Preface to the special issue: "Comparing Educational Modelling Languages on the 'Planet Game' Case Study"

People with a background in computer science tend to refer to technical specifications for designing learning as metadata standards. And strictly speaking, they are right. Such educational modelling languages, as specification languages for designing learning opportunities are generically called, take a collection of learning opportunities as its starting point and then 'embellishes' them by allotting to them students and staff in various roles, as well as pertinent background information. These embellishments really are data about the learning opportunities, they explicate who is involved with the opportunities, and what information and services are relevant for them. Indeed, they are data about data, hence metadata. However, such a characterisation amounts to a tremendous underestimation of the power of such educational modelling languages