Abstract. A formal architecture for Construction Grammar (CG) is sketched. Modeling domain objects (constructs) are constituent structures with feature structures at the nodes, aka Feature Structure Trees (FTs). Constructions are partial descriptions of FTs, expressed as sets of constituent structure equations and path equations. Unification of constructions is defined. A construct c is licensed by a grammar G iff G contains a set of constructions whose unification fully describes c. Key words: constraint-based, constructions, construction grammar, grammatical constructions