O S I data communication for dealing with abstract syntaxes which are and are not preliminarily negotiated

Abstract

Being operable as a presentation layer defined by the International Standard ISO 7498, each data communication system comprises (A) a syntax transforming unit and (B) an abstract syntax storing unit besides (a) an application program unit for producing and receiving abstract syntaxes descriptive of data according to the International Standard ISO 8824 and (b) a sending and receiving unit for sending and receiving trasfer syntaxes to and from at least one counterpart system. Before carrying out data transfer, negotiation is had in the known manner to decide a set of abstract syntaxes, which can be used in the data transfer and are herein called negotiated syntaxes and encoded by the transforming unit into primary transfer syntaxes as herein called with these transfer syntaxes accompanied by first information. The application program unit may produce different syntaxes which are the abstract syntaxes other than the negotiated syntaxes. Even in this event, the transforming unit encodes the different syntaxes into what are herein called secondary transfer syntaxes with these transfer syntaxes accompanied by second information. When supplied with each secondary transfer syntax and the second information from the counterpart system, the storing unit stores the second information in the transforming unit. This enables the transforming unit to refer to the second information like usual reference to the first information and to decode the secondary transfer syntax in question into a reproduction of one of the different syntaxes that is used in the counterpart system.

Dependencies are inferred from the claim text.