The paper discusses the challenges of categorising documents and "items of the world" to promote knowledge sharing in large communities of interest. We present the DOCMA method (Document and Item-based Model for Action) dedicated to end-users who have minimal or no knowledge of information science. Community members can elicit structure and indexed business items stemming from their query including projects, actors, products, places of interest, and geo-situated objects. This hybrid method was applied in a collaborative Web portal in the field of sustainability for the past two years.