The quality of collected data is the crucial parameter which determines the quality of outputs and the overall success of the project. Validation of data entered into the system helps to ensure that these data are perfect, formally correct, comply with the required characteristics and thus can be used for further processing and/or analysis.
In principle, data validation can be performed in two sides. The first possibility is the internet browser (client side), where the validation is performed via client scripts. In the case of client-side validation, data are checked before being saved (i.e., sent to the server). In other words, the browser does not allow sending data which do not meet the input requirements. The main advantage of client-side validation is the rapidity, as it is not necessary to send the data to the server to validate it. The disadvantage of this approach is the fact that the internet browser is fully controlled by the user, who can forbid client scripts, for example, or differently get around the validation.
For this reason, it is sometimes appropriate (or even necessary) to combine the client-side validation with the server-side validation. In this case, the data are sent to the server, where the check is performed. If the data do not comply with the requirements, the user is informed about the detected problem. The main advantage of this approach is the fact that the user cannot circumvent it in any way. An obvious disadvantage is slowing down the whole process (data must be sent to the server in order to be checked).
Basic types of validation include:
Furthermore, data validation enables the usage of items to be calculated or filled in automatically, based on other items. Automatically-filled items contribute to a higher quality of data, as the number of manually-filled items is decreased, where the user might possibly enter wrong data (e.g. by making a mistake in calculation).