Errors, faults and failures

Abstract

Aim. To harmonize the definitions of errors, faults, failures in the Russian and English languages. The Object of the paper is one of the most important subject matters of the dependability theory and functional safety. The Subject of the paper is the concepts and definitions of failures, errors, faults.Results of the research: analysis of the definitions of the concepts describing the dependability and functional safety of items in the Russian and international standards, such as GOST 27.002-2015, GOST R/IEC 61508-2012, IEC 60050, DIN 40041, as well as in publications by a number of authors. The analysis shows that failure is always associated with the loss of function, i.e., the ability to perform as required by all standards. It should be noted that wrong user expectation does qualify as failure. A failure should be distinguished from unintended functions. A fault is defined as a system’s inability to perform the required operation to the full extent that, under certain conditions, may escalate into a failure. An error as a discrepancy between a calculated, observed or measured value or condition and a true, specified or theoretically correct value or condition is a deviation that is present and, under certain conditions, would probably turn into a failure. A typical example is non-critical software errors. The so-called systematic failures are actually errors that can turn into critical errors (failures). Let us note that the definitions in the IEC 60050 international electrotechnical vocabulary can be used, as they show general agreement, which is not surprising for an international standard.