Louis Rosenfeld and Peter Morville defined the ‘three circles of information architecture’ as content, users and context of use.
Users – it’s very important to know your users, their needs, how they use information, etc.
Content – who creates the content? is it centralised or decentralised? is it text? or other media?
Context – what are the goals? and the resources? the company culture and politics?
Reference: Rosenfeld and Morville, “Information Architecture for the World Wide Web.” , O’Reilly publications