SOAP (Simple Object Access Protocol) is a protocol defined originally by Microsoft and standardized by the W3C. It make use of XML, which defines the mechanisms for exchanging information between clients and web service providers.
The transport mechanism used for SOAP messages can be HTTP, SMTP, FTP, etc..
There are SOAP libraries available for many languages, including Perl, C, C++, C#, Python, Java, Visual Basic/.NET, PHP, Ruby, etc.
Modes of communication
SOAP supports many data types as parameters:
SOAP defines an mechanism for associative arrays to notify the occurence of errors.