[Libreoffice] Question about IAccessibility2

Hi all,

I have started to implement the attribute "stroke-linecap". I come 
across "IAccessibility2" in files
/core/cui/source/tabpages/tabline.hrc
/core/cui/source/tabpages/tabline.src
There are some string resources defined like
#define STR_END_LENGTH      41
Some are commented out in lines 125 to 134 in tabline.hrc. Such string 
resources are used in method SetAccessibleName in
/core/cui/source/tabpages/tpline.cxx

I see them for some controls but not for all, especially not for 
maLBEdgeStyle.

(1) What they are used for?
(2) Why they are set for some controls but not for all?
(3) Do I have to define such a string for my new linecap style list box?

Kind regards
Regina