SOAP
29215
225664156
2008-07-14T20:13:51Z
157.189.2.109
/* External links */
{{OtherUses}}
{{IPstack}}
<!-- Edit the stack image at: Template:IPstack -->
<!-- {{merge|Simple Other Access Points|Talk:SOAP#Merge proposal|date=January 2008}} -->
'''SOAP''' (see [[SOAP#History|below]] for name and origins) is a [[protocol (computing)|protocol]] for exchanging [[XML]]-based messages over [[computer network]]s, normally using [[HyperText Transfer Protocol|HTTP]]/[[HTTPS]]. SOAP forms the foundation layer of the [[web services protocol stack]] providing a basic messaging framework upon which abstract layers can be built.
As a layman's example of how SOAP procedures can be used, a correctly formatted call could be sent to a Web Service enabled web site - for example, a house price database - with the data ranges needed for a search. The site could then return a formatted XML document with all the required results and associated data (prices, location, features, etc). These could then be integrated directly into a third-party site.
There are several different types of messaging patterns in SOAP, but by far the most common is the [[Remote Procedure Call]] (RPC) pattern, in which one network node (the ''client'') sends a request message to another node (the ''server'') and the server immediately sends a response message to the client. SOAP is the successor of [[XML-RPC]], though it borrows its transport and interaction neutrality and the envelope/header/body from elsewhere, probably from [[WDDX]].{{Fact|date=February 2007}}
==History==
'''SOAP''' once stood for 'Simple Object Access Protocol' but this acronym was dropped with Version 1.2 of the standard, as it was considered to be misleading. Version 1.2 became a [[W3C]] Recommendation on [[June 24]] [[2003]]. The acronym is sometimes confused with [[Service-oriented architecture|SOA]], or Service-oriented architecture; however SOAP is quite different from SOA.
SOAP was originally designed by [[Dave Winer]], [[Don Box]], Bob Atkinson, and Mohsen Al-Ghosein in [[1998]], with backing from [[Microsoft]] (where Atkinson and Al-Ghosein worked at the time), as an object-access protocol. The [http://www.w3.org/TR/soap/ SOAP specification] is currently maintained by the [http://www.w3.org/2000/xp/Group/ XML Protocol Working Group] of the [[World Wide Web Consortium]].
==Transport methods==
SOAP makes use of an Internet application layer protocol as a transport protocol. Critics have argued that this is an abuse of such protocols, as it is not their intended purpose and therefore not a role they fulfill well. Backers of SOAP have drawn analogies to successful uses of protocols at various levels for [[Tunneling protocol|tunneling]] other protocols. {{Fact|date=February 2007}}
Both [[SMTP]] and [[HTTP]] are valid application layer protocols used as Transport for SOAP, but [[HTTP]] has gained wider acceptance as it works well with today's Internet infrastructure; specifically, HTTP works well with network [[firewall (networking)|firewalls]]. SOAP may also be used over [[HTTPS]] (which is the same protocol as HTTP at the application level, but uses an encrypted transport protocol underneath) in either simple or mutual authentication; this is the advocated [[WS-I]] method to provide web service security as stated in the [[WS-I Basic Profile]] 1.1. This is a major advantage over other distributed protocols like [[General_Inter-ORB_Protocol|GIOP]]/[[IIOP]] or [[Distributed Component Object Model|DCOM]] which are normally filtered by firewalls. [[XML]] was chosen as the standard message format because of its widespread use by major corporations and [[open source]] development efforts. Additionally, a wide variety of freely available [[software development tool|tools]] significantly eases the transition to a SOAP-based implementation..
The somewhat lengthy [[syntax]] of [[XML]] can be both a benefit and a drawback. While it promotes readability for humans, it can retard processing speed and be cumbersome. For example, [[CORBA]], [[General_Inter-ORB_Protocol|GIOP]], [[Internet Communications Engine|ICE]], and [[Distributed Component Object Model|DCOM]] use much shorter, binary message formats. On the other hand, hardware appliances are available to accelerate processing of [[XML]] messages.<ref>[http://www-306.ibm.com/software/integration/datapower/xa35/ IBM Datapower]</ref><ref>[http://www.research.ibm.com/XML/IBM_Zurich_XML_Accelerator_Engine_paper_2004May04.pdf IBM Zurich XML Accelerator Engine]</ref> [[Binary XML]] is also being explored as a means for streamlining the throughput requirements of XML.
