[voice interaction CG] example travel planning use case for IPA

This is a travel planning use case, which goes along with the diagram that
Dirk sent earlier
(https://lists.w3.org/Archives/Public/public-voiceinteraction/2019Sep/0003.h
tml).

Looking forward to your comments!

Travel Planning

A user would like to plan a trip to an international conference and she
needs visa information and airline reservations. 

She starts by asking a general purpose assistant ("IPA Service", on the left
of the diagram) about what the visa requirements are for her situation. For
a common situation, such as citizens of the EU traveling to the United
States, the IPA is able to answer the question directly by getting the
information from a web service that it knows about. This could be one of its
dialogs 1-n. However, for less common situations (for example, a citizen of
South Africa traveling to Japan), the generic IPA will try to identify a
visa expert assistant application from the dialog registry. If it finds one,
it will connect the user with the visa expert, one of the IPA providers on
the right side. The visa expert will then engage in a dialog with the user
to find out the dates and purposes of travel and will inform the user of the
visa process. 

Once the user has found out about the visa, she tells the IPA that she wants
to make airline reservations. If she wants to use a particular service, or
use a particular airline, she would say something like "I want to book a
flight on American". The IPA will then either connect the user with
American's IPA or, if American doesn't have an IPA, will inform the user of
that fact. On the other hand, if the user doesn't specify an airline, the
IPA will find a general flight search IPA from its registry and connect the
user with the IPA for that flight search service.  The flight search IPA
will then interact with the user to find appropriate flights. 

A similar process would be repeated if the user wants to book a hotel, find
a rental car, find out about local attractions in the destination city, etc.
Booking a hotel could also involve interacting with the conference's IPA to
find out about a designated conference hotel or special rates. 

This leaves open the question of how much the IPA Service keeps track of the
interactions with the other IPA's. For example, does it add the user's
travel schedule to her calendar after the use picks her flights? I see this
as out of scope for standardization since I think it's a specific capability
of the IPA Service. However, a possible point of standardization could be an
API from an IPA Provider that sends information about the interaction with
the IPA Provider back to the IPA Service, which could then do whatever it
wants with it, for example, adding information to the user's calendar, or
simply logging it.