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Help: blue = parse found inside. Abbreviations: WS: Workspace; SO: Syntactic Object; IA/EA: Internal/External Argument; INT/EXT: interface SO post-Merge/FormCopy; Initial WS: heads that may project after LEX word lookup. ...
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Words: a train arrived
Initial WS 1: arriveθ varrive:past INFLv traina
WS 1: {arriveθ, traina} varrive:past INFLv
WS 2: {varrive:past, {arriveθ, traina}} INFLv
WS 3: {traina, {INFLv, {varrive:past, {arriveθ, traina}}}} 
Final WS: {C, {traina, {INFLv, {varrive:past, {arriveθ, traina}}}}} 
INT/EXT: {C, {traina, {INFLv, {varrive:past, {arriveθ, train:aa}}}}}
Initial Spellout: a train 3sg past arrive
Spellout: a train arrived
Parse found: a train arrived
Initial WS 2: arriveθ varrive:past INFLv trainθ vtrain:θ:pres INFLv
Error: Word actions [addFType(det,a,type(θRnoun))] failed to apply!
Initial WS 3: arriveθ varrive:past INFLv trainθ vtrain:θ INFLv
Error: Word actions [addFType(det,a,type(θRnoun))] failed to apply!