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| ASN.1简介(4) |
| 作者： 文章出处：http://asn1.elibel.tm.fr/en/
发布时间：2005-06-25 点击：
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ASN.1 was first standardized in 1984 by the CCITT (International Telegraph and Telephone Consultative Committee, now called ITU-T, International Telecommunication Union - Telecommunication Standardization Sector) under the name "X.409 Recommendation". A little later, ISO (International Organization for Standardization) chose to adopt this notation and split this recommendation into two separate documents: the abstract syntax (ASN.1) and the encoding rules (BER). In 1985, the CCITT decided to collaborate with ISO on these two documents.
In 1987, ISO published these documents as 8824 and 8825 (only three new types of character strings are added). In 1988, ISO merged with the IEC (International Electrotechnical Commission) forming a joint technical committee called ISO/IEC JTC 1, which is now in charge of the ASN.1 standard.
For its Blue Book, in 1989, the CCITT published the X.208 and X.209 recommendations: a new release for the ASN.1 standard, which was provided with extensions resulting from a common work with the JTC 1.
For the next version called ASN.1:1994 (available since 1995), the ISO 8824 standard was split into four parts:
The first part improves ASN.1:1990 standard: the macro notation and the type ANY DEFINED BY disappear, they are replaced by the concept of information object classes; automatic tagging on a whole module becomes possible and type parameterization and multi-byte characters emerge.
As far as encoding rules are concerned, ISO 8825 standard was split into two parts:
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It is this ASN.1:2002 edition which is, from now on, strongly recommended. The 1990-release is no longer available in the near future.
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In April 1999, a new standard called ASN.1:1997 was released. But for a few addenda within the notation, the modifications were mainly editorial and consist in integrating amendments and technical corrigenda issued between 1994 and 1997.
The ASN.1 Committee has been working on a new release of the standard which was published in 2002. This release integrates all the technical corrigenda and amendments that have been issued against the 1997 release. It also includes a support for XML through the XML encoding rules (XER) and the mapping of XML Schemas into ASN.1 moduls.
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Presented during the January 1999 ASN.1 meeting, the encoding control notation (ECN) allows specifiers to define their own encoding rules by referencing standardized encoding rules and modifying some of their characteristics, or even to set up completely new ones.
ASN.1 has a long record of accomplishment, having been in use since 1984. It has evolved over time to meet industry needs, such as PER support for the bandwidth-constrained wireless industry and XML support for easy use of common Web browsers. |
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