This book provides an introduction to the basics of XBRL targeting specifically technical people: developers, software engineers, data scientists. It leaves business considerations or concrete applications aside, since they are covered extensively in other books. While it includes coverage of the XML syntax of XBRL, most of the book is focused on the tabular data model specific to XBRL, in a way compatible with the new Open Information Model currently under development. It does not require any knowledge of XML, as the sections on XML syntax can conveniently be skipped without understanding XBRL any less. This provides a higher level of abstraction that makes it easier to learn XBRL without having to deal with the complexities and intricacies of XML technologies. This makes the book accessible to people with other backgrounds than IT, such as accountants, if they enjoy diving into the technical side. This first edition covers instances, facts, taxonomies, schemas and linkbases, concepts, abstracts, label linkbases, presentation networks, calculation networks and some patterns commonly used in practice (SEC) such as hierarchies, roll-ups and text blocks, relying on Charles Hoffman's work.