The string data type is used exactly how it is encoded in the file. The interpretation of the value is controlled by the attribute specification. The attribute specification includes case sensitivity, enumerated values, and default value. If the attribute indicates that the value is case insensitive, the string is converted to lower case before any processing. If a value is not supplied, then the default value is used. If the attribute specifies that the value is enumerated and the value is not one of the allowed values, then the default value is used.
The value must follow all HTML rules for encoding attribute values and must be enclosed in either single or double quotation marks (HTML requirement).