Throughout the preceding sections we have presented the main (morpho-)syn- tactic characteristics of DGS. In our sketch, we have focused on the expression of grammatical relations at the sentential level, advancing also the relevance of considering the level beyond syntax proper for a more comprehensive understanding of the linguistic devices used in languages using the visuo-gestural modality of expression. As will become apparent in the following discussion, phenomena that involve the syntax-discourse interface are also indicative of how mastery of the language involves a skilful integration of knowledge from distinct levels of linguistic analysis.
Subject drop and discourse topic drop
DGS, like other sign languages, has been found to instantiate properties of sentence-oriented languages and discourse-oriented languages (Hanel 2005: 111). This is reflected in DGS allowing for two types of null arguments, that is, argu- 
ments that may remain phonetically empty. We learned before that arguments in constructions with agreement verbs may remain phonetically unexpressed (or “dropped”, hence the notions of subject drop or object drop) because they are identified through agreement markings. This type of null argument licensing is encountered in sentence-oriented languages. By contrast, the possibility to drop arguments in constructions with plain verbs is bound to discourse conditions. Example (48) shows that the subject may remain phonetically empty because it is identical with the subject of the preceding clause (Sauer et al. 1997: 77, our transl.).
-  Previous analyses (see Lillo-Martin 2002: 247 for further details) distinguished (a) first person(marked by the location of the signer), (b) second person (marked by the location of the addressee), and (c) third person marked by using other spatial locations. However, the loci for third andsecond person are indistinguishable, a distinction being possible only through the role played bythe referent in a particular discourse context (Lillo-Martin 2002: 247, pace Meier 1990).
-  Within a generative model of grammar, indices in these constructions represent variables thatare bound by an operator in the topic position, an option that is available in discourse orientedlanguages (Sauer et al. (1997) based on Lillo-Martin (1991), cf. also Hanel 2005: 111).