The concept of data is usually distinguished from the concepts of information and knowledge. If a datum is a fact about the real world, the meaning that we derive from it is information.
EX. WM-2:
Some data can have objective meanings. One objective meaning of -10° C is that it is below the freezing point of water.
Data are often given subjective meanings. A subjective meaning of -10° C for the author is usually the following: “it’s cold!” Given that it is subjective, this temperature reading could be interpreted differently by other people. It may be considered “warm” by people who live in colder climes.
Meaning may be conveyed in the data format conventions developed for a given data type.
EX. MVR-2:
Authorities such as the police and tax officials can derive meaning from our motor vehicle identifier depending on how the codes are assigned. Suppose the fields of characters and numbers are each given a role. They could each be designated to represent something specific beyond providing a unique identifier for a vehicle. The first field, %c%c%c, could be used to represent cities or areas of the province. The second field, %d%d%d, could be used to provide a unique number for a vehicle within an area. Suppose all vehicles within the town of Fredericton, New Brunswick are assigned values in the first field of their licenses starting with the characters ‘FR.’ Examples would be:
FRA 102FRA 037FRZ 321
Thus, people who know these roles would be able to derive some knowledge about the vehicle’s place of registration by looking at the first field.
Sometimes it is necessary to distinguish one meaning from another. In other words, we may wish to represent such distinctions in the data themselves. This data modeling problem helps give us a partial understanding of what knowledge is.
EX. WM-3:
If the author thinks that -10° C is cold, what about -9° C or -11° C? We can measure the numeric differences between these quantities. In a data management system, however, it may be necessary to define what “cold” means in a given context. In this case, we might define the following rule in our data management system to establish the meaning of cold.
IF temperature <= 0 ° C THEN cold = true;
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