Data
Anything that a computer system can store and process is considered to be data. In practice this means that data could be.
| fact | such as a person's surname or the price of a good |
| event | such as a change of address or the arrival of new stock |
| transaction | such as a sale, order or reservation. |
Data will not normally be isolated but will occur as part of a group. It will have structure which we call a record relating to an activity or entity and data capture will usually be concerned to collecting a succession of similar data groupings within a given time period.
In a business system, data will arise naturally as transactions occur. It may also arise as a by product of another operation such as when a weekly stock check program generates data about sales of particular categories of good.
There are a number of methods used to collect data, the particular method depending on the nature and volume of the information to be collected.
| Data Capture | Data is captured automatically at the point of origin or source document - such as a bar code system in a supermarket |
| Data Preparation | Data is manually copied (transcribed) from the source document to a computer readable format. This is done off-line. Data preparation introduces the real possibility of transcription errors and this stage would normally be followed by verification. |
| DDE | Direct Data Entry. Data is keyed in as the transaction takes with details being checked on screen. An example would be when a holiday booking is made. |
If there is a large volume of data to be collected and the structure is similar then data capture or data preparation methods will be used. Automatic methods are increasingly being used to reduce the chance of transcription errors and also to reduce running costs since, although data capture methods may involve a high initial outlay, the running costs are less than employing a large number of data preparation clerks.
It is also possible to use elements of more than one method, particularly where turnaround documents are involved. Many companies now identify invoice details with a bar code printed on the invoice. These details are read in by a hand scanner when the customer returns the invoice with his or her payment. The amount paid can be keyed in using DDE.
Specialist methods are also used to suit particular applications. For example gas and electric meter readers may have hand-held data loggers to record meter readings. The readings are stored in the device for downloading at the end of the day, thus eliminating the data preparation stage. Similar systems are used by traffic wardens and ticket inspectors on buses in some cities. In some situations the data could be transmitted by microwave or radio link to a central computer system as it is collected.
Errors in data will lead to errors in processing and output. These may have far reaching consequences and be difficult to spot so various controls are applied to data collection and input in an attempt to identify and correct erroneous data.
Verification checks for transcription errors introduced when data is copied from one format to another. This is particularly used when manual data preparation takes place but it is also used whenever data is copied from one medium to another.
Source documents can be manually checked before being submitted for data preparation or OCR input. This method is particularly appropriate if some of the data on the source document is to be coded for input.
Validation checks can be made when the data is input and during processing.
On line DDE systems can display data on screen for checking before processing takes place. If a holiday is booked then entering the code number for the package would bring up details on the screen. These could be checked before confirming the data for processing or even printed off and given to the customer to check.
| A Level ICT 2nd Edition | P. M. Heathcote | Chpt 42, 43 |
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