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4.4.4.3 System and Device Data
Most of the system and device data messages can be represented with the Condition,
Variable and the File Management Dialogues as explained in the previous sections.
However,
Program Execution Dialogue is the most suitable for Device Command
messages. A Program Execution is an action or set of actions to be carried out by the
CID. The format of this dialogue is illustrated in Exhibit 4.4-7.
Exhibit 4.4-7 Program Execution Dialogue
Field Description of Field/Attributes
1 Message Header
2 Program Needing Input
3 Program Producing Output
4 Program Name
5 Parameter List
Program Name is the same format as the File Name explained in the previous section.
The Parameter List consists of parameters that are unspecified and in ASCII Text
forma t.
4.4.4.4 Event Data
The event data messages are represented by Condition Dialogues (Appendix B).
4.4.4.5 Peer to Peer Clearing & Settlement
The VEI does not define any clearing and settlement related messages.
4. 4.5 Data Elements
Wh ile V EI was not designed with smart cards in mind, it is a flexible protocol and can
be extended to include smart card related data elements. It is also possible to define
implementation
specific data types within the protocol when used within a closed
system; although the greatest benefit is obtained by using VEI in its standard identifiers.
4.4.6 Message Sequences
The VEI provides a simple structure of dialogue exchanges between a requester and a
responder. A dialog consists of a request message, a response message( s) and
sometimes
an acknowledgement of the response(s). A request message with or without
data may require a response at the discretion of the requester. A response message that
contains data may require an acknowledgement, at the discretion of the responder.
However,
some responses contain no data and act as acknowledgements. In this case
no
separate acknowledgement message is required.
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