Syntax converting apparatus for decomposing different portions of a data string differently depending on whether a data string is an external type data string

摘要

A syntax converting apparatus performs conversions between an abstract syntax and a transfer syntax in a presentation layer, defined by an Open Systems Interconnection (OSI). The presentation layer determines the syntax, which describes application processes, and exchanges this syntax with a syntax to be transferred. The syntax converting apparatus is capable of separately decomposing presentation protocol data units (PDUs), which are defined by two different standards, for example, Standard x and Standard y. This is accomplished using a decoding and a decomposing unit in the presentation layer. The decoding unit decodes data strings encoded in accordance with ISO 8825 ASN.1 Basic Encoding Rules, and the decomposing unit decomposes this decoded data with each of the protocol specification units, describing the abstract syntax thereof.