Module name: dss_aux
Author: Ian Stewart (University of Leicester, ims@star.le.ac.uk)
The routines are designed to act as an additional layer over the dsslib library. They implement many useful short cuts.
Full information about the Data Sub Space (DSS) should of course be sought in the dsslib task documentation. However a few explanatory words here would not be out of place.
The function of the DSS is to store information about the criteria used to select events. Thus an XMM event list may contain a DSS if it has been filtered in some way; XMM products such as light curves or spectra, which have been created from event lists, nearly always filtered, may also contain them.
The formal structure of a DSS comprises a list of components, each of which may contain a list of filters. Suuposedly the selection should be reconstructed by ANDing all the filters for each component then ORing all the components, but many filter types (eg GTIs) imply a logical OR internal to the filter.
The DSS is implemented in terms of keywords and extensions, but it is not intended that the user should need to know how the DSS is encoded in these things: the dsslib library supplies subroutines to permit basic access to the DSS details without this knowledge.
