sli components are sli.io, sli.xref
sli specification is in sli.ads
sli body          is in sli.adb
sli.io specification is in sli-io.ads
sli.io body          is in sli-io.adb
sli.xref specification is in sli-xref.ads
sli.xref body          is in sli-xref.shb
