All development, unless specifically exempted under planning legislation, requires planning permission. If any question arises in a particular case as to what does or does not constitute development or exempted development, the question may be referred to An Bord Pleanála for a decision. A number of classes of exempted development are set out in the second schedule to the Local Government (Planning and Development) Regulations, 1994, which provide for certain types of mobile structures to be exempt from the requirement to obtain planning permission.