Object "Zone" with attributes code, name and currencyISO (3 letter iso code for currency of the zone)
Object "Period" with startDate and stopDate
Object "FXRate" with rate (decimal number) and currencyISO, linked to 1 Zone and 1 Period. The rate is the conversion rate from the zone currency to the currencyISO.
Object "Tax" with rate (decimal number), linked to 1 Zone and 1 Period
issue #1 : project structure, object model and database created