Additional information:

• A parameter is an element in its own right. It cannot therefore have the same name as an element of the same document. Case sensitive. An "a" parameter and an "A" parameter are differentiated, therefore are usable in the same document.

• The parameter name may contain spaces. If the parameter has a negative value, its name must be between ' '. For example, if the side's value should be the negative A B parameter, put -'A B' as the side's value.