Other attributes such as StcsCoords and StcsProps can be used to specify other Objects to be returned
by AST_READ. If more than one of these attributes is set non-zero, then the actual Object returned by
AST_READ will be a KeyMap, containing the requested Objects. In this case, the Region representing
the STC CoordinateArea will be stored in the returned KeyMap using the key
" . If StcsArea is
the only attribute to be set non-zero, then the Object returned by AST_READ will be the
CoordinateArea Region itself.
The class of Region used to represent the CoordinateArea for each STC-S sub-phrase is determined by
the first word in the sub-phrase (the
" sub-phrase identifier
" ). The individual sub-phrase Regions are
combined into a single Prism, which is then simplified using AST_SIMPLIFY to form the returned
Sub-phrases that represent a single value ( that is, have identifiers
" ) are considered to be be part of the STC CoordinateArea component.
The TimeFrame used to represent a time STC-S sub-phrase will have its TimeOrigin attribute set to the sub-phrase start time. If no start time is specified by the sub-phrase, then the stop time will be used instead. If no stop time is specified by the sub-phrase, then the single time value specified in the sub-phrase will be used instead. Subsequently clearing the TimeOrigin attribute (or setting its value to zero) will cause the TimeFrame to reprsent absolute times.
The Epoch attribute for the returned Region is set in the same way as the TimeOrigin attribute (see above).