How do you define the merit of architecture?

Amid the debate about the merits of preserving buildings from the start of Abu Dhabi's boom times, another question is inevitably raised: what structures from the modern era will be deemed noteworthy enough for preservation in another 50 years?
The whims of architectural fashions are fickle enough even now to wonder what will make the cut in 2062.
Take the Aldar headquarters building (aka the Death Star, the Giant Dirham, the Frisbee) beside the motorway at Raha Beach. Completed in 2010, it had won the Building Exchange Conference's award for the best futuristic design two years earlier. Recently anyone flying on Etihad could watch a National Geographic documentary lauding its design and construction as a tribute to Abu Dhabi's vision.
And they could also respond to an online poll in Britain's The Daily Telegraph newspaper, which in February featured the Aldar headquarters among 21 structures selected from across the globe.
And the question posed by the poll? "Are these the ugliest buildings in the world?"
The Aldar headquarters' selection for that list seemed a little mean-spirited, especially since the next candidate in the newspaper's list was the Longaberger Basket Company building in Newark, Ohio. This is a seven-storey structure that is a supersized version of the company's maple-wood basket, complete with a pair of faux-wooden handles soaring into the sky as if it could be collected by a passing giant (and, if the giant had any taste, hurled into a bottomless pit).
But it helps illustrate the entirely subjective nature of assessing architectural merit, which has as much to do with timing as it does anything else.
As the heritage activists of Abu Dhabi are learning, often the biggest hurdle faced by many noteworthy buildings is surviving being one generation old.
Look at many of the world's boomtowns and the ones that have preserved their architecture tend to be those where the booms suddenly ended. Austerity, it turns out, is one of the best architectural preservatives.
San Francisco's stock of ornate Victorian houses survived because the gold ran out and the riches didn't really return until after the Second World War, by which time the Victorian architecture was old enough to be valued.
It was the same in Melbourne, Australia, where a similar gold boom left a legacy of late Victorian villas that were deemed the preserve of the poor until their sudden rehabilitation in the 1980s. Now only the wealthy can afford them.
London's stock of red brick Victorian and Edwardian homes, now treasured, were seen in the 1950s and 1960s as dowdy, dark, cold and old fashioned. But Britain's depleted coffers after the war saved them from being demolished and replaced with concrete brutalist structures of the kind that, in the 1980s and 1990s, were in turn derided but which are now regaining a degree of respect and protection (fans of brutalism can probably thank the efforts of the Luftwaffe rather than aspirational homebuilders for creating many of the building opportunities in London in the post-war period).
All this makes the challenge faced by Abu Dhabi's architectural heritage activists clear: the boom times in the UAE capital are ongoing instead of coming to an abrupt halt like in those other places.
It means out-of-fashion buildings from the 1970s and 1980s - and even the 1990s - are being eyed for demolition and replacement by people who have the means to make it happen.
Which then poses the question of how buildings constructed in the last five years will be seen by the residents of the capital in 2062. One generation on, will they be looking with faint disdain at the Aldar headquarters, the Capital Gate, the Sheikh Zayed Bridge and the Yas Hotel? Or will they be celebrating the architecture that characterised a time when Abu Dhabi went from being "that town near Dubai" to being a city known worldwide in its own right.