DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson Database Middleware Early client/server database systems –Two tier –Server does business logic (data analysis & report generation) –Server does database logic –Client communicates directly with database on the server –Client does data formatting and display –Primitive middleware is simply for enabling communication

DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson Database middleware Business logic – data analysis and report generation takes place on client Data is needed at the client Server logic to selectively extract needed data from tables for transmission to client – not entire files

DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson SQL Structured Query Language ANSI standard American National Standards Institute Standard allows interoperability Provides Create & modify tables and databases Add, delete, modify and manipulate data Query Interfaces through programming languages Vendors provide enhanced features not part of ANSI SQL –Competitive advantage –Compromises transparent interoperability

DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson SQL processing 1.Application generates SQL query 2.Query goes to client middleware 3.Query is passed (through layers) across network 4.Server middleware submits query 5.Database interprets query – result is a dataset 6.Dataset is transmitted across network to client middleware 7.Data is presented to the client application Final execution of query is on the local dataset

DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson Proprietary API Most database vendors provide a proprietary API to link to their database platform (Oracle uses SQL*NET) Applications then become bound to a particular database Separate application versions needed for different databases One solution – a universal API translator into a specific API Microsoft ODBC – Open Database Connectivity Provides a set of non-database specific APIs Layer inserted between client application and middleware What about interfacing to multiple databases?

DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson ODBC Client Application Oracle SQL*NET NOS Physical NW Layers Oracle Server Oracle SQL*NET NOS Physical NW Layers ODBC

DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson 3 Tier ODBC Oracle Server Oracle SQL*NET NOS Physical NW Layers Client Application Client Middleware NOS Physical NW Layers SequelLink SQL*N ET NOS Physical NW Layers Sybase API Sybase Server Sybase mid-ware NOS Physical NW Layers Client Middle- ware

DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson Universal Data Access An alternative solution (newer) OLE DB: Object Layering and Embedded Database API Inserts another layer of middleware on the server side Clients generate OLE DB rather than a proprietary API or SQL

DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson OLE DB Client Application Client Middleware OLE NOS Physical NW Layers SQL Database ODBC NOS Physical NW Layers OLE DB Client SQL Database ODBC NOS Physical NW Layers OLE DB Client

DB MidWare CSIS 4490 N-Tier Client/Server Dr. Hoganson Web Middleware Middleware to make the application browser-compatible Development environments Examples –ActiveX –Java –CGI (Common Gateway Interface)