In 1774 Edmund Burke explained to his constituents that, should they vote him into the House of Commons, he would act as a trustee of their faith in accordance with his own conscience. He asked them to trust him to do the right thing: The Trustee Model.
This is in contrast to the notion that an MP is a delegate of his constituents, voicing their concerns and voting in a way (s)he believes the majority of the constituents would want. This is sometimes know as The Delegate Model.
Alternatively, if an MP believes that they won their seat because they belong to the party with the winning Manifesto they may act to bring those election pledges into being: The Mandate Model.
Interactive Democracy recognises that MPs are torn between conscience, party and constituents on some issues. Yet they have no simple mechanism for measuring the will of the majority of their constituents and must make assumptions about what they want. ID provides that mechanism and at the same time frees MPs to debate and persuade as their party and conscience dictate.