern transaction systems, consisting of an application server tier and a database tier, offer s... more Modern transaction systems, consisting of an application server tier and a database tier, offer several levels of isolation providing a trade-off between performance and consistency. While it is fairly well known how to identify qualitatively the anomalies that are possible under a certain isolation level, it is much more difficult to detect and quantify such anomalies during run-time of a given application. In this paper, we present a new approach to detect and quantify consistency anomalies for arbitrary multi-tier application running under any isolation levels ensuring at least read committed. In fact, the application can run even under a mixture of isolation levels. Our detection approach can be online or off-line and for each detected anomaly, we identify exactly the transactions and data items involved. Furthermore, we classify the detected anomalies into patterns showing the business methods involved as well as analyzing the types of cycles that occur. Our approach can help designers to either choose an isolation level where the anomalies do not occur or to change the transaction design to avoid the anomalies. Furthermore, we provide an option in which the occurrence of anomalies can be automatically reduced during run-time. To test the effectiveness and efficiency of our approach, we have conducted a set of experiments using a wide range of benchmarks.

A Middleware for Consistent Data Replication: Is it feasible in WANs?

Recent proposals have shown that middleware based database replication is able to provide 1-copy-... more Recent proposals have shown that middleware based database replication is able to provide 1-copy-serializability in LAN environments with excellent performance. This can be achieved by using powerful and fast multicast primitives that deliver messages to all sites in the same order in an all-or-nothing fashion. The question is whether a similar approach is feasible in WAN environments considering the increased message latency. Some of the approaches used in LANs might also work in WANs but others will be prohibitive. We have performed extensive tests of different protocols in a WAN testbed, in order to identify the most crucial bottlenecks, and the most promising optimizations. The performance results show that performance remains acceptable even for medium sized systems consisting of up to eight sites. As such, we believe that data replication guaranteeing 1-copy-serializability is a serious alternative to weaker approaches even in WAN environments.

Basic Protocols

Springer eBooks, 2010

Replication Architecture

Springer eBooks, 2010

Other Aspects of Replication

Springer eBooks, 2010

Lazy Replication

Springer eBooks, 2010

Self-Configuration and Elasticity

Springer eBooks, 2010

1-Copy-Snapshot Isolation

Springer eBooks, 2010

Eager Replication and 1-Copy-Serializability

Springer eBooks, 2010

Persistence in massively multiplayer online games

The most important asset of a Massively Multiplayer Online Game is its world state, as it represe... more The most important asset of a Massively Multiplayer Online Game is its world state, as it represents the combined efforts and progress of all its participants. Thus, it is extremely important that this state is not lost in case of server failures. Survival of the world state is typically achieved by making it persistent, e.g., by storing it in a relational database. The main challenge of this approach is to track the large volume of modifications applied to the world in real time. This paper compares a variety of strategies to persist changes of the game world. While critical events must be written synchronously to the persistent storage, a set of approximation strategies are discussed and compared that are suitable for events with low consistency requirements, such as player movements. An analysis to better understand the possible limitations and bottlenecks of these strategies is presented using experimental data from an MMOG research framework. Our analysis shows that a distance-based solution offers the scalability and efficiency required for large-scale games as well as offering error bounds and eliminating unnecessary updates associated with localized movement.

The Scalability of Replication

Springer eBooks, 2010

1-Copy-Equivalence and Consistency

Springer eBooks, 2010

Parallel and Distributed Databases

Springer eBooks, Oct 29, 2006

Motivations for parallel and distributed databases, data partitioning, client-server architecture... more

Database Replication

Springer eBooks, 2010

In this demonstration, we present ConsAD, a tool that detects consistency anomalies for arbitrary... more In this demonstration, we present ConsAD, a tool that detects consistency anomalies for arbitrary multi-tier applications that use lower levels of isolation than serializability. As the application is running, ConsAD detects and quantifies anomalies indicating exactly the transactions and data items involved. Furthermore, it classifies the detected anomalies into patterns showing the business methods involved as well as their occurrence frequency. ConsAD can guide designers to either choose an isolation level for which their application shows few anomalies or change their transaction design to avoid the anomalies. Its graphical interface shows detailed information about detected anomalies as they occur and analyzes their patterns as well as their distribution.

CumuloNimbo: A Cloud Scalable Multi-tier SQL Database

IEEE Data Eng. Bull., 2015

This article presents an overview of the CumuloNimbo platform. CumuloNimbo is a framework for mul... more This article presents an overview of the CumuloNimbo platform. CumuloNimbo is a framework for multi-tier applications that provides scalable and fault-tolerant processing of OLTP workloads. The main novelty of CumuloNimbo is that it provides a standard SQL interface and full transactional support without resorting to sharding and no need to know the workload in advance. Scalability is achieved by distributing request execution and transaction control across many compute nodes while data is persisted in a distributed data store. In this paper we present an overview of the platform.

