HUMAN-COMPUTER INTERACTION
SECOND EDITION
HUMAN-COMPUTER INTERACTION
SECOND EDITION
Handwriting is a common and familiar activity, and is therefore attractive as a method of text entry. If we were able to write as we would when we use paper, but with the computer taking this form of input and converting it to text, we can see that it is an intuitive and simple way of interacting with the computer. However, there are a number of disadvantages with handwriting recognition. Current technology is still fairly inaccurate and so makes a significant number of mistakes in recognizing letters, but has improved rapidly. Moreover, individual differences in handwriting are enormous, and make the recognition process even more difficult. The most significant information in handwriting is not in the letter shape itself but in the stroke information -- the way in which the letter is drawn. This means that devices which support handwriting recognition must capture the stroke information, not just the final character shape. This means that on-line recognition is far easier than reading handwritten text on paper. Further complications arise because letters within words are shaped and often drawn very differently depending on the actual word; the context can help determine the letter's identity, but often is unable to provide enough information. Handwriting recognition is covered in more detail later in the book, in Chapter 15. More serious in many ways is the limitation on speed; it is difficult to write at more than 25 words a minute, which is no more than half the speed of a decent typist.
Some organizer designs have dispensed with a keyboard completely. With such systems one must consider all sorts of other ways to interact with the system that are not character based. For example, we may decide to use drawings to tell the system what to do rather than commands using gesture recognition, for example drawing a line through a word in order to delete it. The important point is that a different input device that was initially considered simply as an alternative to the keyboard opens up a whole host of alternative interface designs and different possibilities for interaction. Pen-based systems that use handwriting recognition often use a special pen-based operating system, which attempts to tackle some of the problems of using a pen-based approach to what is otherwise a standard keyboard and mouse-oriented system, in much the same way as we suggested above, although there are also pen-based versions of standard operating systems.
Speech recognition is a promising area of text entry, but it has been promising for a number of years without actually delivering usable systems! It is forecast that the market for a successful system runs into billions of pounds and therefore a lot of development work is being put into this area. Indeed, practical systems are beginning to be delivered commercially so a major growth in this area may occur in coming years. There is a natural enthusiasm for being able to talk to the machine and have it respond to commands, since this form of interaction is one with which we are very familiar. Successful recognition rates of over 97% have been reported, but since this represents a letter in error in approximately every 30, or one spelling mistake every six or so words, this is stoll unacceptible (sic)! Note also that this performance is usually quoted only for a restricted vocabulary of command words. Trying to extend such systems to the level of understanding natural language, with its inherent vagueness, imprecision and pauses, opens up many more problems that have not been satisfactorily solved even for keyboard-entered natural language. Moreover, since every person speaks differently, the system has to be trained and tuned to each new speaker, or its performance decreases. Strong accents, a cold or emotion can also cause recognition problems, as can background noise. This leads us on to the question of practicality within an office environment: not only may the background level of noise cause errors, but if everyone in an open-plan office were to talk to their machine, the level of noise would dramatically increase, with associated difficulties. Confidentiality would also be harder to maintain.
A common requirement of word processors and desktop publishing software is that what you see is what you get (see also Chapters 4 and 9), which is often called by its acronym WYSIWYG (pronounced whizz-ee-wig). This means that the appearance of the document on the screen should be the same as its eventual appearance on the printed page. In so far as this means that, for example, centred text is displayed centred on the screen, this is reasonable. However, this should not cloud the fact that screen and paper are very different media.
Optical character recognition (OCR) is the process whereby the computer can 'read' the characters on the page. It is only comparatively recently that print could be reliably read, since the wide variety of typefaces and print sizes makes this more difficult than one would imagine -- it is not simply a matter of matching a character shape to the image on the page. In fact, OCR is rather a misnomer nowadays as, although the document is optically scanned, the OCR software itself operates on the bitmap image. Current software can recognize 'unseen' fonts and can even produce output in word-processing formats preserving super- and subscripts, centring, italics and so on.
Workers at Xerox Palo Alto Research Center (also known as Xerox PARC) capitalized on this by using paper as a medium of interaction with computer systems [125]. A special identifying mark is printed onto forms and similar output. The printed forms may have check boxes or areas for writing numbers or (in block capitals!) words. The form can then be scanned back in. The system reads the identifying mark and therefore knows what sort of paper form it is dealing with. It doesn't have to use OCR of the printed text of the form as it printed it, but can detect the check boxes that have been
(a) portable word processor
(a) portable word processor
The determining factors are size, weight and battery power. However, remember the purpose: this is a word processor not an address book or even a data entry device.
(iii) Real keyboard -- you can't word process without a reasonable keyboard and stylus handwriting recognition is not good enough.
processed in 0.003 seconds
|
| |
|
HCI Book 3rd Edition || old HCI 2e home page || search
|
|
| feedback to feedback@hcibook.com | hosted by hiraeth mixed media |
|
| |