Data reliability can refer to the origin of the data on the one hand. So the source of the data is reliable and trustworthy. And on the other hand, reliability can also refer to intrinsic quality characteristics such as completeness, accuracy and freedom from redundancy.
Since reliability is a summary of the previous quality metrics, this value can only be determined indirectly and should be clearly defined by the researcher beforehand.
For example, reliability can be a combination of accuracy, completeness and consistensy. A value can then be a combination of these metrics with different weights. Depending on the needs of the researcher.