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'{{more footnotes|date=February 2009}} {{Use dmy dates|date=December 2019}} {{Infobox standardref | title = Common Object Request Broker Architecture | status = Published | year_started = {{Start date and age|1991}} | version = 3.3 | versionDate = {{Start date and age|2012|10}} | preview = | previewDate = | organization = [[Object Management Group]] | base_standards = | related_standards = | abbreviation = CORBA | ___domain = | license = | website = {{URL|corba.org/}} }} The '''Common Object Request Broker Architecture''' ('''CORBA''') is a [[Standardization|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 systems on different operating systems, [[programming language]]s, and computing hardware. CORBA uses an object-oriented model although the systems that use the CORBA do not have to be object-oriented. CORBA is an example of the [[distributed object]] paradigm. == Features == The following describes some of the most significant ways that CORBA can be used to facilitate communication among distributed objects. === Objects By Reference === This reference is either acquired through a stringified [[Uniform Resource Locator]] (URL), NameService lookup (similar to [[Domain Name System]] (DNS)), or passed-in as a method parameter during a call. Object references are lightweight objects matching the interface of the real object (remote or local). Method calls on the reference result in subsequent calls to the ORB and blocking on the thread while waiting for a reply, success or failure. The parameters, return data (if any), and exception data are marshaled internally by the ORB according to the local language and OS mapping. === Data By Value === The CORBA Interface Definition Language provides the language- and OS-neutral inter-object communication definition. CORBA Objects are passed by reference, while data (integers, doubles, structs, enums, etc.) are passed by value. The combination of Objects-by-reference and data-by-value provides the means to enforce great data typing while compiling clients and servers, yet preserve the flexibility inherent in the CORBA problem-space. ===Objects By Value (OBV)=== Apart from remote objects, the CORBA and [[RMI-IIOP]] define the concept of the OBV and Valuetypes. The code inside the methods of Valuetype objects is executed locally by default. If the OBV has been received from the remote side, the needed code must be either ''[[A priori and a posteriori|a priori]]'' known for both sides or dynamically downloaded from the sender. To make this possible, the record, defining OBV, contains the Code Base that is a space-separated list of [[Uniform Resource Locator|URL]]s whence this code should be downloaded. The OBV can also have the remote methods. ===CORBA Component Model (CCM)=== CORBA Component Model (CCM) is an addition to the family of CORBA definitions.<ref>{{cite web | url=http://www.drdobbs.com/the-corba-component-model/184403888 | title=The CORBA Component Model | publisher=[[Dr. Dobb's Journal]] | date=1 September 2004 | access-date=13 March 2017}}</ref> It was introduced with CORBA 3 and it describes a standard application framework for CORBA components. Though not dependent on "language dependent [[Enterprise Java Beans]] (EJB)", it is a more general form of EJB, providing four component types instead of the two that EJB defines. It provides an abstraction of entities that can provide and accept services through well-defined named interfaces called ''ports''. The CCM has a component container, where software components can be deployed. The container offers a set of services that the components can use. These services include (but are not limited to) [[Notification system|notification]], [[authentication]], [[persistence (computer science)|persistence]] and [[transaction processing]]. These are the most-used services any distributed system requires, and, by moving the implementation of these services from the software components to the component container, the complexity of the components is dramatically reduced. === Portable interceptors === Portable interceptors are the "hooks", used by CORBA and [[RMI-IIOP]] to mediate the most important functions of the CORBA system. The CORBA standard defines the following types of interceptors: # [[Interoperable Object Reference|IOR]] interceptors mediate the creation of the new references to the remote objects, presented by the current server. # Client interceptors