Data intelligibility means that the information a computer retrieves is comprehensible to another computer system or a human viewer. Intelligibility may occur at three levels. At its most simple level, intelligibility occurs when two computer systems either use or understand the same digital representation of the information, and this representation is translated into a form that humans recognize and understand. A prime example of an understandable form is an American Standard Code for Information Interchange (ASCII) text file.
The second level occurs when two computer systems can use or understand the same representation of the information (e.g., ASCII), but when the representation is presented to users, it does not carry sufficient information (e.g., it is not self-referential) for a human to comprehend. Usually, this problem is associated with both coded and numerical data, and the intelligibility of such information can only be assured through documentation defining the values represented by the numbers and codes.
The third level occurs when two different software applications, functioning in different computing environments, can process the same digital data and achieve identical results. One example of this is a text document embedded in one word-processing system that can be processed by a totally different word-processing system with no loss of information or page formatting details such as type fonts and line spacing. This lack of intelligibility becomes particularly evident when a proprietary encryption scheme is encountered or when digital images are compressed based on a proprietary technique.