In this paper we discuss some basic methodological considerations of the activities undertaken in the ACL-SIGSEM Working Group on the Representation of Multimodal Semantic Information. This independent expert group was founded on the instigation of the Interna- tional Organization for Standardisation ISO for investigating the possibilities to develop well-founded guidelines for the representation and annotation of semantic information in interactive multimodal contexts, with the aim to support the interoperability and reuse of multimodal and language resources.