How a Distributed application differs from client server application,

[jacob deiter]

How a Distributed application differs from client server application,

I read a book; it says that, in distributed application each tier in separate computer. as per my understanding client server application each tier in separate computer

Client server application can have 3 tier like presentation tier, business logic tier(jboss) and database tier (oracle)

Distributed application also can have 3 tier like presentation tier, business logic tier and database tier.

[Adeel Ansari]

Distributed application means, an application itself distributed on several machines. Think of an appplication deployed on JBoss, since you mentioned it specifically, in clustered environment.

Further, the database can be distributed among several machines. That is known as Distributed Database.

[Adeel Ansari]

As a matter of fact, you can say a client server app is a two-tier distributed application. Database will not be counted as an application tier actually. Its a separate thing and can serve many different application, without being a part of any, particularly.

Loosely speaking, Web applications don't come in this client/server category. Because all you have is the application on the server. Client has nothing but the browser.
[ October 29, 2008: Message edited by: Adeel Ansari ]

[Paul Sturrock]

Distributed application means, an application itself distributed on several machines

A distributed application need not be distributed accross multiple physical machines. A distributed application could be one that runs on the same machine accross multiple JVMs for example.

Loosely speaking, Web applications don't come in this client/server category. Because all you have is the application on the server. Client has nothing but the browser.

This is a debatable point, given what is possible in a browser using AJAX, JavaScript, CSS, Flash, Java, ActiveX etc. It would be possible (though probably not advisable) to have a fairly dumb server application and a spectacularaly complex client application in a browser.
[ October 29, 2008: Message edited by: Paul Sturrock ]

[jacob deiter]

an application itself distributed on several machines

it means that all tiers(presentation,business ,persistence) of an application are distributed across many JVM in Many computers.for example if I want 5 kind of presentation then I can distribute across 5 physical computers ,then business logic across many physical computers

Database will not be counted as an application tier actually

then what represent database layer?

Loosely speaking, Web applications don't come in this client/server category

Can I say web application as single tier if the client is very thin client?

[Adeel Ansari]

Originally posted by Paul Sturrock:
This is a debatable point, given what is possible in a browser using AJAX, JavaScript, CSS, Flash, Java, ActiveX etc. It would be possible (though probably not advisable) to have a fairly dumb server application and a spectacularaly complex client application in a browser.

Thats the reason, I said loosely. And normally, when we mean web application, we don't say client/server application. And when we really mean client/server application, we don't say web app. That was my point.
[ October 29, 2008: Message edited by: Adeel Ansari ]

[Adeel Ansari]

Originally posted by Paul Sturrock:
A distributed application need not be distributed accross multiple physical machines. A distributed application could be one that runs on the same machine accross multiple JVMs for example.

Definitely, I forgot to make this point clear. Thanks for your clarification.
[ October 29, 2008: Message edited by: Adeel Ansari ]

[Adeel Ansari]

Originally posted by jacob deiter:
it means that all tiers(presentation,business ,persistence) of an application are distributed across many JVM in Many computers.for example if I want 5 kind of presentation then I can distribute across 5 physical computers ,then business logic across many physical computers

I think, you are mixing layer with tiers.

Originally posted by jacob deiter:
then what represent database layer?

I meant Database Server. Which is separate independent system.

Originally posted by jacob deiter:
Can I say web application as single tier if the client is very thin client?

No. It can be a n-tier application, distributed over different JVMs or/and machines.