Abstract. Active mathematical documents are distinguished from traditional paper-oriented ones by their ability to interactively adapt to a reader’s inputs. This includes changes in the presentation of the content of the document as well as changes of that content itself. We have developed the JOBAD architecture, a client/server infrastructure for active mathematical documents. A server-side module generates active documents, which a client-side JavaScript library makes accessible for user interaction. Further server-side modules – in the same backend, or distributed web services – dynamically respond to callbacks invoked when the user interacts with the client. These three components are tied together by the JOBAD active document format, which backwardscompatibly enhances MathML by information about interactivity. JOBAD is designed to be modular in the specific web services offered. As examples, we present folding and elision in mathematical expressions, type and definition l...