Federated information systems provide access to interrelated data that is distributed over multiple autonomous and heterogeneous data sources. The integration of these sources demands for flexible and extensible architectures that balance both, the highest possible autonomy and a reasonable degree of information sharing. In current federated information systems, the integrated data sources do only have passive functionality with regard to the federation. However, continuous improvements take the functionality of modern databases beyond former limits. The significant improvement, on which this work is based on, is the ability of modern active database systems to execute programs written in a standalone programming language as user-defined functions or stored procedures from within their database management systems.
We introduce Enhanced Active Database Systems as a new subclass of active databases that are able to interact with other components of a federation using external program calls from within triggers. We present several concepts and architectures that are specifically developed for Enhanced Active Databases to improve interoperability and consistency in federated information systems. As the basic concept we describe Active Event Notifications to provide an information system with synchronous and asynchronous update notifications in real-time. Based on this functionality, Enhanced Active Databases are able to actively participate in global integrity maintenance executing partial constraint checks on interrelated remote data. Furthermore, we present an architecture for a universal wrapper component that especially supports Active Event Notifications, which makes it perfectly suitable for event-based federated systems with real-time data processing. This tightly coupled wrapper architecture is used to build up the Dígame architecture for a peer data management system with push-based data and schema replication. Finally, we propose a Link Pattern Catalog as a guideline to model and analyze P2P-based information systems.
Contents
1 Introduction
1.1 Motivation
1.2 Overview
2 Federated Information Systems
2.1 Why not one big database?
2.2 Basic Architecture
2.3 Distribution, Autonomy, and Heterogeneity
2.3.1 Distribution
2.3.2 Autonomy
2.3.3 Heterogeneity
2.4 Integration Challenges
2.4.1 Schema and Data Integration
2.4.2 Entity Resolution
2.4.3 Global Integrity
2.4.4 Global Transaction Management
2.5 Common Integration Architectures
2.5.1 Federated Database Systems
2.5.2 Mediator-based Information Systems
2.5.3 Peer Data Management Systems
3 Enhanced Active Database Systems
3.1 Definition
3.2 Enhanced Activity
3.3 External Program Calls
3.4 Discussion
3.5 Current EADBS
4 Active Event Notification
4.1 Monitoring Concepts
4.1.1 The Event Monitor
4.1.2 Change Capture Methods
4.1.3 Data Delivery Options
4.2 Related Work
4.2.1 Research Projects
4.2.2 Commercial Change Capture Products
4.3 Active Event Notification
4.3.1 Pull-based Asynchronous Notification
4.3.2 Push-based Synchronous Notification
4.3.3 Push-based Asynchronous Notification
4.3.4 Pull-based Synchronous Notification
5 Global Integrity Maintenance
5.1 Active Component Database Systems
5.2 Partial Integrity Constraints
5.2.1 Definition of Partial Integrity Constraints
5.2.2 Partial Integrity Constraints as ECA Rules
5.2.3 System Interaction
5.3 Checking Global Integrity Constraints
5.3.1 Attribute Constraints
5.3.2 Key Constraints
5.3.3 Referential Integrity Constraints
5.3.4 Aggregated Constraints
5.4 Discussion
5.5 Global Constraints with COMICS
5.5.1 System Overview
5.5.2 Checking Constraints with COMICS
5.6 Related Work
6 Tightly coupled Wrappers
6.1 Wrapper Architecture
6.2 Event Detection Subsystem
6.3 Application Fields
6.4 Related Work
7 The DÍGAME Architecture
7.1 Introduction
7.2 Basic Functionality
7.3 DÍGAME Architecture Components
7.4 Characteristics
7.5 Implementation Details
7.6 Related Work
8 Link Patterns
8.1 Motivation
8.2 The Data Link Modeling Language (DLML)
8.2.1 Introduction
8.2.2 DLML Components
8.2.3 Example
8.3 Link Patterns
8.3.1 Elements of a Link Pattern
8.3.2 Classification
8.3.3 Usage
8.4 Link Pattern Catalog
8.5 Example
8.6 Related Work
9 Conclusion and Future Work
9.1 Summary
9.2 Future Work
Research Objective and Scope
This work aims to enhance the interoperability and consistency of federated information systems by introducing "Enhanced Active Database Systems" (EADBS). The primary objective is to enable autonomous and heterogeneous database components to actively participate in global integrity maintenance and to propagate data changes in real-time without sacrificing local autonomy.
- Architectural concepts for EADBS to interact with external components.
- Implementation of "Active Event Notifications" for immediate, push-based data delivery.
- Strategies for global integrity maintenance using partial integrity constraints.
