ILOG OPL Development Studio Language Reference Manual

OPL formulationTypically, the problem structure will indicate if an interval can be optional or not, and thekeyword optional is used (or not) in the definition of the interval variable. In the case wherethe optionality depends on input data, you can specify a boolean parameter to the optionalityfield: optional(true) being equivalent to optional and optional(false) beingequivalent to the omission of optional.A window [StartMin,EndMax] can be specified to restrict the position of the interval variable.By default, an interval variable will start after 0 and end before maxint/2. The fixed size orthe size range for the interval is specified with the size keyword. Note that these bounds aretaken into account only when the interval variable is present in the final schedule, that is, theyallow specifying conditional bounds on the interval variable would the interval be present inthe final schedule. For absent intervals, they are just ignored.dvar interval a [optional[(IsOptional)]][in StartMin..EndMax][size SZ | in SZMin .. SZMax][intensity F]Where:int IsOptional, StartMin, EndMax, SZ, SZMin, SZMax;stepFunction F;-maxint/2 + 1