with:1:0-NULL:2:1-fork:3:1 ate:1:0-the:2:3-meat:3:1 ate:1:0-with:2:1-fork:3:2 with:1:0-a:2:3-fork:3:1 NULL:1:2-He:2:3-ate:3:0 He:1:3-NULL:2:1-ate:3:0 ate:1:0-meat:2:1-NULL:3:2 ate:1:0-NULL:2:3-with:3:1 with:1:0-fork:2:1-NULL:3:2 NULL:1:2-a:2:3-fork:3:0 a:1:3-NULL:2:1-fork:3:0 ate:1:0-NULL:2:3-.:3:1 ate:1:0-.:2:1-NULL:3:2 (b) NULL:1:2-the:2:3-meat:3:0 the:1:3-NULL:2:1-meat:3:0  To provide bilingual subtree constraints, we need to find the characteristics of subtree mapping for the two given languages.
subtree mapping is not easy.