Imagine a city where your car tells you the location of the nearest vacant parking space. Or a city where you are notified as soon as a neighbour submits a planning application. Where up-to-the-minute listings of every cultural event and venue are available - all the time, wherever you happen to be. Imagine if you could discover the asking price of the cheapest two-bedroom home that has just gone on sale, in the catchment area that will guarantee your child a place at the best-performing school.
This is the thinking that led to the United Kingdom's first Open-data Cities Conference, which will be held at Brighton Dome Corn Exchange on Friday, April 20.
It's not technology that is holding us up. Although the rate of change will be greater as we progress towards ubiquitous, free, high-speed internet access available to everybody via a myriad devices.
For open-data cities to become reality, we don't have to wait until connectivity - and the "connectedness" it engenders - is the air we breathe.
Nor do we have to wait for the "internet of things", of which all kinds of objects - not just computers, tablets and phones - will be a part.
Emerging technologies associated with a semantic web of data are already sufficient to power innovative applications, services, and enterprises that will compete and combine to meet the needs of communities in the 21st century.
It is lack of data that will limit our ambitions. It is a dearth of data that risks keeping our cities in the slow lane to the future.
In a post-digital era - when the differentiation between analogue and digital, between "real" and "virtual", will finally be blurred beyond relevance - we will live in the age of data.
Even now, data is everywhere, all the time. It defines, describes and determines the world we live in.
The more data that is released - without strings attached, in machine-readable and non-proprietary "open" formats - the more likely it is that businesses and developers will use it to build the applications and services that world-class cities need.
Of course, I'm not urging the release of personal data relating to identifiable individuals.
The civic data I'm talking about is data about schools, catchment areas, and property prices; about bus times and bus-stops, taxi ranks, car parks, and traffic congestion; about energy use, CO2 emissions, and carbon footprints.
The crucibles for global change will be "open-data" cities - cities which self-consciously and collectively decide to make available unimaginable quantities of data, openly and freely.