a risk-based manner, optimizing effort and ensuring that computer system's fitness for purpose is demonstrated. the overall risk posed by a computer system is now generally considered to be a function of system complexity, patient/product impact, and pedigree (configurable-off-the-shelf or custom-written for a certain purpose). a lower risk system should merit a less in-depth specification/testing/validation approach. (e.g. the documentation surrounding a spreadsheet containing a simple but "gxp" critical calculation should not match that of a chromatography data system with 20 instruments) determination of a "gxp critical" requirement for a computer system is subjective, and the definition needs to be tailored to the organisation involved. however, in general a "gxp" requirement may be considered to be a requirement which leads to the development/configuration of a computer function which has a direct impact on patient safety, the pharmaceutical product being processed, or has been developed/configured to meet a regulatory requirement. in addition if a function has a direct impact on gxp data (security or integrity) it may be considered "gxp critical". product life cycle approach in validation validation process efforts must account for the complete product life cycle, including developmental procedures adapted for qualification of a drug product commencing with its research and development phase, rationale for adapting a best fit formula which represents the relationship between required outputs and specified inputs, and procedure for manufacturing. each step is required to be justified and monitored in order to provide a good quality food and drug product. the fda emphasizes the product life cycle approach in its evaluation of manufacturer regulatory compliance as well.