| HBS Working Paper Series
Hidden Structure: Using Network Methods to Map Product Architecture
In this paper, we describe an operational methodology for characterising the architecture of technical systems and demonstrate its application to a sample of software releases. Our methodology is based on network graphs and allows us to identify define three fundamental architectural patterns, which we label core-periphery, multi-core, and hierarchical. Applying our methodology to a sample of 1,286 software releases from 17 applications, we find that 67 – 89% of releases possess a "core-periphery" architecture under our classification scheme. This architecture is characterized by having a single dominant cyclic group (the Core) that is large relative to other cyclic groups and above a threshold with respect to system size. We find that the size of the Core varies widely, even for systems that perform the same function. These differences appear to be associated with different models of development—open, distributed organizations develop systems with smaller Cores, while closed, co-located organizations develop systems with larger Cores. Our findings represent a first step in establishing some "stylized facts" about the fine-grained structure of large, real-world technical systems.