EFFECTS OF LINGUISTIC SOPHISTICATION ON THE USABILITY OF A NATURAL-LANGUAGE INTERFACE

Casual users of database systems are not skilled in structured query languages. Natural language interfaces (NLIs) could provide them with the flexibility and ease of use that they require. The paper challenges the dictum that the usability of an NLI is enhanced when its linguistic capabilities are extended. It is argued that effective natural language communication needs a naturalistic sublanguage of English, reduced in complexity, but nevertheless providing the flexibility of natural language input. Two investigations are described, both of which involved real users performing real information retrieval tasks. The first gives an insight into the detailed characteristics of such a sublanguage, providing a comparison with earlier research. The second compares the effect of intersentential linking devices like ellipsis, on the usability of an NLI, with that of simple, extralinguistic editing facilities. The results show-that enhanced linguistic capabilities can indeed improve usability under certain circumstances, but that extralinguistic enhancements can be just as effective. The results also show that usability can actually degrade as both the linguistic and the extralinguistic capabilities of an interface are improved.