let S be 1-sorted ; for R being NetStr over S holds NetStr(# the carrier of R, the InternalRel of R, the mapping of R #) is SubNetStr of R
let N be NetStr over S; NetStr(# the carrier of N, the InternalRel of N, the mapping of N #) is SubNetStr of N
( NetStr(# the carrier of N, the InternalRel of N, the mapping of N #) is SubRelStr of N & the mapping of NetStr(# the carrier of N, the InternalRel of N, the mapping of N #) = the mapping of N | the carrier of NetStr(# the carrier of N, the InternalRel of N, the mapping of N #) )
by YELLOW_0:def 13;
hence
NetStr(# the carrier of N, the InternalRel of N, the mapping of N #) is SubNetStr of N
by Def6; verum