Architecture of the Select Options 
Select Options provide various options differing in complexity for defining selection criteria.
Select Options consist of a Web Dynpro component (WD_SELECT_OPTIONS_20), which is integrated using the Web Dynpro interface, of a handler class (CL_WDR_SELECT_OPTIONS_20), and an assistance class (CL_WD_SELOPT_UTIL_20).
Web Dynpro component WD_SELECT_OPTIONS_20 has an interface, multiple methods, events, and an interface view.
Handler class CL_WDR_SELECT_OPTIONS_20 has interface IF_WD_SELECT_OPTIONS_20.
Help class CL_WD_SELOPT_UTIL_20 has static methods GET_OPERATOR_TEXT, GET_DETAILS_FOR_TYPE, GET_DEFAULT_OPERATOR, CONVERT_RANGES_INTO DATA, and CONVERT_DATA_INTO_RANGES.

Architecture of the Select Options
You can find an example in the system in component WDR_TEST_SEL_OPTIONS_20.
Select a test case on tab Single Test Cases. You can change the layout on tabs General Visibility, General Texts, and Global Settings. On tab Edit Attributes you can look at the definition of the attributes. To display the Select Options choose the Render button. With the functions now available you can try out the various methods of interface IF_WD_SELECT_OPTIONS_20.