Postmodernism has petered out – will 'altermodernism' take its place? The Tate showcase is ambitious, just don't look for too much meaning or substance, writes AIDAN DUNNE.

ONE OF THE virtues of the term “relational aesthetics”, coined by French curator and writer Nicolas Bourriaud in the late 1990s, is that it attempted to describe something that was going on in the world of contemporary art. It wasn’t as if Bourriaud, secure in his ivory tower, had come up with a theory of what art should be. Rather he set out to frame an account of what was happening. It’s true that, as one of the founders of the Palais de Tokyo in Paris, which has been labelled, not unreasonably, a kind of laboratory of contemporary art, he was in a position to influence what sort of art would be promoted, but mostly he was trying to make sense of something that was already there.

What was going on, he argued, was a shift in the way that art was conceived, produced and received. Instead of the artist labouring in a studio to produce a finished object that would later be encountered by visitors to a gallery or museum, who might then go away and ponder the meaning of what they had seen, the emphasis had shifted to the shared space of engagement. What mattered was the social and personal interactivity afforded by the cultural process. Nowadays, he said in 2001, the artist is like a social worker and the art object is more a documentation of the work rather than an end point in itself. All of this is evident in the way more and more art hinges on acts of intervention in the social, communal world.

Still, Bourriaud’s concept is slippery. It’s not inherently clear why or exactly what kind of social relations should be so absolutely privileged in the artistic process, as at least one commentator has pointed out. An enormous range of art could be drawn into the relational net, and some of the artists he identified as exemplifying relational aesthetics disagreed with the relevance of the term to their work. At the same time, if his theory is seen as descriptive rather than prescriptive, it really does reflect a major trend in contemporary art. And to that extent he has partly succeeded where a roll-call of illustrious curators, in devising huge, expensive exhibitions with the aim of identifying the next big thing, have not.

Now Bourriaud is working at the Tate in London, where he has curated the fourth Tate Triennial, an ambitious group exhibition designed to showcase cutting-edge art in Britain. But Bourriaud's thesis is that old geographical boundaries have been transcended in contemporary culture, so his show, Altermodern, is truly international in flavour.

Altermodern is, he proposes, the next big thing. We’re all pretty sure that postmodernism has had its day and has petered out, but no one is sure where that leaves us, or what has taken its place.

For some time now the art world has seemed to be in disarray, even in a state of chaos. Bourriaud suggests that a monolithic, primarily western modernism was succeeded by postmodernism, with an emphasis on multiculturalism, origins and identity. What next? Relational aesthetics mapped out an emergent route and now his new coinage, altermodern, specifies the destination. The altermodern is, he says, the 21st century’s “modernity to come” and essentially stems from globalisation. Not so much the big bad wolf of economic globalisation though; it is more the reality of instantaneous communication and information saturation, of permeable borders, of exile and constant travel. The result is a “creolisation” of culture, where translation, multiplicity, rootlessness and nomadism are the norm.

WITH THE WORLD in the grip of a recession, his description of altermodernity may already be out of date, but it’s true that all of the conditions he refers to have existed for some time. Artists on the international circuit, for example, do indeed operate in much the way he describes. Take Franz Ackermann, who is included in his show (and who has shown here at Imma). Ackermann’s frenetically busy painted and constructed installations are about living and coping with constant travel and hyperactive urban environments. Yet he hasn’t quite got beyond conveying a sense of incoherence by being incoherent. More effectively, Walead Beshty ships glass boxes by Fed-Ex and exhibits them as they accumulate damage, in a piece that echoes Marcel Duchamp.

A home-made, DIY approach is part and parcel of the relational aesthetic, and it's evident in Altermodern. Nathaniel Mellors's installation Giantbumis built around a notional scatological fantasy epic, but in a deliberately clumsy, piecemeal way. By any conventional critical standard – in terms of imagination, dialogue, narrative, imagery, production – it's really dreadful, but Mellors and Bourriaud would argue that, by those standards, it's supposed to be dreadful, or it doesn't matter that it is. The same applies to Shezad Dawood's multi-genre film.

The memorably named Spartacus Chetwynd (she adopted the Spartacus herself) has established quite a reputation by staging unruly, improvisatory performance events drawing on pop culture and other references. Hermito's Children, broadcast on stacks of television monitors, is a cheerfully shambolic visualisation of a presumably invented pornographic detective drama.

There is also a great deal of meticulously crafted work on view though. Ruth Ewan’s giant accordion (built not by her but to her specifications) is a fantastic object. Subodh Gupta’s mushroom cloud composed of myriad stainless steel pots is a good coup de théâtre. In many ways Tacita Dean is one of the most traditional artists included, and her powerfully atmospheric, composite work The Russian Ending, features murky, annotated black-and-white enlargements of found postcards depicting unidentified calamities and oddities. They recall the images WG Sebald incorporated in his books, and Bourriaud has specifically cited Sebald as an Altermodern artist. Incidentally, Dean’s obscure title refers to an historical practice on the part of Danish film studios, in catering to a Russian preference for tragic endings.

Katie Paterson’s striking, sombre cosmological chart of dead stars is reminiscent of Vija Celmins’s celestial studies. Darren Almond is travelling around the world photographing the moon, and the fruits of the Chinese stage of his journey are included in the show. They are beautiful, if bland, photographs. Simon Starling (who showed last year in the Limerick City Gallery of Art) includes a typically perverse but intriguing project, displaying three versions of a modernist desk designed, but never built at the time, by Francis Bacon. Starling had three woodworkers build a version on the basis of a photograph of the design sent to them by mobile phone. Lindsay Seers’s autobiographical documentary – or mockumentary – is extremely well done with a rich idea at its core.

Marcus Coates, who is obviously not afraid to be described as mad, is known for his intense, shamanistic performances, in which he imaginatively enters into the world of animal spirits. The piece included, staged in Israel and featuring a parable about the plover, is memorable, but also a bit pompous and patronising. New Yorker Rachel Harrison, who shows a series of thematic photographs from all over the world, together with sculptural constructions and video, is a very interesting artist with great vitality and feeling for materials.

SOMETIMES THE formidable logistics just don’t justify the results. There’s a wan effort by veteran designer of psychedelic light shows Gustav Metzger, and little more than an incredibly laboured pun in a big installation by Joachim Koesters. Research is a buzzword in art these days. Olivia Plender researched a right-wing offshoot of the scouting movement, but she presents her material so ponderously that she is either parodying the style of overly earnest documentaries or is just deeply, genuinely boring. In either case you’re not inclined to stick around. And Charles Avery’s ongoing documentation of an imagined world is not remotely interesting enough.

So, if it's the future, does it work? You'll hardly like everything in Altermodern. But chances are you will like at least some of it a lot. It's relatively coherent, and relatively approachable in comparison to many international exhibitions throughout the rambling saga of postmodernity. The old charge – but it doesn't mean anything – has been levelled at works in Altermodern. But of course they do have meaning, everything does. Meaning is cheap. Meaning gathered into something like an argument, a form that pleases, challenges and intrigues, is much rarer altogether. Bourriaud has been laudably ambitious, and his show is well worth seeing, but it's unlikely to mark a major art-historical shift. It would need more substance for that.

Altermodernis at Tate Britain, Millbank, London, until Apr 26, admission £7.80; www.tate.org.uk/britain/