OSI/MHS P7 Application Programmatic Interface (P7 API) Manual

Glossary
OSI/MHS P7 Application Programmatic Interface (P7 API) Manual—424825-001
Glossary-25
service
service. A set of primitives (operations) that an OSI layer provides to the layer above it. The
service defines what operations the layer can perform on behalf of its users, but not how
these operations are implemented. A service relates to an interface between two layers,
with the lower layer being the service provider and the upper layer being the service
user. See also protocol.
The GPI and P7 API are examples of services available to applications. In both cases,
the service consists of a process and the library procedures that provide the application
interface to that process.
service access point. See SAP.
service element. In OSI, a feature or function defined as part of a service.
service primitive. In OSI, an abstract, implementation-independent interaction between a
service user and a service provider. Service primitives describe the sequences of events
between adjacent layers that occur through the service access point (SAP). There are
four types of service primitives; see confirm primitive, indication primitive, request
primitive, or response primitive.
session. A temporary logical connection between a user and a software product, or between
communicating processes.
In the GPI, an interaction between a client program and the GPI, established when a
client program successfully calls the GPI_OPEN_ procedure. Once a session is
established, the client program can request GPI services by calling other GPI
procedures. A session is ended by calling the GPI_CLOSE_ procedure.
In the P7 API, an interaction between a client program and an LO group, established
when a client program successfully calls the LOS_OPEN_ procedure. Once a session is
established, the client program can request P7 operations by calling other P7 API
procedures. A session is ended by calling the LOS_CLOSE_ procedure.
session identifier. A designator generated by the GPI when the client program establishes a
session and used by the program to indicate which session is requesting a GPI service.
Session Layer. Layer 5 in the OSI Reference Model. It allows the setup and termination of
sessions and controls communication sessions between nodes on the network.
session selector. See SSEL.
simple token. In DSM programmatic interfaces, a token consisting of a token code and a
value that is either a single elementary field, such as an integer or a character string, or a
fixed (nonextensible) structure. See also extensible structured token.
single-valued attribute. An attribute that has only one value.
site update tape. See SUT.
SNPA (subnetwork point of attachment). A real, physical address, identifying the point of
attachment to a subnetwork.