ITU-T Rec. X.891 | ISO/IEC 24824-1 (Fast Infoset) is an approved ITU-T Recommendation as of 14 May 2005
Unfortunately the specification is not available publicly. However, it is possible to access the specification from:
The ITU-T if you or your company is an ITU-T sector member, or a Study Group 17 associate member; or from
Your ISO National Body.
A document based on Annex D of ITU-T Rec. X.891 | ISO/IEC 24824-1 has been published that presents examples of encoding XML infosets as fast infoset documents.
Relevant to the Fast Infoset specification are two further specifications under development:
Fast Web Services specifies alternative binary encodings for SOAP messages without the need to modify WSDL service descriptions (the SOAP binding and ports do not need to be augmented with new bindings and ports). Fast Infoset may be used in conjunction with an optimized binary encoding of SOAP 1.2 messages (referred to as ASN.1 SOAP messages) or for the serialization of SOAP message infosets (SOAP 1.1 or SOAP 1.2) as fast infoset documents.
Security in Fast Infoset and Fast Web Services is a new proposed work item that aims to specify how standard XML security solutions, such as XML Signature, XML Encryption and SOAP Message Security, may be applied to Fast Infoset and Fast Web Services.