This chapter describes a model and an underlying theoretical framework for hybrid planning. Modern planning domain description languages are based on sentential representations. Sentential formalisms produce problem encodings that often lead the system to carry out large amounts of superfluous operations, causing a loss in performance. This chapter illustrates how techniques from the area of knowledge representation and reasoning (in particular, analogical representations) can be adopted to develop more efficient domain description languages. Although often more efficient, analogical representations are generally less expressive than sentential ones. A framework for planning with hybrid representations is thus proposed, in which sentential and analogical descriptions can be integrated and used interchangeably, thereby overcoming the limitations and exploiting the advantages of both paradigms.