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Architecture Overview
Client3
HTTP
Client1
Server
Client2
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Database
(can be on the server or separate)
Clients
• Clients are thin clients
• Can be many kinds of user devices –
PC’s, laptops, workstations, etc.
• Browser-based client applications (e.g.
HTML, Javascript) drive these
• Java client applications can be used
• Windows/client applications also possible
Server
Web Access
RMI
Business Layer
JDBC/ODBC
Database
Server (contd.)
Java RMI, Servlets, JSP’s etc.
Web Access
Middleware in business layer (EJB’s or .NET services)
Business Layer
Database
Database (SQL Server, Oracle, MySQL, etc.)
Server (contd.)
Web Access
Business Layer
Database
HTML Web Services
(communicates to/from the browser)
Formatting Services
(formats data to/from the business layer)
Server (contd.)
Session Management
Web Access
(managing client sessions)
(authentication, permissions)
Business Layer
Transaction Management
(queuing messages for each client)
Database
Business Logic
(scheduling, conflict mgmt etc.)
Database Access Layer
(formats calls unique to each DB manager)
Admin functions
Security
Maintainability
• Localize modifications
– Layered architecture
• Using layers as intermediaries
– Semantic coherence
– Generalized modules
– Testability enhanced by layering
Usability
• Clients use browsers
• User Interface – can be off the shelf
software
• Design Concerns
– Separate user interface from the rest of the
application
– Model View Controller
Weaknesses
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Performance can be an issue
Complexity – more layers, more classes
Availability (single server)
No special security considerations beyond
data access