Some intriguing design-writ-large ideas about cities qua applications. Cities, like other things we come upon in daily life, should just work:

Given any new city, there are certain things that should be easy for tourists to comprehend without assistance. These things might include: how and when to use the subway or bus, how and where to buy fares for public transportation, how to make a call at a public telephone, how and where to flag a taxi, what to expect upon entering and leaving the airport, how and where to find postal services, how and where to find a police station, et cetera.