====================
V E N D O R    A P I
====================

When we start the system, API loads all vendor data, and then provides
these data to other modules. Also, it supports the following run-time
modifications to the vendor description and list of current orders.

() Add a new vendor. We specify the vendor name, and we may optionally
specify its id; if an id is unspecified, API assigns an id.

() Delete a vendor; we specify the vendor by either name or id.

() Change the value of the "All Vendors" flag.

() Change an entry in the cost table, that is, update the cost entry
for a specific vendor and item type; this entry may be "Indefinite,"
"Absent," "Unknown," or a numeric cost.

() Add an order to the list of current orders; we specify an order by
vendor, service property, item type, number of items, room, start, and
duration. The system computes the other elements of the order, which
are event id and overall cost.

() Remove an order from the list of current orders; we specify the
order by event id and service property or, alternatively, by vendor,
item type, room, start, and duration.