ISYS 546Client/Server Database

Application Development

Database Application• Database application is a program that

interacts with the database at some point in its execution.

• It consists of an organized set of menus, forms, reports, business rules, and the database it operates on.

Evolution of Multi-User Database Application Architectures

• Teleprocessing: – One computer with a single CPU and a number of dumb terminals.– Add burden on the central computer, which not only had to run the

application programs and DBMS, but also had to carry out a significant amount of work on behalf of the terminals (such as formatting data for display)

• File-Server: – Applications run on workstations that contain a full copy of the

DBMS. File-server acts as a shared hard disk drive. The DBMS on each workstation sends requests to the file-server for data, but none of the processing is done by the server.

– Generate a significant amount of network traffic.

• Client-Server: – Computer network development– Balanced distributed processing

Client Database Server

SQL queries

Results

Database Server: A high processing power computer with advanced DBMS.

Client: A PC that runs database applications.

SQL interface.

Client Functions

• Manages the user interface.

• Accepts and checks syntax of user input.

• Implements business rules.

• Generates database requests and transmits to server.

• Passes response back to user.

Database Server Functions

• Checks authorization.• Accepts and processes database requests from

clients.• Ensures integrity constraints not violated.• Performs query/update processing and transmits

response to client.• Provides concurrent database access, transaction

management, and recovery control.

Advantages of Client-Server Architecture

• Enables wider access to databases.• Increased performance: Different CPUs can be

processing applications in parallel.• Hardware costs may be reduced: Only server

requires higher storage and processing power to manage the database.

• Network traffic is reduced: Only database requests and results are sent.

• Increased database integrity.

The three components in a database application

1. Presentation – user interface• Menus, forms, reports, etc

2. Processing logic • Business rules

3. Database

Categories of Database Applications

• One-Tier– Legacy online transaction processing– PC database application

• Two-Tier client/server– Client-based presentation.– Processing logic is buried either inside the user interface

on the client or within the database on the server, or both.

• Three-Tier, N- tier– Processing logic is separated from the interface and

database.

Two-tier

• Simplicity• Provides a basic separation of tasks. The client is

primarily responsible for the presentation of data to user, and the server is primarily responsible for supplying data services to the client.

• Fat client: – More functions are placed on the client

• Fat server: – More functions are placed on the server.

Three-Tier

• 1. User interface, 2. Business logic and data processing layer, 3. Database server.

• Advantage:– Implementing business rules as components.

• Objects that provide services to other client applications.

– Application maintenance is centralized.

– Separation of the business logic from the database functions.

– Fit naturally to the Internet environment.

Benefits of Building Applications from Components

• Reusability– Many applications can share the services provided

by the same component.

• Manageability– By dividing a program into components, a project

can be divided into smaller, more manageable tasks, and each individual programmers can build components for which their skills are best suited.

• Maintenance– Each component can be maintained as an

individual unit.

Progression of the Internet• Hypertext web

– Publishing static web pages

• Simple response web – Dynamic database pages– Stateless

– Cookies

– Maintain session with server side scripts, ASP, JSP

• Object web– Provides object- to –object interactions between client

object and server object.

– Require web server to mediate between objects running on the client and objects running on the server.

The Web as a Database Application Platform

• Three-tier architecture– Browser, web server, database server,

processing logic

• Advantages:– Cross-platform support– Graphical user interface

The Web as a Database Application Platform

• Disadvantages– Reliability: Internet is unreliable and slow.– Security– Costs: hardware and software 20%, marketing

24%, content development 56%.– Potentially enormous peak load.

Approaches to Integrating the Web and DBMSs

• Common Gateway Interface (CGI)– Lack of transaction support due to the

statelessness of HTTP. The database server must perform the same logon and logout for every query submitted by the same user.

• JAVA 2 Platform• Microsoft Platform• Others

Java 2 Platform

• Presentation Tier:– JavaScript, Java applet

• Server site scripting:– Java Server Pages

• Business tier:– Enterprise Java Beans (EJB): A standard for building

server-site components in Java.

• Database access:– JDBC– SQLJ: Static embeded SQL in Java.

Old Microsoft Platform

• Presentation Tier:– VBScript, JScript

• Web server and Server site scripting:– Internet Information Server, Active Server Pages

• Business tier:– COM ActiveX components

• Component Object Model consists of a specification that defines the interface between objects and an implementation packaged as a Dynamic Link Library (DLL).

• Database access:– ODBC: An interface to access relational databases.

.Net Architecture

Common Language Runtime

Base Class Library

Data and XML

ASP.Net Windows Forms

Common Language Specification

VB.Net C# C++

Microsoft’s .Net

• Language must compliance with Common Language Specification, CLS.

• Compile the language into Microsoft Intermediate Language (MSIL) code.

• The MSIL code is then executed in the Common Language Runtime (CLR), which conceptually is same as the JVM, where it is translated into machine code by a compiler.

• Common Language Runtime:– Manages execution of compiled .NET program.– Provides .Net basic services, such as memory

management, garbage collection, etc.

• Base Class library: define all the basic data types such as system.object, numeric, date, etc.

• Data and XML: Classes work with database (ADO.NET) and XML document.

• ASP.Net and Forms: Classes that generate user interface.

• CLS: CLS dictates the minimum group of features that a .Net language must have.

.Net Advantages

• It is independence from a specific language. Developers can create a .Net application in any .Net compatible language.– .Net moves most of the functionality from the language

to the .Net Framework. All .Net languages can use these classes.

• It can exist on multiple platforms, further extending the portability of .Net programs.

• Facilitate internet application development:– ASP.Net: Web Forms and XML Web services.

• Universal data access: Data can be accessed by any Internet-connected device.

Programming in the .Net Framework

• Programming in the .Net Framework means making use of the classes, objects, and members exposed by the Framework, building your own classes on top of these and manipulating the resulting objects using a .Net language.

Techniques Covered in ISYS546

• Prerequisites: Programming, Database, SQL• .Net Framework• Visual Basic .NET

– Interface and event-driven programming– Class and component programming

• Database programming– ADO.NET programming model

• Web Techniques:– Server side scripting: ASP.NET– Web services:

• Introduction to XML