1. A Distributed Web Information System Platform for High Responsiveness and Fault Tolerance Jordi Bataller, Hendrik Decker, Luis Irún, Francesc Muñoz Instituto Tecnológico de Informática Universidad Politécnica Valencia, Spain

2. A Distributed Web Information System Platform for High Responsiveness & Fault Tolerance High Availability & Consistency Jordi Bataller, Hendrik Decker, Luis Irún, Francesc Muñoz Instituto Tecnológico de Informática Universidad Politécnica Valencia Replicated ! Development Operation also OO, graphics dissemination Master Mind new protocols. private non-profit on campus

3. DIWISA Middleware to develop and run a distributed o-o web information system based on off-the-shelve DBMS IS Application DBMS Application DBMS D I W I S A Application DBMS DB

4. Concurrent Users, Distributed Servers, High Data Locality W I S Application No replication Partial replication Total replication DB W I S

5. Developer’s and User’s transparent view Application WIS Replicated Data DWIS DDB Distributed WIS WIS DB Distributed DBMS

6. ¿ Is Distribution + Replication worth the Effort ? Fast Access to Local Data Fault Tolerance High Availability Ease of Development Complex Distributed Concurrency Protocols Limited Network Capacities, Recovery needs to be solved High Responsiveness

7. Centralized, Object-Relational Some support for different isolation levels Industry standard integrity checking Open Source Centralized, Relational No good transaction support (patches...) Almost no integrity support (patches...) Very fast reads (updating not recommended...) Open Source Distributed Object-Relacional DBMS Industry standard support for Transactions and Integrity Commercial Distributed Relational DBMS Standard support of transactions and integrity Commercial DB2 INFORMIX INGRES

8. Results of market analysis : scant DBMS support distribution (consistency, recovery) little DBMS support for distributed object orientation Application development is difficult, costly and possibly not backward- nor upward-compatible Conclusion : DIWISA

9. LIBRARY MANAGER UDS DIWISA API for application development Provides object-oriented data access Core Component of DIWISA Communication with other DIWISA Managers Consistency Protocols Recovery Protocols communicates with only one UDS Translation of Manager’s function calls to native underlying database provides API supports distribution provides Object Orientation

10. LIBRARY MANAGER UDS D I W I S AD I W I S A LIBRARY MANAGER UDS DBMS D I W I S AD I W I S A JDBC DB

11. Summary of highlights Transform off-the-shelve DBMS into full-fledged WAN -based distributed (o-o) DB system underlying WISs Flexible Replication, optimizes tradeoff Availability/Consistency Innovative Architecture, open for different networks, interfaces, libraries, protocols Pluggable protocols for message passing, transaction processing, replication, recovery Innovative concept of fault tolerance and error recovery Fully operational prototype (Java) is up and running still needed: performance improvements, theoretical foundation