Middleware Fatemeh Hendijanifard 1 آزمايشگاه سيستم هاي هوشمند (

Middleware Definitions “The glue which connects objects which are distributed across multiple heterogeneous computer systems” “An extension of the operating system which provides a transparent communication layer to the applications” “A software layer that serves to shield the application of the heterogeneity of the underlying computer platforms and networks”

Categories Transactional (Distributed Tuples) Message oriented (Message-Oriented Middleware) Procedural (Remote Procedure Call) Object (Distributed Object Middleware) 3 آزمايشگاه سيستم هاي هوشمند (

Transactional middleware ارایه مفهوم انتزاعی از tuple (SQL) انجام تراکنش های توزیع شده (DTP protocol) Message oriented (MOM) ارایه مفهوم انتزاعی از mailbox پیغام های آسنکرون Procedural (RPC) مفهوم انتزاعی از procedure تعامل سنکرون بین کاربر و کارگزار Object and component مفهوم انتزاعی از object تعامل ( آ ) سنکرون بین کاربر و کارگزار

Examples XML-RPC SOAP CORBA (D)COM.NET

Transactions on distributed relational database IBM CICS BEA Tuxedo LDAP (simple protocol to access remote directories, no transactions)

Message oriented middleware Java Message Queue IBM MQSeries

Remote procedure calls (RPC) Unix RPC’s DCE RPC (Distributed Computing Environment) Windows RPC’s XML-RPC

Object middleware CORBA ActiveX COM, DCOM Java RMI, Enterprise Java Beans

Middleware examples XML-RPC, SOAP RPC on top of HTTP CORBA Distributed objects COM / DCOM Microsoft’s Component Object Model.NET Microsoft’s answer to J2EE

CORBA Support for distributed object application. Allows remotely located objects to communicate with each other. Real name: (Object Management Group’s Common Object Request Broker Architecture) : OMG’s CORBA

CORBA (cont. ) Introduced in 1991 by OMG Uses C/S models where clients issue requests to objects. (any object can be C or S or both) Any interaction between objects is through requests. Supports static binding. (identify objects at compile time) An Interface Definition Language (IDL) has been defined specially for CORBA.

CORBA (cont. ) > 800 companies: Conceptual view:

CORBA (cont. ) Static interfaces Specific for each object type Dynamic interfaces Same interface independent of target object Object adapter Object references, object (de) activation, method invocation,...

Stubs and skeletons Generated from the Interface Definition (in IDL) Using appropriate language mappings Interface Definition Language Purely descriptive, not an implementation language Strongly typed

ActiveX Introduced by Microsoft at As a complete environment for components and distributed objects. Server facilities such as SQL servers and legacy access gateways can be invoked from ActiveX. Web technologies( java applets, browsers) can be intermixed with desktop tools( word processor) for distributed applications.

C/S Middleware to Access the Data Warehouse

MVS-DB2 warehouse UNIX-RDBMS warehouse PS2 RDBMS warehouse PC Client 1. DRDA for exchange protocol 2. ODBC for API 1.DRDA for DB2 on UNIX 2.Proprietary exchange protocols for other RDBMSs 3.ODBC for API 1.DRDA for DB2 on PS2 2.Proprietary exchange protocols for other RDBMSs 3.ODBC for API UNIX Client 1.DRDA for exchange protocol 2. proprietary for API 1.DRDA for DB2 on UNIX 2.Proprietary exchange protocols for other RDBMSs 3. Proprietary for API 1.DRDA for DB2 on PS2 2.Proprietary exchange protocols for other RDBMSs 3. Proprietary for API Mac Client

C/S Middleware to Access the Data Warehouse ODBC may be used widely to access data warehouse databases from different database vendors. DRDA may be used in centralized data warehouses to access DB2 data from client tools from different vendors. Proprietary exchange protocols from different C/S vendors such as EDA/SQL, Informix, Oracle and Sybase may be used.

More Details of the other two middle wares ONC RPC SOAP XML-RPC protocol ?!

XML-RPC protocol Uses XML to transmit and receive RPC’s Defines the bare minimum to get RPC’s across the network Based on HTTP with the POST method Request is an XML document containing a method name and parameters Response is an XML document with returned values

SOAP (Simple Object Access protocol) Successor of XML-RPC HTTP Header Content-Type: text/xml Content-Length must be specified and correct User agent must be specified Host must be specified Document content Root Contains name of method: Contains list of parameters: Each parameters is a pair, Data types supported String, integer, float, date, binary, boolean Array, struct

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Examples of Middleware Database access technology - e.g ODBC (Open Data Base Connectors) Java’s database connectivity API : JDBC Remote computation products - e.g ONC RPC, OSF RPC and RMI (Java Remote Method Invocation) Distributed Computing Environment (DCE) products, Common Object Request Broker Architecture (CORBA), Distributed Component Object Model (DCOM) TP - Monitors