usually mediate the remote method calls on the client (caller) side. If the object [[Servant (CORBA)|Servant]] exists on the same server where the method is invoked, they also mediate the local calls. # Server interceptors mediate the handling of the remote method calls on the server (handler) side. The interceptors can attach the specific information to the messages being sent and IORs being created. This information can be later read by the corresponding interceptor on the remote side. Interceptors can also throw forwarding exceptions, redirecting request to another target. ===General InterORB Protocol (GIOP)=== {{Main|General Inter-ORB Protocol}} The [[General Inter-ORB Protocol|GIOP]] is an abstract protocol by which [[Object request broker]]s (ORBs) communicate. Standards associated with the protocol are maintained by the [[Object Management Group]] (OMG). The GIOP architecture provides several concrete protocols, including: # Internet InterORB Protocol (IIOP) &ndash; The Internet Inter-Orb Protocol is an implementation of the GIOP for use over the [[Internet]], and provides a mapping between GIOP messages and the [[Internet protocol suite|TCP/IP]] layer. # SSL InterORB Protocol (SSLIOP) &ndash; SSLIOP is IIOP over [[Secure Sockets Layer|SSL]], providing [[encryption]] and [[authentication]]. # HyperText InterORB Protocol (HTIOP) &ndash; HTIOP is IIOP over [[HTTP]], providing transparent proxy bypassing. # Zipped IOP (ZIOP) &ndash; A zipped version of GIOP that reduces the bandwidth usage. ===VMCID (Vendor Minor Codeset ID)=== Each standard CORBA exception includes a minor code to designate the subcategory of the exception. Minor exception codes are of type unsigned long and consist of a 20-bit "Vendor Minor Codeset ID" (VMCID), which occupies the high order 20 bits, and the minor code proper which occupies the low order 12 bits. Minor codes for the standard exceptions are prefaced by the VMCID assigned to OMG, defined as the unsigned long constant CORBA::OMGVMCID, which has the VMCID allocated to OMG occupying the high order 20 bits. The minor exception codes associated with the standard exceptions that are found in Table 3–13 on page 3-58 are or-ed with OMGVMCID to get the minor code value that is returned in the ex_body structure (see Section 3.17.1, "Standard Exception Definitions", on page 3-52 and Section 3.17.2, "Standard Minor Exception Codes", on page 3-58). Within a vendor assigned space, the assignment of values to minor codes is left to the vendor. Vendors may request allocation of VMCIDs by sending email to tagrequest@omg.org. A list of currently assigned VMCIDs can be found on the OMG website at: http://www.omg.org/cgi-bin/doc?vendor-tags The VMCID 0 and 0xfffff are reserved for experimental use. The VMCID OMGVMCID (Section 3.17.1, "Standard Exception Definitions", on page 3-52) and 1 through 0xf are reserved for OMG use. [http://www.omg.org/cgi-bin/doc?formal/98-12-01 The Common Object Request Broker: Architecture and Specification (CORBA 2.3)] ===Corba Location (CorbaLoc)=== Corba Location (CorbaLoc) refers to a stringified object reference for a CORBA object that looks similar to a URL. All CORBA products must support two OMG-defined URLs: "{{mono|corbaloc:}}" and "{{mono|corbaname:}}". The purpose of these is to provide a human readable and editable way to specify a ___location where an IOR can be obtained. An example of corbaloc is shown below: : {{mono|corbaloc::160.45.110.41:38693/StandardNS/NameServer-POA/_root}} A CORBA product may optionally support the "{{mono|http:}}", "{{mono|ftp:}}" and "{{mono|file:}}" formats. The semantics of these is that they provide details of how to download a stringified IOR (or, recursively, download another URL that will eventually provide a stringified IOR). Some ORBs do deliver additional formats which are proprietary for that ORB. == Problems and criticism == While CORBA delivered much in the way code was written and software constructed, it has been the subject of criticism.