==Technical critique==
Numerous commentators and specialists have discussed the technical advantages and disadvantages of SOAP relative to alternative technologies, and relative to the context of its intended use.
===Advantages===
* Using SOAP over''' HTTP''' allows for easier communication through [[proxy server|proxies]] and [[firewall|firewalls]] than previous remote execution technology.
* SOAP is versatile enough to allow for the use of different transport protocols. The standard stacks use HTTP as a transport protocol, but other protocols are also usable (e.g. SMTP).
* SOAP is platform independent.
* SOAP is language independent.
* SOAP is simple and extensible.
===Disadvantages===
* Because of the verbose XML format, SOAP can be considerably slower than competing [[middleware]] technologies such as [[CORBA]]. This may not be an issue when only small messages are sent.<ref>[http://www-128.ibm.com/developerworks/library/ws-pyth9/ IBM Developer works]</ref> To improve performance for the special case of XML with embedded binary objects, [[MTOM|Message Transmission Optimization Mechanism]] was introduced. Further, to improve the performance of XML in general, there are emerging non-extractive XML processing models, e.g., [[VTD-XML]].
* When relying on [[HTTP]] as a transport protocol and not using [[WS-Addressing]] or an [[Enterprise service bus|ESB]], the roles of the interacting parties are fixed. Only one party (the client) can use the services of the other. Developers must use [[Polling (computer science)|polling]] instead of notification in these common cases.
* Most uses of HTTP as a transport protocol are done in ignorance of how the operation would be modelled in HTTP. This is by design (with analogy to how different protocols sit on top of each other in the IP stack) but the analogy is imperfect (because the application protocols used as transport protocols are not really transport protocols). Because of this, there is no way to know if the method used is appropriate to the operation. This makes good analysis of the operation at the application-protocol level problematic at best with results that are sub-optimal (if the POST-based binding is used for an application which in HTTP would be more naturally modelled as a GET operation).
==Additional information==
*[[SOAP with Attachments]]
*[[SOAP with Attachments API for Java]]
*[http://soa.sys-con.com/read/523481.htm SOAP Over JMS Interoperability]
*[[Web Services Description Language|Web Services Description Language (WSDL)]]
==References==
{{ref-list}}
==External links==
* [http://www.w3.org/TR/soap/ W3C SOAP page]
* [http://www.w3.org/TR/soap12/ SOAP Version 1.2 specification]
* [http://www.w3schools.com/soap/default.asp SOAP Tutorial]
[[Category:World Wide Web Consortium standards]]
[[Category:Application layer protocols]]
[[Category:XML-based standards]]
[[Category:Remote procedure call]]
{{compu-network-stub}}
[[ar:سواب]]
[[bn:সিম্প্ল অবজেক্ট এক্সেস প্রোটকল]]
[[ca:SOAP]]
[[cs:Simple Object Access Protocol]]
[[da:SOAP]]
[[de:SOAP]]
[[es:SOAP]]
[[eo:SOAP]]
[[eu:SOAP]]
[[fa:پروتکل دسترسی آسان به اشیاء]]
[[fr:SOAP]]
[[gl:Simple Object Access Protocol]]
[[ko:SOAP]]
[[id:SOAP]]
[[is:SOAP]]
[[it:SOAP]]
[[he:SOAP]]
[[hu:SOAP]]
[[nl:Simple Object Access Protocol]]
[[ja:SOAP (プロトコル)]]
[[pl:SOAP]]
[[pt:SOAP]]
[[ru:SOAP]]
[[sk:Simple Object Access Protocol]]
[[fi:SOAP]]
[[sv:SOAP]]
[[uk:SOAP]]
[[zh:SOAP]]