- Development of a tightly coupled wrapper architecture for heterogeneous data sources.
- Guidelines for modeling data flows in federated systems via the Link Pattern Catalog.
Excerpt from the Book
3.1 Definition
Traditionally, database systems have been regarded as passive data providers that manage the storage of data and response to read and write requests issued by the users. More complex requirements regarding the integrity and consistency of the data had to be implemented in the applications themselves. But with the association of databases to highly complex information processing scenarios, with huge amounts of data or high performance requirements, database systems were extended by more comprehensive facilities to model structural and behavioral aspects of data to support the applications. Active database systems were introduced that assist applications by migrating reactive behavior from the application to the DBMS. They are able to observe special requirements of applications and react in a convenient way if necessary to preserve data consistency and integrity. The integration of active behavior in relational database systems is not particularly new and currently most commercial database systems support ECA rules, whereas the execution of triggers is mainly activated by operations on the structure of the database (e.g. insert or update a tuple) than by user-defined operations [86]. Unfortunately, the ability to react on events, especially from within the scope of trigger conditions and actions, has until recently been limited to the isolated databases they were defined at. Subsequent developments integrated special purpose programming languages (e.g. PL/SQL [74]) into the database management system to overcome some limitations of the query language and to provide a more complex programming solution for critical applications. But again, the scope of these extensions was strictly limited to the system borders of the database system, so an interaction with its environment was impossible. However, the support of ECA rules in form of triggers is necessary, but not sufficient for the concepts we propose here.
Summary of Chapters
Introduction: Provides the motivation for integrating autonomous databases and introduces the thesis's focus on Enhanced Active Database Systems (EADBS).
Federated Information Systems: Discusses the theoretical background, including distribution, autonomy, heterogeneity, and common integration challenges in federated systems.
Enhanced Active Database Systems: Defines EADBS and describes their capability to execute external programs to interact with their environment.
Active Event Notification: Presents a concept for immediate, real-time update notifications in federated systems using active capabilities.
Global Integrity Maintenance: Details how EADBS can actively maintain global integrity constraints through partial constraints and external interaction.
Tightly coupled Wrappers: Describes a universal wrapper architecture designed for real-time event delivery and interaction with EADBS.
The DÍGAME Architecture: Introduces the DÍGAME architecture for P2P-based information systems with push-based data replication.
Link Patterns: Proposes a catalog of Link Patterns and a modeling language (DLML) for recurring data flow problems in information grids.
Conclusion and Future Work: Summarizes the contributions and provides an outlook on potential future research directions.
Keywords
Federated Information Systems, Active Databases, Enhanced Active Database Systems, Global Integrity Maintenance, Event Notification, Real-time Data Delivery, Peer-to-Peer, Wrappers, Data Grid, Link Patterns, Data Integration, Consistency, Interoperability, Distributed Systems, Middleware
Frequently Asked Questions
What is the core focus of this thesis?
The thesis focuses on enhancing the functionality of modern active database systems to improve information sharing, consistency, and interoperability in federated and distributed information systems.
What are "Enhanced Active Database Systems" (EADBS)?
EADBS are a subclass of active databases that can execute external programs (written in standalone languages like Java) from within database triggers, allowing them to interact with software or hardware components beyond their own system borders.
What is the primary goal of the proposed Active Event Notification?
The goal is to enable truly immediate, real-time notification of external components about local data modifications, avoiding the performance overhead of traditional periodic polling or snapshot mechanisms.
How is global integrity maintained in these federated systems?
Integrity is maintained by decomposing global constraints into "partial integrity constraints" that are enforced locally by each component database, which can communicate with other sources during transaction execution to check remote constraints.
What role do the "Tightly coupled Wrappers" play?
These wrappers encapsulate heterogeneous data sources and provide a uniform interface for the federation, while specifically incorporating event detection and notification capabilities to support real-time data integration.
What are the key terms associated with this research?
Key terms include Federated Information Systems, Active Databases, Event Notification, Global Integrity Maintenance, Peer-to-Peer, and the Link Pattern Catalog for modeling data flows.
What is the purpose of the DÍGAME architecture?
DÍGAME is an architecture designed for P2P-based information grids that balances local autonomy with high data availability through a push-based replication strategy.
How does the Link Pattern Catalog assist developers?
It provides a standardized set of modeling guidelines and a vocabulary for describing, analyzing, and optimizing complex data flows within large-scale information grids.
- Quote paper
- Christopher Popfinger (Author), 2006, Enhanced active databases for federated information systems, Munich, GRIN Verlag, https://www.grin.com/document/79268
