Hopes of a breakthrough in the Belfast peace process negotiations now seem to turn on the practical definition of any IRA commitment to see its arms put finally and permanently beyond use.
The existing schemes established in law under the terms of the Belfast Agreement provide for the handing over of paramilitary weapons to the International Decommissioning Commission or self-destruction of weapons by the armed groups under the commission's supervision.
However, the renewed London/Dublin push for a compromise permitting the restoration of the Northern Ireland Executive seems to have marked a clear shift away from the original decommissioning concept.
As the Taoiseach, Mr Ahern, and the British Prime Minister, Mr Tony Blair, prepare for another marathon session of talks with the Ulster Unionists, Sinn Fein and the SDLP today, it is believed attention is focusing on how weapons could, at least initially, be put beyond use in secure or secured arms dumps.
Official sources maintain the two governments do not yet know if the IRA is prepared to go beyond the terms of its February 11th statement to Gen John de Chastelain to embrace the concept of putting weapons beyond use.
However, it is accepted that if an appropriate form of words is forthcoming, everything in the present negotiation will turn on definition.
It seems clear that London has now been persuaded that the republican leadership is unable to deliver a timetable for actual decommissioning. This immediately identifies one potential obstacle to any attempt by Mr David Trimble to swing the Ulster Unionist Council behind any new deal.
One senior unionist politician said last night: "I don't believe any of it. Why would they [the IRA] be prepared to give something now which they refused to give in February? But if there is no timetable, where is the clarity and the certainty?"
Beyond that, key questions being identified by political insiders include:
whether the putting of weapons beyond use would be an entirely voluntary operation, to be conducted by the paramilitaries themselves and taken by the other parties on trust;
or whether they would agree inventories with, and have locations identified by, the international commission or some other outside agency as part of a verification process;
and how dumps would be deemed secure and whether they would be subject to physical or electronic monitoring.
Given agreement on the substantive issue of weapons, talks insiders say there would be little difficulty finessing the sequencing of statements, covering issues such as the timetable for the restoration of the institutions of government and the putative British programme for demilitarisation in Northern Ireland.
Yet, the arms issue apart, two other key issues loom over today's negotiations. Despite firm opposition from the Irish Government, the SDLP and Sinn Fein, unionist politicians still appear confident they can win significant concessions from Mr Blair on the detail and timing of key RUC reforms.
In addition, it is believed Dublin - which opposed the suspension of the Executive last February - is determined that the question of default mechanisms governing any future suspension must be addressed.
However, informed sources say Mr Trimble is unlikely to accept any deal involving a British commitment never again to suspend the Executive or Assembly unilaterally on the basis that this would effectively place the North's institutions under joint London/Dublin authority.