A method for determining differential availability, the method including identifying a current context of a first entity, and determining a current availability value of the first entity with respect to a second entity in accordance with an availability function, where the availability function is adaptive in accordance with an adaptation process to at least one past actual availability value of the fist entity with respect to the second entity in a previous context at least partially related to the current context, and where the availability function is operative to determine the current availability value as a function of the current context.