How linguistic constraints on movement conspireto yield languagesanalyzable with a restricted form of LIGs

Within a GB{like framework movement out of an object seems to be a valid concept for the description of natural languages whereas movement out of subjects and adjuncts is almost impossible. In a framework in which the notion object is determined conng-urationally, this condition on movement restricts the class of licensed structures. We will argue that this condition restricts as well the class of languages that can be generated. In order to study formal properties we transfer this condition to linear indexed grammars and deene two new formalisms: right linear indexed grammars and extended right linear indexed grammar. The classes of languages generated are proper subclasses of the class of linear indexed languages. In fact, we show that right linear indexed grammars are weakly equivalent to context free grammars, despite of the possibility to have in a derivation for each nonterminal an associated index stack (of unbounded depth). 1 Motivation Within a GB{like framework movement out of an object seems to be a valid concept for the description of natural languages whereas movement out of subjects, adjuncts and indirect objects is almost impossible (see e.g. M uller This paper has been worked out within the Innovationskolleg`Formale Modelle kog-nitiver Komplexitt at' (INK 12) funded by the Deutsche Forschungsgemeinschaft (DFG). Especially, we want to thank Peter Staudacher for constructive discussions and many helpfull comments.