Few pairs of terms cause as many misunderstandings in projects between Germany and Switzerland. Whoever speaks of a Pflichtenheft means something different depending on the country.
The German distinction
Under DIN 69901 and common German usage, the client sets out its requirements in the Lastenheft: what the system must do and under which constraints. The contractor responds with the Pflichtenheft, describing how it will meet those requirements. Once approved, the Pflichtenheft becomes the binding basis for implementation.
Swiss usage
In Switzerland, especially in public tenders, the client’s requirements document is usually called the Pflichtenheft. It contains the starting point, requirements, constraints and often the suitability and award criteria. The supplier’s solution description is then part of the bid, as a concept or solution outline. Anyone working with German and Swiss partners should clarify at the outset which meaning applies.
What belongs in a good requirements document
Whatever its name: goals and starting point, system boundaries and interfaces, functional and non-functional requirements with priority, acceptance criteria, constraints such as data protection, security and operations, a glossary and the sources of requirements from the stakeholder analysis. Technical prescriptions belong in it only if they are genuine requirements; otherwise they restrict competition unnecessarily.
Watch for prior involvement
Consultants writing a specification for a contracting authority should know the rules on prior involvement before bidding in the later tender.