Modern Information and Communication Technologies are definitely a key factor to develop the green and sustainable applications that the so-called 'smart city' needs. Effective management of resources, gathering and interpreting data as well as ecological considerations are prerequisites to turn such a vision into reality. The European FP7 project DIMMER address these issues by providing a flexible Internet of Thing platform for application development and data integration, exploiting information about buildings, energy distribution grids and user behaviors. Among those applications, the possibility to real-time access and aggregate information about building environmental characteristics and energy consumption enables the optimization of energy management and control, as well as the user's awareness about, which is the scope of the DIMMER project

Following the Smart City views, citizens, policy makers and energy distribution companies need a reliable and scalable infrastructure to manage and analyse energy consumption data in a city district context. In order to move forward this view, a city district model is needed, which takes into account different datasources such as Building Information Models, Geographic Information Systems and real-time information coming from heterogeneous devices in the district. The Internet of Things paradigm is creating new business opportunities for low-cost, low-power and high-performance devices. Nevertheless, because of the "smart devices" heterogeneity, in order to provide uniform access to their functionalities, an abstract point of view is needed. Therefore, we propose an distributed software infrastructure, exploiting service-oriented middleware and ontology solutions to cope with the management, simulation and visualization of district energy data.

Data management has been one of the most interesting research fields within the smart city framework over the last years, with the aim of optimizing energy saving at district level. This topic involves the creation of a 3D city model considering heterogeneous datasets, such as Building Information Models (BIMs), Geographical Information Systems (GISs) and System Information Models (SIMs), taking into account both buildings and the energy network. Through the creation of a common platform, the data sharing was allowed starting from the needs of the users, such as the public administrator, the building manager and the energy professional. For this reason, the development of a District Information Modelling (DIM) methodology for the data management, related to the energy saving and CO2 emission, is considered the focus of this paper. It also presents a specific tool developed for the comparison of energy data in a selected district: the Benchmarking Tool.