Some constitutions or fundamental laws provide for a head of state who is not only in theory but in practice chief executive, operating separately from, and independent from, the legislature. This system is known as a "presidential system" and sometimes called the "imperial model", because the executive officials of the government are answerable solely and exclusively to a presiding, acting head of state, and is selected by and on occasion dismissed by the head of state without reference to the legislature. It is notable that some presidential systems, while not providing for collective executive accountability to the legislature, may require legislative approval for individuals prior to their assumption of cabinet office and empower the legislature to remove a president from office (for example, in the United States of America). In this case the debate centers on confirming them into office, not removing them from office, and does not involve the power to reject or approve proposed cabinet members "en bloc", so accountability does not operate in the same sense understood as a parliamentary system.