AML KDT750 Price Verification System - Manual (Page 14)

KDT750 APL Guide
2 - 5
Lookup Reply from Server to Client
In response to a lookup request, the server should reply with meaningful data. In the most
basic of situations, the server will lookup the given data in a retail price database and reply
with the price of the item to be drawn on the LCD.
Figure 2.2 - Example Lookup Reply Screen
A server reply, like a client request, uses 'ITEM=VALUE' elements, but unlike the request, a
reply payload will typically contain multiple pairs. Each ITEM=VALUE pair will denote an
action that the client device should take (i.e., Turning on a digital output) or a text based
field that should be drawn on the LCD screen.
In the example lookup screen above, two output fields are present: one containing the price
(12.99) and the other containing the description (Designer Flower Pot...). The text at the top of
the screen is part of the background image and is not being actively drawn by APL.
Output Pairs and Action Pairs
Normally, in a lookup reply, the ITEM element corresponds to a text field on the screen and
the VALUE element to the text that should be displayed. Each valid element pair received
from the server will be drawn on the KDT750 LCD as a new text field. These output pairs can
have any non-restricted ITEM name as long as it contains only alpha-numeric characters.
This ITEM name is only used internally and must be unique.
A restricted ITEM name is one that is used for a special purpose action (turning on a digital