Middleware Technologies compiled by: Thomas M. Cosley

Introduction 4 Middleware is connectivity software that provides a mechanism for processes to interact with other processes running on multiple networked machines. 4 Middleware Application Programming Interfaces provide a more functional set of capabilities than the OS and network services provide on their own.

Middleware Architecture Platform – OS Platform – OS Middleware (Distributed Systems Services) API’s Platform Interface Application Network Interface

Types of Middleware 4 There are four basic types of middleware –Transaction Processing Monitor (TP) –Remote Procedure Call (RPC) –Message-Oriented Middleware (MOM) –Object Request Broker (ORB)

Transaction Processing (TP) 4 TP can provide the following –control transaction applications –provide business logic/rules –database updates

Transaction Processing Architecture Client TP Monitor Transaction Requests Processing Routines

Remote Procedure Call (RPC) 4 RPC is a client/server mechanism that allows the program to be distributed across multiple platforms. 4 RPC’s reduce the complexity of a system that spans multiple operating systems and network protocols by hiding OS and network interface details from the programmer.

Remote Procedure Call (cont’d) 4 RPC’s are usually implemented by: –proprietary products –proprietary development tools that create client server stubs 4 Most RPC implementations use a synchronous (call/wait) protocol to communicate between client and server.

RPC Architecture RPC STUB RPC STUB Client App Server App TRANSPORTTRANSPORT TRANSPORTTRANSPORT NETWORKNETWORK NETWORKNETWORK Application Specific procedure invocations and returns

Message Oriented Middleware (MOM) 4 Message-oriented middleware –functionality similar to RPC –provides asynchronous communication between client and server applications by queueing messages temporarily when one or the other is busy or not connected.

Server App MOM Architecture Client App TRANSPORTTRANSPORT TRANSPORTTRANSPORT NETWORKNETWORK NETWORKNETWORK Application specific proprietary messages MOM With message queue With message queue

Object Request Broker (ORB) 4 ORB’s overcome; machine, software and vendors are no boundaries for the ORB. 4 Major functionality includes: –interface definition –location and activation of remote objects –communication between clients and objects

ORB Architecture Client Remote Service (object) Request Service activate Service Establish connection communicate