The number of items should be low, so that the user does not need to scroll inorder to see all of them.Functions should not sometimes occur in main level and at other times in asubmenu. Items that are in a submenu should always be found in the samesubmenu.Only one submenu level is allowed, that is, a submenu can't contain anothersubmenu.Unavailable itemsSituations often occur where a certain function cannot be used. In these cases, thecorresponding items in the options menu must either be hidden, or there must be anerror message given when the user tries to access a function that can’t beaccomplished. Series 60 UI does not use dimming of menu items.This is a trade-off issue: removing unnecessary options makes the option lists shorter– an often desired result – but at the same time it changes the menu from situationto situation, preventing users from learning the function locations. It may even causefrustration if the users expect some function to be found in the menu, but it issometimes not there.In case the user has no reason to search for a certain function in the givensituation, it should be hidden. As an extreme example, the Delete option is notneeded when there are no items to be deleted.If the user searches for a function, even though it cannot be used in the currentsituation, it is often better to display the option and give an appropriate messageif the user tries to access that function.Other option menusSome option menus are accessed in other ways than by using the Options softkey.The usage of these menus is similar to the usual options menu. Examples of othersuch menus are:OK options menu The Select key opens this option menu when there’sno single intuitive function (like opening the item infocus) for it. The OK options menu only listsfunctions that:- affect the item in focus only- could be regarded as potentially intuitive- are competing for the topmost place of the menu.Other functions can be accessed through theOptions softkey. The number of items in the OKoptions list is usually two or three, it should neverbe more than four. As an example, in a messageeditor the functions in OK options could be Sendand Add recipient.52