What are sources of best practice?

Customers, suppliers, and advisors are stakeholders and parties in service relationships, not categorized as sources of best practice in ITIL terminology.

ITIL formally identifies industry practices, academic research, and training and education as recognized sources of best practice, alongside standards bodies and internal organizational experience - these represent validated, externally-derived knowledge that is systematically incorporated into IT service management guidance such as the ITIL framework itself.

Substitutes, regulators, and customers are drawn from competitive analysis frameworks such as Porter's Five Forces and do not map to ITIL-defined sources of best practice.

Competition, compliance, and commitments describe external business drivers or obligations, not the knowledge sources from which best practices are derived and validated.