Fast Infoset

Fast Infoset (or FI) is an international standard that specifies a binary encoding format for the XML Information Set (XML Infoset) as an alternative to the XML document format. It aims to provide more efficient serialization than the text-based XML format. Fast Infoset (or FI) is an international standard that specifies a binary encoding format for the XML Information Set (XML Infoset) as an alternative to the XML document format. It aims to provide more efficient serialization than the text-based XML format. FI is effectively a lossless compression, analogous to gzip, for XML, except that while the original formatting is lost, no information is lost in the conversion from XML to FI, and back to XML. While the purpose of compression is to reduce physical data size, FI aims to optimize both document size and processing performance. The Fast Infoset specification is defined by both the ITU-T and the ISO standards bodies. FI is officially defined in ITU-T Rec. X.891 and ISO/IEC 24824-1, and entitled Fast Infoset. The standard was published by ITU-T on May 14, 2005, and by ISO on May 4, 2007. The Fast Infoset standard document can be downloaded from the ITU website. Though the document does not assert intellectual property (IP) restrictions on implementation or use, page ii warns that it has received notices and the subject may not be completely free of IP assertions. A common misconception is that FI requires ASN.1 tool support. Although the formal specification uses ASN.1 notation, the standard includes Encoding Control Notation (ECN) and ASN.1 tools are not required by implementations. An alternative to FI is FleXPath. The underlying file format is ASN.1, with tag/length/value blocks. Text values of attributes and elements are stored with length prefixes rather than end delimiters, and data segments do not require escapement for special characters. The equivalent of end tags ('terminators') are needed only at the end of a list of child-elements. Binary data is transmitted in native format, and need not be converted to a transmission format such as base64.