Soap Interface

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 other protocols.[citation needed]

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 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, see [2]. This is a major advantage over other distributed protocols like GIOP/IIOP or 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 tools significantly eases the transition to a SOAP-based implementation..

The somewhat lengthy syntax of XML can be both a benefit and a drawback. Its format is possible for humans to read, but can be complex and can have slow processing times. For example, CORBA, GIOP, ICE, and DCOM use much shorter, binary message formats. On the other hand, hardware appliances are available to accelerate processing of XML messages. [3][4]. Binary XML is also being explored as a means for streamlining the throughput requirements of XML.