This paper describes the work performed to define the characteristics, functionalities and potential algorithms in order to ensure the interoperability of the different markets and platforms developed by TSOs and DSOs across Europe: 1- Specification: Definition of the overall system architecture to be implemented in each demonstration site. 2- Market block: Definition of the relation between central, regional and local markets, as well as the structure (bidding times, market horizon, clearing frequency, etc.) and clearing algorithms for them. 3- Network block: Description of network monitoring and operation tools to determine the needs of system operators. Identification, upon existing tools for monitoring and operating distribution and transmission grid, of the generic requirements and functionalities of these tools. The purpose of these tools is the identification of grid issues which are then used to quantify the flexibility requirements for the local and/or wholesale markets for system services. 4- Aggregation block: Analysis and definition of types of algorithms and mathematical models to be used by aggregators to: a. estimate the flexibility available from the different large-scale and small-scale units included in their portfolios, b. translate those flexibilities into offers to be sent to the local, regional and/or wholesale markets for system services, and c. allocate the flexibility to the different units once the market clearing result is received from DSOs and TSOs. 5- Standardisation: Definition of the information exchange requirements between the different blocks by means of the Smart Grid Architecture Model (SGAM) methodology. The definition of these standard interfaces is done in terms of information models, timing requirements and interaction sequences. 6- Innovative enabling technologies: Activities which allow to determine, how, to what extent and under which conditions innovative enabling technologies may incentivize consumers’ participation to energy marketplace.