They are
so-called atomic object fl ow ports , shown by the directional arrow ( Figure 2.76 ).
Technically the protocol between the card reader and the customer card runs
over an energy fi eld emitted by the card reader. That ??™ s the same fi eld that feeds
the card with energy. The energy fi eld is modulated appropriately to ensure that
information can be transmitted.
The data exchanged between the customer card and the card reader corresponds
to a request/reply scheme. The ports used here transport not only data??”they also
offer or request services. This means that they are standard ports that are specifi ed
in more detail over interfaces. The interface between the card reader and a customer
card is called ICustomerCard ( Figure 2.76 ). 18 The ??? grabber ??? symbol shows that the
service is requested, while the ??? lollipop ??? symbol means that a service is provided.
We have modeled two ports in total: an object fl ow port for the energy fl ow
and a standard port for the protocol. The reason is that we are looking at two layers,
the application layer (protocol) and the transport layer (energy fi eld).
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