Purpose ‐ The purpose of the paper is to design a model and tools that are capable of representing and handling personal knowledge in different degrees of structuredness and formalisation, and usable and extensible by end-users. Design/methodology/approach ‐ This paper presents the results of analysing literature and various data models and formalisms used to structure information on the desktop. Findings ‐ The unified data model (CDS) is capable of representing structures from various information tools, including documents, file systems, hypertext, tagging and mind maps. The five knowledge axes of CDS are identity, order, hierarchy, annotation and linking. Research limitations/implications ‐ The CDS model is based on text. Extensions for multimedia annotations have not been investigated. Practical implications ‐ Future personal knowledge management (PKM) tools should take the mentioned shortcoming of existing PKM tools into account. Implementing the CDS model can be a way to make PKM tools interoperable. Originality/value ‐ This paper presents research combining cognitive psychology, personal knowledge management and semantic web technologies. The CDS model provides a way to let end-users work on different levels of granularity and different levels of formality in one environment.