Information Technology Reference
In-Depth Information
infrastructure
An announcement is made up of two
signals, a request at the initiator,
then an indication at the responder.
req
uest
signal
time
indic
ation
signal
initiator
responder
An interrogation is made up of four
signals; a request and then an indi-
cation pass the operation from the
initiator to the responder; later, a
response and then a confirmation
pass the termination from the re-
sponder to the initiator.
req
uest
signal
indic
ation
signal
resp
o
nse
signal
conrm
signal
initiator
responder
A stream flow involves a sequence of
signals from the producer, resulting
in a sequence of signals to the con-
sumer; each signal gives a sample
from the continuous flow; depend-
ing on the properties of the stream
binding, there may or may not be a
one-to-one relationship between the
signals in these two sequences.
ow s
ample
signal
ow s
ample
signal
ow s
ample
signal
consumer
producer
FIGURE 4.3: Expressing operations and stream flows in terms of signals.
The RM-ODP provides various types of interactions to enable designers to be
precise at any required level. One example is the way that an operation can
be refined into the set of atomic signals describing the individual interactions
happening during the operation's invocation and termination. Another is the
way a complex event distribution system can be modelled as a compound
binding managing sequences of announcements, abstracting away from all the
low-level details involved in the communications between the objects involved.
The linkage of separate event management domains can then be modelled as
a concatenation of compound bindings.
Finally, streams and their component flows are used to model continuous
transfers of information, such as those used for exchanging videos and other
kinds of multimedia streams. You can think of receiving a YouTube video or
an internet radio broadcast as examples of this kind of interaction. A flow is a
continuous transfer of typed information in one direction over a period of time.
Flows can also be used to represent regular data flows, such as monitoring
reports or the continuous flow of periodic sensor readings in a process control
application, without explicit modelling of the steady sequence of messages
involved.
Properties of various kinds of continuous media are specified by
