This mapping takes as input a schema written in XML Schema and produces an ASN.1 module containing a set of type definitions (and, optionally, an XER encoding instruction section to keep the same XML encoding, if needed), in such a way that there is a one-to-one correspondence between ASN.1 abstract values and valid XML instances. This technique can be applied to any given XML application language.
ASN.1 standardized encoding rules such as DER (a canonical encoding that allows digital signatures and encryption, for example) or PER (to very efficiently transmit data over a radio channel, for example) can then be used as well as associated ASN.1 tools, or even specific encoding rules that are described in ECN.
This mapping is defined in a standard named ITU-T X.694 | ISO/IEC 8825-5 "Mapping W3C XML Schema definitions into ASN.1".

• Download the standard [pdf]

One big benefit of using a binary encoding is speed. Decoding a binary stream improves performance. Another benefit is size: a binary encoding may save up to 80% or even more relative to corresponding XML text. It is even possible to reduce further with additional redundancy compression. The advantage being that the redundancy-based compression operates on less data. Thus it is possible to process redundancy-compressed PER faster than the XML.
The translation of XML Schema datatypes into ASN.1 types and subtypes constraints increases the relative performance gain when a PER encoding is used.
Some compression results are given in OSS Nokalva's position paper at the W3C Workshop on Binary Interchange of XML Information Item Sets (Sept. 24-26, 2003).

• Performance of OSS Nokalva's XSD tools[txt]
• Average perf. of OSS Nokalva's XSD tools [txt]
• Benefits of binary encoding rules

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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