This Milestone is an interim report of the activities carried out within IPERION HS Task 6.3 (Interoperability of instrumentation and digital documentation in IPERION HS). It provides an update of the description of the task and a clear definition of its scope. It also describes the three main areas of work: the Data Management Plan for IPERION HS, identifying tools for metadata capture and presentation, and the development of a practical approach to the modelling the capture of the metadata required to achieve an appropriate level of interoperability. In addition the report proposes an as yet theoretical definition of eight levels of potential interoperability between IPERION HS collections, describes the six proposed stages for the definition and documentation of appropriate metadata for a given examination or analysis, presents the series of metadata models created so far, and provides a detailed description of the tools used. The report also outlines plans for the remainder of the Task as well as presenting a short series of recommendations for future work.