distributed computing A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another from any system. Distributed computing is a field of computer sc ...

, an object request broker (ORB) is a

middleware Middleware is a type of computer software that provides services to software applications beyond those available from the operating system. It can be described as "software glue". Middleware makes it easier for software developers to implement com ...

which allows program calls to be made from one computer to another via a computer network, providing location transparency through

remote procedure call In distributed computing, a remote procedure call (RPC) is when a computer program causes a procedure ( subroutine) to execute in a different address space (commonly on another computer on a shared network), which is coded as if it were a normal (l ...

s. ORBs promote interoperability of distributed object systems, enabling such systems to be built by piecing together objects from different vendors, while different parts communicate with each other via the ORB.

Overview

ORBs handle the transformation of in-process data structures to and from the raw byte sequence, which is transmitted over the network. This is called marshalling or

serialization In computing, serialization (or serialisation) is the process of translating a data structure or object state into a format that can be stored (e.g. files in secondary storage devices, data buffers in primary storage devices) or transmitted (e ...

. In addition to marshalling data, ORBs often expose many more features, such as

distributed transactions A distributed transaction is a database transaction in which two or more network hosts are involved. Usually, hosts provide transactional resources, while the transaction manager is responsible for creating and managing a global transaction that enc ...

, directory services or real-time scheduling. Some ORBs, such as

CORBA The Common Object Request Broker Architecture (CORBA) is a standard defined by the Object Management Group (OMG) designed to facilitate the communication of systems that are deployed on diverse platforms. CORBA enables collaboration between sys ...

-compliant systems, use an

interface description language interface description language or interface definition language (IDL), is a generic term for a language that lets a program or object written in one language communicate with another program written in an unknown language. IDLs describe an inter ...

to describe the data that is to be transmitted on remote calls. In

object-oriented language Object-oriented programming (OOP) is a programming paradigm based on the concept of " objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pr ...

s, an ORB actually provides a framework which enables remote objects to be used over the network, in the same way as if they were local and part of the same

process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management * Business process, activities that produce a specific s ...

. On the client side, so-called ''stub'' objects are created and invoked, serving as the only part visible and used inside the client application. After the stub's methods are invoked, client-side ORB performs the marshalling of invocation data, and forwards the request to the server-side ORB. On the server side, ORB locates the targeted object, executes the requested operation, and returns the results. Having the results available, client's ORB performs the demarshalling and passes the results back into the invoked stub, making them available to the client application. The whole process is transparent, resulting in remote objects appearing as if they were local.

Implementations

- Common Object Request Broker Architecture. *

ICE Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...

- the

Internet Communications Engine The Internet Communications Engine, or Ice, is an open-source RPC framework developed by ZeroC. It provides SDKs for C++, C#, Java, JavaScript, MATLAB, Objective-C, PHP, Python, Ruby and Swift, and can run on various operating systems, inclu ...

* .NET Remoting - object remoting library within Microsoft's

.NET Framework The .NET Framework (pronounced as "''dot net"'') is a proprietary software framework developed by Microsoft that runs primarily on Microsoft Windows. It was the predominant implementation of the Common Language Infrastructure (CLI) until bein ...

Windows Communication Foundation The Windows Communication Foundation (WCF), previously known as Indigo, is a free and open-source runtime and a set of APIs in the .NET Framework for building connected, service-oriented applications. .NET Core 1.0, released 2016, did not supp ...

(WCF) *

ORBexpress {{Infobox software , name = ORBexpress , logo = wl_ois_orbexpress.jpg , developer = Objective Interface Systems , released = {{Start date and age, 1998, 08 , latest release date ...

- Real-time and Enterprise ORBs by Objective Interface Systems * Orbix - An Enterprise-level CORBA ORB from

IONA Technologies IONA Technologies was an Irish software company founded in 1991. It began as a campus company linked to Trinity College Dublin had its headquarters in Dublin, and eventually also expanded its offices in Boston and Tokyo. It specialised in dist ...

* DCOM - the Distributed Component Object Model from

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washingt ...

* RMI - the Remote Method Invocation Protocol from

Sun Microsystems Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, th ...

ORBit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a ...

- an open-source CORBA ORB used as middleware for

GNOME A gnome is a mythological creature and diminutive spirit in Renaissance magic and alchemy, first introduced by Paracelsus in the 16th century and later adopted by more recent authors including those of modern fantasy literature. Its character ...

The ACE ORB The ACE ORB (TAO) is a freely available, open-source, and standards-compliant real-time C++ implementation of CORBA based upon the Adaptive Communication Environment (ACE). Availability TAO can be downloaded from the Internet and freely used ...

- a CORBA implementation from th
Distributed Object Computing (DOC) Group
* omniORB - Free CORBA OR

References

Middleware {{network-software-stub

Overview

Implementations

See also

References