Business/IT alignment is a key management issue and has been largely investigated. Requirement engineering now deals with goal modeling and enterprise modeling; it addresses the "function integration" but doesn't explicitly addresses the "strategic fit". The assumption of this talk is that making explicit the business model can contribute to improving the business/IT alignment. The role of a formally defined business model is outlined. We propose a Business Model Ontology to formulate, understand, analyze and share a company's business model when designing information systems.