OSI/AS Programming Manual

OSI Upper-Layer Concepts
APS Procedures Programming Concepts
056783 Tandem Computers Incorporated 2–19
For the ACSE presentation context, OSI/AS sets the the following values in the
presentation context definition result list:
The result is set to indicate acceptance of the proposed presentation context.
The transfer syntax name is set to the value for ASN.1 BER.
The reason is set to no value.
For each element in the presentation context definition result list in the indication, you
must include a corresponding element in the response.
In a Connect Response. When you receive the presentation context definition list in a
presentation or ACSE connect indication, you must set the number of elements in the
presentation context definition result list in your connect response to the same number
that appears in that structure in the connect indication. Each element in the
presentation context definition list has a corresponding element in the presentation
context definition result list; you must preserve the order of the elements. For each
element, you must set the following values in the presentation context definition result
list:
Set the result to either accept or reject the presentation context.
If you choose to accept the presentation context, set the transfer syntax name to
one of the names proposed in the presentation context. If you reject the
presentation context, you need not set the transfer syntax name.
If you are rejecting the presentation context, set the reason to a value.
In a Connect Confirm. OSI/AS sets the presentation context definition result list for a
connect confirm exactly as it was set by the remote system.
Use of the Presentation Context Identifier (PCID)
The PCID is used to identify a presentation data context—or a presentation data value
(PDV)—for data transfer to and from OSI/AS. For inbound presentation data,
OSI/AS sets the PCID. For outbound presentation data, you must set the PCID.
Encoding User Data
Users of OSI/AS must encode their own abstract syntaxes. All user data sent on an
OSI/AS presentation connection must already be encoded in the negotiated transfer
syntax. This rule includes any EXTERNAL declarations or SEQUENCE OF
EXTERNAL declarations that may exist within the API user’s abstract syntax. For
more information about encoding user data see “Sending and Receiving User Data,”
later in this section.