Semantic role annotation of instrument subjects

Semantic role annotation has become widely used in NLP and lexical resource implementation. Even if attempts of standardization are being developed, discordance points are still present. In this paper we consider a problematic semantic role, the Instrument role, which presents differences in definition and causes problems of attribution. Particularly, it is not clear whether to assign this role to inanimate entities occurring as subjects or not. This problem is especially relevant 1- in reason of its treatment in practical annotation and semantic role labeling, 2- because it affects the whole definition of semantic roles. We propose arguments to sustain that inanimate nouns denoting instruments in subject positions are not instantiation of Instrument role, but are Cause, Agent or Theme. Ambiguities in the annotation of these cases are due to confusion between semantic roles and ontological types.