Displays neuJs

Keyboards add to d i scomfo r t

Reflections from the keyboard of a visual display unit may contribute to the level of discomfort glare experi- enced using such equipment, accord- ing to a report from the UK Building Research Establishment. This is in addition to the more widely reported problems of reflections from the VDU screen itself.

The report gives recommendations for avoiding glare in both these cases. Reflections in the near horizontal key- board are reduced if the keys have a matt finish and may be easily cleaned so that the greasy specular f i lm which builds up from contact with the keys can be removed.

Both problems may be combatted by modifying the surrounding lighting rather than the equipment itself. The bright luminaires can be eliminated or replaced by indirect lighting or lower- luminance luminaires. A narrow down- ward light distribution with a maxi- mum cut-off angle of 55 ° from the downward vertical is recommended.

Alternatively, the VDU may be positioned to avoid these reflections. But, the report points out, this is often diff icult because many VDU screens are curved and a wide range of viewing angles can be used. Best results should be obtained by placing the VDU such that the operator's line of sight is parallel to the luminaires and to the windows.

The remainder of the report, entitled 'Office lighting for good visual task conditions', explains the use of the contrast rendering factor (CRF) in quantifying the effect of reflections, and suggests suitable CRF levels. Design ideas for maximizing the CRF are included.

Building Research Station, Garston, Watford, Hefts WD2 75R, UK

Glare may occur by reflection from the key- board and by reflection from the screen from luminaires spread over a wide angle

Proof reading

Spelling verification and hyphenation for I BM's document composition facil ity and spelling verification for its Displaywriter stand-alone word pro- cessor are some of the functions included in IBM's Proof - a n acronym for 'principal's on-line office facility'. Spelling correction is also offered for other IBM word processors and some experimental functions' are included.

A dictionary of 50 000 words forms the heart of Proof. For spelling verifi- cation, every word in a document is checked against this dictionary. Words not found there are flagged on the screen of the visual display unit more brightly than other words or in a different colour. Misspelled words can then be corrected. Other words, such as names, acronym~ or simply ones not included in the dictionary, are also flagged but can be ignored. (These unwanted words flagged were later found to constitute basic abstracts of documents.)

By representing each letter of the alpha- bet as a vector, words can be given identities. Each letter is characterized by a magnitude and direction, the values

of which may be added up for each letter of a word to give it a pair of virtually unique values. I t is these values - not the words themselves - that are stored in the dictionary. This makes i t compact enough for imple- mentation in the relatively small Displaywriter.

The verifier was extended for use with eight European languages, including British English. An effort to modify it for people writing English as a foreign language led to the idea of an 'on-line thesaurus'. The system was then developed to produce synonyms on request, and so far 11 000 have been cross-referenced. Another step was to develop an algorithm to deal with homonyms. This flags each member occurring of a number of defined 'confusable sets' and presents the remainder of the set with brief definitions.

Spelling correction follows on from verification. The commonest spelling mistakes were collected, and algo- rithms designed to take into account misspellings due to mishearing, typo- graphical slips and other errors. By assigning similar values to letters often confused, the dictionary can be made to come up with words with similar code representations from which the user picks the correct spelling.

IBM workers are now concerned mainly with processing at the text level. Their experimental system, Epistle (evaluation, preparation and interpretation system for text and language entities), is designed to incor- porate a dictionary including, for each entry, parts of speech, inflected forms, allowed affixes and possibly a pronun- ciation guide. A syntax analyser, now in an experimental form, wil l be able to correct grammar.

IBM Corporation, Thomas J. Watson Research Center, PO Box 218, Yorktown Heights, NY 10598, USA

DISPLAYS. APRIL 1982 113