Database replication for clusters of workstations

I would also like to thank all my colleagues from the Information and Communication Systems Group... more I would also like to thank all my colleagues from the Information and Communication Systems Group and from the Database Research Group for their friendliness, discussions, and help. Special thanks go to Guy Pardon for sharing an office with me for so many years-1 think we have built quite a good team. I am also thankful to Antoinette Förster for keeping the business running. Thanks also to all my friends for their motivating encouragement, for the stimulating discussions about research, career, and many other topics, and for being there when I needed them. A thousand thanks to Mike for his love and support. With him at my side, work seemed less hard and private time a treasure. He supported my research tremendously, kept me motivated, and was patient when I was stressed and in a bad mood. Finally, I dedicate this thesis to my family. They supported me in every respect, and were always willing to give me moral support.

Real-time quantification and classification of consistency anomalies in multi-tier architectures

2011 IEEE 27th International Conference on Data Engineering, 2011

Page 1. Real-Time Quantification and Classification of Consistency Anomalies in Multi-tier Archit... more

One-Copy-Serializability

Encyclopedia of Database Systems, 2009

Organization for the advancement of structured information standards Definition OASIS is a non-fo... more Organization for the advancement of structured information standards Definition OASIS is a non-for-profit consortium aiming at collaborative development and approval of open international, mainly XML-based, standards. Key Points OASIS was founded in 1993 under the name ''SGML Open.'' The initial goal of the organization was to develop guidelines for interoperability among products using Standard Generalized Markup Language (SGML). In 1998 it changed name to OASIS to reflect on changing scope of its technical work. OASIS consists of an open group of member organizations whose representatives work in committees developing standards, promoting standards adoption, product interoperability and standards conformance. In 2007 OASIS had 5,000 participants representing 600 organizations and individual members in 100 countries. OASIS is governed by a member-elected Board in an annual election process. The board membership is based on the personal merits of Board nominees. OASIS process allows participants to influence standards that affect their business, contribute to standards advancement and start new standards. The process is designed to promote industry consensus. OASIS strategy values creativity and consensus over conformity and control. It relies on the market to determine the particular approach taken in the development of sometimes overlapping standards. OASIS maintains collaborative relationships with the International Electrotechnical Commission

How consistent is your cloud application?

Proceedings of the Third ACM Symposium on Cloud Computing, 2012

Current cloud datastores usually trade consistency for performance and availability. However, it ... more Current cloud datastores usually trade consistency for performance and availability. However, it is often not clear how an application is affected when it runs under a low level of consistency. In fact, current application designers have basically no tools that would help them to get a feeling of which and how many inconsistencies actually occur for their particular application. In this paper, we propose a generalized approach for detecting consistency anomalies for arbitrary cloud applications accessing various types of cloud datastores in transactional or non-transactional contexts. We do not require any knowledge on the business logic of the studied application nor on its selected consistency guarantees. We experimentally verify the effectiveness of our approach by using the Google App Engine and Cassandra datastores.

Consistency anomalies in multi-tier architectures: automatic detection and prevention

The VLDB Journal, 2013

Modern transaction systems, consisting of an application server tier and a database tier, offer s... more Modern transaction systems, consisting of an application server tier and a database tier, offer several levels of isolation providing a trade-off between performance and consistency. While it is fairly well known how to identify qualitatively the anomalies that are possible under a certain isolation level, it is much more difficult to detect and quantify such anomalies during run-time of a given application. In this paper, we present a new approach to detect and quantify consistency anomalies for arbitrary multi-tier application running under any isolation levels ensuring at least read committed. In fact, the application can run even under a mixture of isolation levels. Our detection approach can be online or off-line and for each detected anomaly, we identify exactly the transactions and data items involved. Furthermore, we classify the detected anomalies into patterns showing the business methods involved as well as analyzing the types of cycles that occur. Our approach can help designers to either choose an isolation level where the anomalies do not occur or to change the transaction design to avoid the anomalies. Furthermore, we provide an option in which the occurrence of anomalies can be automatically reduced during run-time. To test the effectiveness and efficiency of our approach, we have conducted a set of experiments using a wide range of benchmarks.

A Middleware for Consistent Data Replication: Is it feasible in WANs?

Recent proposals have shown that middleware based database replication is able to provide 1-copy-... more Recent proposals have shown that middleware based database replication is able to provide 1-copy-serializability in LAN environments with excellent performance. This can be achieved by using powerful and fast multicast primitives that deliver messages to all sites in the same order in an all-or-nothing fashion. The question is whether a similar approach is feasible in WAN environments considering the increased message latency. Some of the approaches used in LANs might also work in WANs but others will be prohibitive. We have performed extensive tests of different protocols in a WAN testbed, in order to identify the most crucial bottlenecks, and the most promising optimizations. The performance results show that performance remains acceptable even for medium sized systems consisting of up to eight sites. As such, we believe that data replication guaranteeing 1-copy-serializability is a serious alternative to weaker approaches even in WAN environments.