Wrapperbased evolution of legacy information systems

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Wrapper-based evolution of legacy information
systems

• Philippe Thiran
• Jean-Luc Hainaut
• Djamal Benslimane

By- Kiran Yayavaram
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Introduction

• Legacy data-Intensive Applications
• Data management Systems
• Wrappers
• Data Integrity
• Data Consistency

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Wrapper Based Strategies for Information Systems
Evolution Migration

• Role of Wrappers in Systems Evolution Migration
• Translate Data Queries from the legacy data
  model and interface to those expected by the new
  component.
• Take Charge of Validation logic that ensures data
  integrity.
• Database is migrated first. New Components are
  developed on this new database, while the legacy
  components are interfaced through wrappers

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Types of Wrappers

• Forward Wrappers
• Validation logic that ensures data Integrity.
  These emulate the new technology based on the
  legacy one.
• Backward Wrappers
• Model Conversion is the only responsibility.
  These emulate the legacy technology on top of the
  new one

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Approaches for wrapper Implementation

• Wrapper Transparency
• Update Facilities

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Wrappers.

• Building Wrappers
• Wrapper Schema Definition
• Mapping Definition

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Wrapper Architecture

• Wrapper Architecture

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Wrapper Architecture

• Wrapper Query/Update Analysis
• Error Reporting
• Query/Update and Data Translation

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Abstract specification of a Wrapper

• Model and Schema Specification
• Transformational Mapping Specification
• Implicit Constraints and Schema Interpretation

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Wrapper Development

• Generic Methodology
• Database Reverse Engineering for Schema
  Definition DBRE
• Wrapper Generation
• Tool Support

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Metrics of wrapper development cost

• Factors
• Underlying DBMS to which the wrapper is dedicated
• Size of the database and wrapper schemas
• Number and the type of schema transformation of
  the sequence

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Conclusion

• Wrappers..
• Proves to be the core technology that allows a
  smooth transition to modern architectures.
• Easier integration of a legacy database into
  current large applications
• They relieve modern client components from the
  responsibility of controlling data integrity
• Error Recovery Transaction management

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• ??????...Questions...??????