Typically, the TLTAG Selection process selects all elementary TLTAG trees from the TLCS-TLTAG Resource in which their TLCSs precisely agree with the TLCS input.
in this case, the Lexical Replacement pattern forces the process to specifically choose the trees not just only whose TLCSs are identical to the TLCS input but also whose syntactic structures are the same as that of the TLCS input tree.