Encoding Data

Data is often coded before storage. For example a series of two letter codes could be used to store the colour of a car. The advantages of coding are:

• Less storage space is required
• Comparisons are shorter and can therefore be made more quickly - thus speeding up searches
• A limited number of codes ensures that when a search condition is specified it will be in the same terms as the data is stored.

Encoding data also has some disadvantages:

• The precision of the data may be coarsened. For example light blue may have to be coded as blue. This coarsening may not be apparent to the user if the code is turned back into a colour name on output.
• The user needs a list of valid codes and their meanings to use the system.

In some situations there may be no absolute agreement on the value of a data item. This is the case when a value judgement has to be coded for computer input. A value judgement is something that is a matter of opinion rather than of fact. An example might be data collected on a dating agency form - I am handsome / good looking / average / ugly. The problem with a value-judgement is that there is no single correct value. The value depends on someone's opinion. Coding of value judgements will inevitably lead to coarsening of the data since there will be a wide range of opinions that could be held and only a limited number of codes available.

© LEV