Gill Robinson, the senior official in charge in the Scottish Executive Education Department, said the extent to which all parts of the curriculum helped create successful learners, confident individuals, responsible citizens and effective contributors to society was being used as a "winnowing tool" to decide what should stay and what should go.
But Dr Robinson emphasised that the process would eventually produce a curriculum that would look largely familiar.
The reformers are working to an exacting timetable, which will see a start to implementing some of the changes from 2007. Dr Robinson said: "We have to consider which changes can be implemented quickly and what requires more thinking, including the involvement of teachers."
Maggi Allan, South Lanarkshire's former education director, who chairs the programme board for the curricular changes, promised preliminary guidance would be issued in the autumn.
It would not be the polished article, Mrs Allan predicted "but a start to a period of engagement with teachers and others". The outcome of that would lead to a process of "refinement" leading into 2006, plans to organise continuing professional development for implementation in 2006-07 and implementation from the following year on.
At the moment, the programme board was at "the reflection stage".
Mrs Allan cited David Hopkins, the American academic, who said that "teaching is what gives the curriculum its power".
She added: "The imagination and creativity of teachers applied to the guidance will be essential. Otherwise, we will not realise the ambitions contained in A Curriculum for Excellence."