We use probabilistic machine learning to span a new endogenous technology space from patent texts. We then rely on information-theoretic methods to construct measures of technological firm distances -- both fixed and time-varying. Using the latter, we present three sets of findings. First, we observe that industries are becoming more technologically specialised and segregated over time. Second, we identify the emergence of internet companies in the mid-1990s as a distinct group of firms with roots in traditional information and communication technologies. Third, we determine the unique set of time-varying rivals surrounding a focal firm in the endogenous technology space. We demonstrate the validity of this approach by means of a case study of the software company Oracle.