Karen Spärck Jones
John Irving Tait · Computational Linguistics · 2007
Karen Spärck Jones died peacefully on 4 April 2007 after a number of months battling cancer.Karen was President of the Association for Computation Linguistics in 1994 during a difficult period, and saw through a transitional phase in which a solid basis for the long-term health of the association was established.Karen was an exceptional individual who made very substantial contributions in two separate fields, computational linguistics (CL) and information retrieval (IR), as well as in computing and artificial intelligence more broadly.In IR, her greatest contribution was probably her invention (1972) of the concept of inverse document frequency (IDF), in which the importance of terms is weighted according to the proportion of documents in the corpus in which they occur; the intuition being that terms which occur in many documents are poor index terms.This is the partial basis of all weighting schemes adopted by widely used Internet search engines, and will undoubtedly be a lasting contribution to the field.Her primary inspiration and interest was always language, especially language in practical use.Her long involvement with IR arose (as someone who subsisted for an inordinately long time on soft money) by the need to find a new line of research in the aftermath of the ALPAC Report and the subsequent difficulties in getting machine translation work funded.However, she was always well qualified to work in IR, a topic addressed in her very early publications (see, for example, Masterman, Needham, and Spärck Jones 1958), although in a rather different context to her later work.Given this focus on language it is therefore perhaps odd that her main contributions to CL or natural language processing are harder to pin down.They include contributions to summarization, natural language interfaces to structured databases, dialogue, semantics, and more.In the long term perhaps her greatest contribution will come to be seen to be her Ph.D. thesis (1964), which was far ahead of its time.It brought together statistical or machine learning approaches with the use of an existing resource (Roget's Thesaurus-punched onto cards!) and still can be read with profit today (see Wilks and Tait 2005).It can be viewed as the forerunner of a whole range of more recent attempts to derive semantic information on an empirical basis.It is perhaps as an empiricist that Karen will be best remembered.Her long associations with the US TREC initiatives and the more recent DUC summary evaluations are well known, as is her earlier association with DARPA TIDES, but her desire to work on well-founded experimental bases runs through from her earliest days, initially through involvement with Cyril Cleverdon and the Cranfield project, and then later in the work reported, for example, in Spärck Jones and van Rijsbergen (1976) and Spärck Jones and