"We think that there are inherent advantages to the direct model and we don't expect that to change over time."

Dell's direct model does have limitations.

"The direct model is the strongest in terms of customer loyalty," he said.

"The direct model has been a revolution, but it is not a religion," he wrote.

"The direct model has been a revolution, but not a religion," read a copy of the memo seen by Reuters.

Hunter also developed a direct instructional model and elements of effective instruction.

Dell's direct model came under pressure as the market for PCs shifted to notebooks from desktops last year.

But his most direct model was the Ensemble Aleph, a Parisian chamber group.

An assembly language is not so much a paradigm as a direct model of an underlying machine architecture.

Whether it is invitation model or direct model, the abuser is not included in the decision making process for planning the intervention.