<ref name="CORBA_trouble">{{cite web |url=http://www.davidchappell.com/articles/article_Trouble_CORBA.html |archive-url=https://web.archive.org/web/20121203074323/http://www.davidchappell.com/articles/article_Trouble_CORBA.html |archive-date=3 December 2012 |title=Trouble with CORBA |last=Chappel |first=David |date=May 1998 |access-date=15 March 2010 |publisher=davidchappel.com}}</ref> Much of the criticism of CORBA stems from poor implementations of the standard and not deficiencies of the standard itself. Some of the failures of the standard itself were due to the process by which the CORBA specification was created and the compromises inherent in the politics and business of writing a common standard sourced by many competing implementors. ;Initial implementation incompatibilities :The initial specifications of CORBA defined only the IDL, not the on-the-wire format. This meant that source-code compatibility was the best that was available for several years. With CORBA 2 and later this issue was resolved. ;Location transparency :CORBA's notion of ___location transparency has been criticized; that is, that objects residing in the same [[address space]] and accessible with a simple [[function call]] are treated the same as objects residing elsewhere (different processes on the same machine, or different machines). This is a fundamental design flaw,<ref>{{cite journal|last=Waldo|first=Jim|author2=Geoff Wyant |author3=Ann Wollrath |author4=Sam Kendall |title=A Note on Distributed Computing|journal=Sun Microsystem Laboratories|date=November 1994|url=http://www.cc.gatech.edu/classes/AY2010/cs4210_fall/papers/smli_tr-94-29.pdf|access-date=4 November 2013}}</ref>{{Failed verification|date=November 2017}} as it makes all object access as complex as the most complex case (i.e., remote network call with a wide class of failures that are not possible in local calls). It also hides the inescapable differences between the two classes, making it impossible for applications to select an appropriate use strategy (that is, a call with 1[[µs]] latency and guaranteed return will be used very differently from a call with 1s latency with possible transport failure, in which the delivery status is potentially unknown and might take 30s to time out). ;Design and process deficiencies :The creation of the CORBA standard is also often cited for its process of [[design by committee]]. There was no process to arbitrate between conflicting proposals or to decide on the hierarchy of problems to tackle. Thus the standard was created by taking a union of the features in all proposals with no regard to their coherence.<ref name="ACM_fall"/> This made the specification complex, expensive to implement entirely, and often ambiguous. :A design committee composed of a mixture of implementation vendors and customers created a diverse set of interests. This diversity made difficult a cohesive standard. Standards and interoperability increased competition and eased customers' movement between alternative implementations. This led to much political fighting within the committee and frequent releases of revisions of the CORBA standard that some ORB implementors ensured were difficult to use without proprietary extensions.<ref name="CORBA_trouble"/> Less ethical CORBA vendors encouraged customer lock-in and achieved strong short-term results. Over time the ORB vendors that encourage portability took over market share. {{Citation needed|date=November 2017}} ;Problems with implementations :Through its history, CORBA has been plagued by shortcomings in poor ORB implementations. Unfortunately many of the papers criticizing CORBA as a standard are simply criticisms of a particularly bad CORBA ORB implementation. :CORBA is a comprehensive standard with many features. Few implementations attempt to implement all of the specifications,<ref name="ACM_fall">{{cite journal |first=Michi |last=Henning |url=http://queue.acm.org/detail.cfm?id=1142044 |title=The Rise and Fall of CORBA |publisher=[[Association for Computing Machinery]] |journal=[[ACM Queue]] |volume=4 |issue=5 |date=30 June 2006 |access-date=15 March 2010}}</ref> and initial implementations were incomplete or inadequate. As there were no requirements to provide a reference implementation, members were free to propose features which were never tested for usefulness or implementability. Implementations were further hindered by the general tendency of the standard to be verbose, and the common practice of compromising by adopting the sum of all submitted proposals, which often created APIs that were incoherent and difficult to use, even if the individual proposals were perfectly reasonable.