The field of software development has evolved significantly since its early days, with the task of a programmer being to relay instructions to underlying hardware, but now focusing on solutions at a higher level of abstraction. Model-Driven Engineering (MDE) is a discipline that promotes models as first-class artifacts in the engineering process, raising the level of abstraction and using metamodels to describe domain-specific data. The Eclipse Modelling Framework (EMF) provides a framework for defining metamodels and tooling to work with them programmatically in Java, including Ecore as its meta-metamodel. Model Management is the process of acting upon models, which includes tasks such as visualisation, querying, validation, comparison, merging, migration, transformation, and text generation. The de-facto language used for validating models beyond the capabilities of Ecore is the Object Constraint Language (OCL). Epsilon provides a family of task-specific model management languages built on top of a common core query language called EOL, which supports multiple modelling technologies and is not bound to EMF, providing an all-in-one solution for model management.