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What are ORB-IOR-a servant-a POA manager

In CORBA, what are i) an ORB ii) an IOR iii) a servant iv) a POA and v) a POA manager?

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i) Object Request Broker – is a piece of middleware software which permits programmers to make program calls from one computer to other through a network. ORBs promote interoperability of the distributed object systems since they enable users to form systems by piecing altogether objects from various vendors, and hence they communicate with each other through ORB.

ii) Interoperable Object Reference - An Interoperable Object Reference (IOR) is CORBA or RMI-IIOP reference which uniquely recognized an object on a remote CORBA server. IORs can be transmitted in binary over TCP/IP general General Inter-ORB Protocol (the encoding might be big-endian or little-endian), or serialized into a string of hexadecimal digits (that is, prefixed by the string IOR to facilitate transport by non-CORBA mechanisms like HTTP, FTP, and e-mail.

iii) A Servant – a Servant is an invocation target, having methods for handling the remote process invocations. In newer CORBA versions, the remote object on the server side is divided into the Object (i.e., exposed to remote invocations) and Servant (to which the former portion delegates the method calls).This can be one Servant per remote Object, or similar servant can support numerous (possibly all) objects, related with the given Portable Object Adapter. The Servant for each and every Object can be set or found “once and forever” (that is, servant activation) or dynamically selected each time the method on that object is invoked (that is, servant location). Both servant locator and servant activator can forward calls to the other server.

iv) Portable Object Adapter – It is a standard component in CORBA model. In CORBA, on server side, the POAs form a tree-like structure, where each and every POA is accountable for one or more objects being served. The branches of this tree can be independently activated or deactivated, having different code for the servant location or activation and various request handling policies.

v) Portable Object Adapter Manager – The POA manager encapsulates the processing state of one or more POAs. By invoking the operations on a POA manager, server applications can cause requests for the related POAs to be queued or discarded. Additionally, applications can employ the POA manager to deactivate the POAs.

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