Displays neos

Database access dif f icult

People find it hard to get the right information from a database. And using search trees or keywords both present problems. These are the findings of a joint study carried out at the Institute for Perception Research and Philips Research Laboratories in the Nether- lands.

The study investigated the barriers that have to be overcome by untrained people if they have to search for a particular TV programme in a database contain- ing the TV programmes for a week. A comparison of the use of a search tree with the use of keywords shows that keywords lead to the desired goal slightly faster, but that half the people involved in the experiments nevertheless preferred to use a search tree. This means that databases should preferably be accessible by both search methods; and these should be made as simple as possible.

To investigate the difficulties that can arise in a man-machine dialogue, untrained subjects were asked to search materials in the database selected to have sufficient association with every- day experience to provide motivation for the subjects. The data was made accessible to the subjects in two ways - through a search tree and through keywords. However, only some of the programmes could be directly retrieved with keywords. For the remaining programmes a search tree still had to be used after an initial keyword.

The study involved both male and female subjects, aged from 21 to 58, with occupations varying from research worker to waitress. The subjects were asked to search for ten different TV programmes each time, five using the search tree method and five using the keyword method. A previous test had already shown that each series of five assignments contained some items that were easy to find and some that were

difficult. All instructions were given using the display screen.

In the most favourable case, the search based on the search tree method required 19 pages (each a full screen display). But about half of the subjects had to call up more than twice that number. With the keyword method fewer pages were necessary to reach the objective - a minimum of 15. Only a few people now took more than twice as many page.~ and that was mainly because of their unfortunate choice of keywords. Another barrier in searching with keywords was that the words had to be typed in and this took extra time. In spite of this, pro- gress was faster when searching with keywords. Nevertheless, half of the subjects preferred the search tree.

Subjects went wrong in a number of ways. Many could not remember the choices they had already made, so that pointless repetitions occurred if a programme could not be found straight away. It was also found that the subjects often overlooked parts of the text on a page. A good page layout is therefore very important. Some were diverted from their original course by apparently interesting sub- jects that they saw on the screen. Others stopped searching through a particular group before they had looked at all its components.

The study concluded that searching for data, even from a simple database, is far from easy. Search methods must thus be made as simple as possible. Particular attention should be paid to the arrangement of the information and the page layout of the display screen. Software should be designed in such a way that the base can be accessed both by the search tree and by keywords.

Philips, PO Box 523, 5600AM Eind- hoven, The Netherlands

Test con t rac t f o r f l a t C R T

Automatic testing equipment for Sinclair's Microvision TV (see Displays 2 (1981) 317) is being designed and developed by Aim Cambridge in a con- tract awarded by Timex. Timex is due to start manufacturing the Sinclair- designed fiat CRT later this year.

The equipment tests three tubas at a time. Six electrical and seven optical tests are performed in about ten seconds. Each of the three test stations is controlled by a microprocessor, with a fourth microprocessor to control overall operation of the mechanical handling system and test stations and to communicate with the factory's database.

Among the tests performed are checRs on spot brightness, tube geometry and deflection sensitivity in two directions. Focus quality is ensured by examining the spot area and optimizing the voltage on one electrode. A slow raster scan of the screen is used to check for major defects in the phosphor.

Aim Cambridge Ltd, Burrel Road, Industrial Estate, St Ives, Cambs PE 17 4LE, UK

Quality control for the Sinclair Microvision flat screen tube

DISPLAYS. JULY 1982 161