{{Citation needed|date=February 2007}} :Robust implementations of CORBA have been very difficult to acquire in the past, but are now much easier to find. The SUN Java SDK comes with CORBA built-in. Some poorly designed implementations have been found to be complex, slow, incompatible and incomplete. Robust commercial versions began to appear but for significant cost. As good quality free implementations became available the bad commercial implementations died quickly. ;Firewalls :CORBA (more precisely, [[General Inter-ORB Protocol|GIOP]]) is not tied to any particular communications transport. A specialization of GIOP is the Internet Inter-ORB Protocol or IIOP. IIOP uses raw [[TCP/IP]] connections in order to transmit data. :If the client is behind a very restrictive firewall or [[transparent proxy]] server environment that only allows [[HTTP]] connections to the outside through port 80, communication may be impossible, unless the proxy server in question allows the [[Tunneling protocol|HTTP CONNECT]] method or [[SOCKS]] connections as well. At one time, it was difficult even to force implementations to use a single standard port – they tended to pick multiple random ports instead. As of today, current ORBs do have these deficiencies. Due to such difficulties, some users have made increasing use of [[web services]] instead of CORBA. These communicate using [[XML]]/[[SOAP]] via port 80, which is normally left open or filtered through a HTTP proxy inside the organization, for web browsing via HTTP. Recent CORBA implementations, though, support [[Secure Sockets Layer|SSL]] and can be easily configured to work on a single port. Some ORBS, such as [[TAO (software)|TAO]], omniORB and [[JacORB]] also support bidirectional GIOP, which gives CORBA the advantage of being able to use callback communication rather than the polling approach characteristic of web service implementations. Also, most modern firewalls support GIOP & IIOP and are thus CORBA-friendly firewalls. == See also == ===Software engineering=== * [[Component-based software engineering]] * [[Distributed computing]] * [[Portable object (computing)|Portable object]] * [[Service-oriented architecture]] (SOA) ===Component-based software technologies=== * [[Freedesktop.org]] [[D-Bus]] – current open cross-language cross-platform object model * [[GNOME]] [[Bonobo (GNOME)|Bonobo]] – deprecated GNOME cross-language object model * [[KDE]] [[Desktop communication protocol|DCOP]] – deprecated KDE interprocess and software componentry communication system * [[KDE]] [[KDE Platform#KParts|KParts]] – KDE component framework * [[Component Object Model]] (COM) – Microsoft Windows-only cross-language object model * [[Distributed Component Object Model|DCOM]] (Distributed COM) – extension making COM able to work in networks * [[Common Language Infrastructure]] – Current [[.NET Framework|.NET]] cross-language cross-platform object model * [[XPCOM]] (Cross Platform Component Object Model) – developed by Mozilla for applications based on it (e.g. [[Mozilla Application Suite]], [[SeaMonkey]] 1.x) * [[IBM System Object Model]] SOM and DSOM – component systems from IBM used in [[OS/2]] and [[AIX]] * [[Internet Communications Engine]] (ICE) * [[Java remote method invocation]] (Java RMI) * [[Java Platform, Enterprise Edition]] (Java EE) * [[JavaBean]] * [[OpenAIR]] * [[Remote procedure call]] (RPC) * [[Windows Communication Foundation]] (WCF) * [[Software Communications Architecture]] (SCA) – components for embedded systems, cross-language, cross-transport, cross-platform ===Language bindings=== * [[Language binding]] * [[Foreign function interface]] * [[Calling convention]] * [[Dynamic Invocation Interface]] * [[Name mangling]] * [[Application programming interface]] - API * [[Application binary interface]] - ABI * [[Comparison of application virtual machines]] * [[SWIG]] opensource automatic interfaces bindings generator from many languages to many languages == References == {{Reflist}} == Further reading == * {{cite web |url= https://www.omg.org/spec/CORBA/ |title= CORBA |work= Current |series= Specification |publisher= [[Object Management Group|OMG]]}} *{{cite book |first=Robert |last=Orfali |title=The Essential Client/Server Survival Guide |publisher=John Wiley & Sons |isbn=0-471-15325-7 |url=https://archive.org/details/essentialclients00orfa }} *{{cite book |first=Robert |last=Orfali |first2=Dan |last2=Harkey |first3=Jeri |last3=Edwards |title=The Essential Distributed Objects Survival Guide |url=https://archive.org/details/essentialdistrib00orfa |url-access=registration |publisher=John Wiley & Sons |ISBN=0-471-12993-3}} *{{cite book |first=Robert |last=Orfali |first2=Dan |last2=Harkey |title=Client/Server Programming with JAVA and CORBA |publisher=John Wiley & Sons |ISBN=0-471-24578-X |url-access=registration |url=https://archive.org/details/clientserverprog00orfa }} *{{cite book |first=Dirk |last=Slama |first2=Jason |last2=Garbis |first3=Perry |last3=Russell |title=Enterprise CORBA |url=https://archive.org/details/isbn_9780130839633 |url-access=registration |publisher=Prentice Hall |ISBN=0-13-083963-9}} *{{cite book |first=Michi |last=Henning |first2=Steve |last2=Vinoski |title=Advanced CORBA Programming with C++ |url=https://archive.org/details/advancedcorbapro00henn |url-access=registration |publisher=Addison-Wesley |ISBN=0-201-37927-9}} *{{cite book |first=Axel |last=Korthaus |first2=Martin |last2=Schader |first3=Markus |last3=Aleksy |url=http://www.wifo.uni-mannheim.de/CORBA/ |title=Implementing Distributed Systems with Java and CORBA |publisher=Springer |ISBN=3-540-24173-6 |access-date=23 June 2005 |archive-url=https://web.archive.org/web/20051031102447/http://www.wifo.uni-mannheim.de/CORBA/ |archive-date=31 October 2005 |url-status=dead }} *{{cite book |first=Fintan |last=Bolton |title=Pure Corba |publisher=Sams Publishing |ISBN=0-672-31812-1 |url-access=registration |url=https://archive.org/details/purecorba00fint }} *{{cite book |first=Jon |last=Siegel |title=CORBA 3 - Fundamentals and Programming |publisher=John Wiley & Sons |ISBN=0-471-29518-3}} *{{cite book |first=Ron |last=Zahavi |title=Enterprise Application Integration with CORBA: Component and Web-Based Solutions |publisher=John Wiley & Sons |ISBN=0-471-32720-4}} *{{cite book |first=Bret |last=Hartman |first2=hartman |last2=Beznosov |first3=Steve |last3=Vinoski |first4=Donald |last4=Flinn |title=Enterprise Security with EJB and CORBA |publisher=John Wiley & Sons |ISBN=0-471-40131-5}} *{{cite book |first=Thomas J. |last=Mowbray |first2=Ron |last2=Zahavi |title=The Essential Corba: System Integration Using Distributed Objects |url=https://archive.org/details/essentialcorbasy00mowb |url-access=registration |publisher=John Wiley & Sons |ISBN=0-471-10611-9}} *{{cite book |first=Michael |last=Rosen |author-link = Michael Rosen (enterprise architect)|first2=David |last2=Curtis |title=Integrating CORBA and COM Applications |publisher=John Wiley & Sons |ISBN=0-471-19827-7}} *{{cite book |first=Gerald |last=Brose |first2=Andreas |last2=Vogel |first3=Keith |last3=Duddy |title=Java Programming with CORBA |publisher=John Wiley & Sons |ISBN=0-471-37681-7}} *{{cite book |first=John |last=Schettino |first2=Robin S. |last2=Hohman |first3=Liz |last3=O'Hara |title=CORBA For Dummies |publisher=Hungry Minds |ISBN=0-7645-0308-1 |url-access=registration |url=https://archive.org/details/corbafordummies00sche }} *{{cite book |first=Jeremy L. |last=Rosenberger |title=Teach Yourself CORBA in 14 Days |url=https://archive.org/details/teachyourselfcor00rose |url-access=registration |publisher=Sams Publishing |ISBN=0-672-31208-5}} *{{cite book |first=Jon |last=Siegel |title=Quick CORBA 3 |publisher=John Wiley & Sons |ISBN=0-471-38935-8}} *{{cite book |first=Thomas J. |last=Mowbray |first2=Raphael C. |last2=Malveau |title=CORBA Design Patterns |publisher=John Wiley & Sons |ISBN=0-471-15882-8 |url-access=registration |url=https://archive.org/details/corbadesignpatte00mowb }} *{{cite book |first=Robert |last=Orfali |first2=Dan |last2=Harkey |first3=Jeri |last3=Edwards |title=Instant CORBA |url=https://archive.org/details/instantcorba00orfa |url-access=registration |publisher=John Wiley & Sons |ISBN=0-471-18333-4}} * {{cite book |last=Harmon |first=Paul |first2=William |last2=Morrissey |year=1996 |title=The Object Technology Casebook |publisher=John Wiley & Sons |ISBN=0-471-14717-6 |author-link=Paul Harmon (management author) |url-access=registration |url=https://archive.org/details/objecttechnology00harm }} == External links == {{wikibooks|CORBA Programming}} * [http://www.omg.org/spec/CCM/ Official OMG CORBA Components page] * [http://ditec.um.es/~dsevilla/ccm Unofficial CORBA Component Model page] * [https://www.taox11.org/documents/presentations.html Comparing IDL to C++ with IDL to C++11] * [http://queue.acm.org/detail.cfm?id=1388786 Corba: Gone But (Hopefully) Not Forgotten] * [http://www.omg.org/spec/CORBA/ OMG XMI Specification] {{ISO standards}} {{Authority control}} [[Category:Common Object Request Broker Architecture| ]] [[Category:Component-based software engineering]] [[Category:GNOME]] [[Category:Inter-process communication]] [[Category:ISO standards]] [[Category:Object-oriented programming]]'