A SOAP message is an XML document, which is essentially just text. Unicode characters are the only kind of data that can be exchanged using SOAP. This restriction is not a problem in most cases, because W3C's XML schema allows us to exchange a fairly rich set of typed data:
date, and so on. In some cases, however, you may need to convey binary data in SOAP messages. For example, you may want to send a SOAP message that contains a JPEG image or a document that uses a proprietary format such as PDF. SOAP Messages with Attachments (SwA) provides a mechanism to “attach” binary data to a SOAP message without converting binary data to ASCII characters using Base64 encoding.
SwA is certainly one ...