The current ConceptNet API has the ability to access the database we call “ConceptNet 4”. Once this API is stable enough, we’ll call it ConceptNet 4.0.
The answer from 30,000 feet up is simple: It’s Django.
Django is a Python framework for working with databases and web applications. All of ConceptNet is represented as Django models that interact with each other and with a database. We don’t use the web application part – not here, at least – but we provide the appropriate hooks so that ConceptNet can power a Django web application. (Because it does. It’s at http://openmind.media.mit.edu.)
The code is divided into a few main modules, or apps:
Each app contains several models, representing objects that are stored in a database. The information in ConceptNet is represented by these models and their relationships to each other.