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Overview of Database Federation and IBM Garlic

Project

Presented by Xiaofen He

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Reference Data Integration through database

federation, L.M. Haas, E.T.Lin, M.A. Roth

Towards Heterogeneous Multimedia Information Systems: The Garlic Approach, IBM Almaden Research Center

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Outline Approaches to data integration Database Federation in IBM DB2 IBM Garlic Project

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Various Approaches to Data Integration (1) Application-specific solutions

Always works Expensive, fragile and hard to extend

Application-integration frameworks Protection from changes of data source Do not address data integration issues

Workflow frameworks Limited support for comparing and

manipulating

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Various Approaches to Data Integration (2) Digital libraries

Meta search engine No combination of data

Data warehousing Powerful, high-level query language May not be possible or cost effective, loss of

functionality Database federation

Virtual data warehouse Performance tradeoff (query rewrite & cost-

based optimization)

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Database Federation Basics of Database Federation DB2 styles of database federation Determining the style of database

federation to use

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Basics of Database Federation What is ‘database federation’ (DF)

Aka. ‘mediation’ An architecture in which middleware,

consisting of a relational database management system, provides uniform access to a number of heterogeneous data sources

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Common Mediation Architecture Data Source Wrapper Mediator

Figure 1. Common Mediator Architecture

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Goals of IBM DF Transparency Support heterogeneity A high degree of function Extensibility Openness Autonomy of individual data sources Query optimization

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DB2 architecture for DF

Figure 2. DB2 architecture for database Federation

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DB2 Styles of federation Scalar UDFs:

Federating function

Table UDFs: Federating data

Wrappers: Federating function and data

Figure 3. Different styles of federation

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Wrapper Architecture Multi-server integration Multi-dataset integration and

multi-operation integration Optimization Transactional integration

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Determining the style of DF to use

Figure 4. Determine the style of federation to use

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IBM Garlic Project Introduction Overview

Architecture Repositories and Databases

The Garlic Data Model Queries in Garlic Interface and Application Conclusion

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Introduction Need Goal Object-Oriented Model

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Garlic OverviewC++ Application Query/Browser

Query Services & Runtime System Metadata

Repository

Repository Wrapper

Repository Wrapper

Repository Wrapper

Repository Wrapper

Complex Object

Repository

Data Repository

Data Repository

Data Repository

Figure 5. Garlic System Architecture

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Garlic Overview Repositories

Repository type Repository instance Repository manager

Databases Global schema Wrapper schemas (local schemas)

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Garlic Data Model (1) ODMG-93 object model

Objects and values Inheritance

Object identity Weak identity – unique, not

necessarily immutable Legacy references

Implementation-constrained reference

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Garlic Data Model (2) Extensions

Degree of support for alternative implementations of interfaces

Type system flexibility - conformity Object-appropriate view definition

facility Object-Centered Views

Enhance objects by adding or hiding some of their attributes/methods.

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Queries in Garlic Query language

Object-oriented extension of SQL Integrating approximate match query

semantics with traditional exact match query semantics.

Query Processing Decomposition

Interesting Question How to characterize the query power of a

repository, in terms of the language subset that its wrapper is capable of processing directly

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Interfaces and Applications C++ API

Compiled applications Dynamic applications

Query/Browser A dynamic application Moving back and forth between

querying and browsing activities

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Summary Database Federation

A powerful tool for integrating data Future work

to improve the ease of use Enhance the performance

Garlic Project New research in many dimensions