The proposed Augmented Reality (AR) Learning Experience Model (LEM) specifies how to represent activities conducive to developing or upgrading knowledge@ skills@ and other abilities in a standardized interchange format. The interchange format includes a description of the activity and of the environment and context in the actual workplace in which it can be executed. It aims to lower entry barriers for authoring of learning experience spanning real world interaction using sensors and computer vision@ and web applications. For example@ astronauts can be trained using such Augmented Reality learning experiences while on the ground or when up in space@ practicing how to perform the assembly procedure of a temporary stowage rack. The AR training system executes the learning activity (represented with this specification) to provide procedural guidance live and in context@ directing attention to relevant parts and overlaying visual instruction and 3D animations to explain step-by-step what needs to be done. For example@ aeronautics service technicians in training can build expertise with such Augmented Reality learning experience in how to rig an aircraft engine@ receiving activity guidance on how to adjust the various components associated with the control system@ in order to learn how to optimize engine performance. For example@ doctors in training can benefit from an Augmented Reality learning experience when used to learn diagnostic procedures for detectingpulmonary embolismon a patient simulator@ being guided and receiving explanatory support for different conditions and the way they would show on different imaging technologies. Purpose ARLEM provides an overarching integrated conceptual model and the according data model specifications for representing activities@ learning context and environment (aka 'workplace')@ while linking with other data model components needed for AR-enhanced learning activities. Separation of slow-changing data for environment description from fast-changing data for step-by-step guidance is intended. Isolation in linked@ but physically separate interchange formats@ facilitates efficient handling and storage. The standard defines the required data models and modeling languages and their bindings to the chosen representation format XML [B2]. Using XML for representation reduces complexity of authoring AR learning experiences to a similar level as required for creating web pages. This interoperability specification helps to open up the market for AR learning resources@ adding interchangeable component products to otherwise monolithic Augmented Reality learning apps. It is a building block for the creation of repositories and online marketplaces for Augmented Reality enabled learning content. Specific attention was paid to supporting reuse and repurposing of existing learning contents to cater for 'mixed' experiences combining real-world learner guidance with the consumption (or production) of traditional contents such as instructional video material or learning apps and widgets.