Fast Infoset
ITU-T X.891 | ISO/IEC 24824-1 (Fast Infoset) specifies
a representation of an instance of the W3C XML Information Set using binary encodings.
These binary encodings are specified using the ASN.1 notation and the ASN.1 Encoding
Control Notation (ECN). The Fast Infoset standard
can be downloaded for free from
the ITU-T website.
The Fast Infoset technology provides an alternative to W3C XML syntax as a means
of representing instances of the W3C XML Information Set. This representation generally
provides smaller encoding sizes and faster processing than a W3C XML representation.
Fast Infoset specifies the use of several techniques that minimize the size of the
encodings (called fast infoset documents) and that maximize the speed of creating
and processing fast infoset documents. These techniques include the use of dynamic
tables (for both character strings and qualified names), initial vocabularies, and
external vocabularies.
Some compression results are published by the open
source Fast Infoset project (parsing
performance, size performance).
Note that these tests don't use any of the so-called Fast Infoset advanced features
which allow for the use of external information (e.g., schema) to employ better
representations for "text" nodes (e.g., IEEE float for xsd:float, etc.).
Using those features, the performance gains can be significantly better
The ASN.1 Schema for the XML information set provides the capability to encode XML
content that is not described by a schema. It defines an alternative to XML 1.0
serialization and, like the ASN.1 Schema for SOAP, ensures the application of a
consistent encoding technology.
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Some related projects and articles:
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Use cases
Fast Infoset has been
adopted by the Web3D community because
it meets their requirements for the encoding of X3D documents.
Here are some explicit use cases as documented by the
W3C XML Binary Characterization (XBC) working group:
Other possible application domains are:
See also the thesis "Analysis
of Binary XML Suitability for NATO Tactical Messaging" by Matthew
E. Bayer (Sept. 2005).
In general Fast Infoset can be used when it is necessary to retain the XML property
of self-description (or the structure) and one requires:
- a boost to parsing speed; and
- a moderate reduction in document size..
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Fast Infoset security
The ASN.1 Group has begun to work on a new ITU-T Recommendation | International
Standard, entitled "Information Technology - Generic Applications of ASN.1 -
Fast Infoset and Fast Web Services Security, that will specify the application
of standard security methods to the Fast Infoset specification.
In order for applications to apply standard security methods to the Fast Infoset
specification, it is necessary to specify transformations to be applied to fast
infoset documents (or parts of them) to support the application of those security
methods.
The scope of the work includes the following:
- specification of a canonical form for fast infoset documents;
- specification of an encryptable form for fast infoset documents;
- use of a fast infoset document canonical form to support XML Signature Syntax and
Processing for the signing of fast infoset documents or parts of them;
- use of a fast infoset encryptable form to support XML Encryption Syntax and Processing
for the encryption of fast infoset documents or parts of them.
ITU-T X.893 | ISO/IEC 24824-3 was approved on May 2007.
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ASN.1 Mailing list
Any questions related to ASN.1/XML (but not to any particular ASN.1 tool) can be
sent to asn1@asn1.org.
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