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Database Application

Development

2nd December, 2010

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Lecture Preview

Database Application Development

Service-oriented Architecture

Web-Services

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A quick look (Client-Server

Architecture) Advancement in technology over the last

decade has brought new concepts andarchitectures in database applications.

No matter how we blend it up, the basicarchitecture remains same. Entity A needs aservice and asks for it where Entity B provides

it. Its mostly about location. i.e. what should be

at server and what should be at client?

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Architecture optimization

We use the most suitable architecture to our

application. How to decide that?

Is it location? What?

It is the speed + response time with which

data can be moved from one location toanother.

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Client/Server Architecture

Definition

To handle client queries the service provider

(Server) needs some kind of a managementsystem to look after concurrency, integrity,

security and other features.

In case of databases this system is DBMS

(Database Management System).

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Client/Server Architecture

Various C/Ss can be distinguished on the basis

of distribution of Application Logic

Components across clients and servers.

These are,

Presentation Component

Processing Component

Storage Component

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Application Partitioning

Its critical to the performance of the system

that how we place each of these components.

There are two, three and n-tier architectures,in each architecture,

the storage component always resides at server

The presentation component always resides at

client

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Fat / Thin

If we place processing component on client

then it is a fat client.

If we place processing component on serverthen it is a thin client.

And, if we partition it on both server and

client then, it is a distributed client.

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Fat / Thin

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3/n-tier Architecture

Here some processing can be placed at client,but usually in a typical web environment aclient is only a thin client. (what do we use

here for presentation component?) What kind of a architecture is used in an

online banking system? and why ?

How do databases are manipulated on each

of these architecture?

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Databases in 2-tier Architecture

In this architecture, a client workstation is

responsible for managing the user interface,

including presentation logic, data processing

logic, and a business rules logic.

A database server is responsible for database

storage, access and processing.

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Implementation

Most 2-tier applications are written in

languages like VB, C# or Java.

These applications are connected to databasethrough special software called Database-

Oriented Middleware. (It is an abstraction).

The process of Middleware connecting an

application to a database consists of two

parts, (Middleware acts as a glue)

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Implementation

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Implementation

An API(application programming interface)

A database driver (to connect to a specific

database e.g. SQL Server or Oracle).

Most common APIs are ODBC(Open Database

Connectivity) and ADO.NET for the Microsoft

Platform. JDBC for Java.

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Implementation

No matter which API or language is used, the

steps are as follows:

Identify and register a database driver.

Open a connection to a database.

Execute a query against the database.

Process the results of the query.

Repeat steps 3-4 as necessary.

Close the connection to the database.

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A small example

Before going to circuit, lets get acquainted

with some important terms,

Connection

Command

SQL Data Adapter

SQL Data Set

SQL Data Table

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A small example

We are going to develop a simple client and

service provider database.

We are going to use VB.NET and SQL

Server.

There are several methods for database

connectivity, lets take a look (first we will see aglimpse of SQL and SQL server then we will

look at a .NET application).

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3-Tier Applications

In three tier there is an additional server

which can be used for different purposes, it

can be used as application server.

The most common type of application here is

a Web-based Application. Here the additional

server involved is a web-server.

It can be either on intranet, internet or both.

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Web-Applications

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Web Application Components

Database Server (Storage logic and DBMS)

Web Server (handles http client requests, e.g.

IIS or Apache) Application Server

Web browser

Simple example, a registration module

developed in ASP or PhP.

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Databases in 3-tier Applications

Static Page Request

Dynamic Page Request

Web Server (IIS)

Application Server (ASP.NET)

Database Server

Database Server

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Web Services

It is a new class of applications that improves the

communication ability of systems over the web.

A common web service protocol stack is,

UDDI (Publish, Find and use services)

WSDL (Service Descriptors )

SOAP (Service Interactions, )

XML (Data Format ) Internet (Communications)

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Web Service

Lets, take a look.