This special issue presents the state-of-the-art in implemented,
general-purpose
Natural Language Processing (NLP) systems that use nontrivial Knowledge
Representation
and Reasoning (KRR). These systems use full-scale implementations of
traditional KRR techniques as well as some newer knowledge-related processing
mechanisms that have been developed specifically to meet the needs of natural
language processing. The papers cover a wide range of natural language
inputs,
knowledge and formalisms, application domains and processing tasks, illustrating
the key role that knowledge representation plays in all types of NLP systems.