Reliability and Availability Definitions
1. Reliability: probability a system or a capability of a system functions without failure for a specified time or number of natural units in a specified environment
2. Availability: the probability that a system or a capability of a system is functional at a given time in a specified environment
3 Natural unit: unit other than time related to output of software-based product, such as pages of output, transactions, telephone calls, or jobs
4. Failure intensity (FI): failures per natural or time unit