## 2 The Marine Information System  
In this section, we briefly recall the Marine Information System (MIS) [8], which is used in this paper as a baseline platform for the integration of Volunteered Geographical Information (VGI). The MIS has been designed to provide an effective and feasible detection and management of marine pollution events, by integrating and analyzing data acquired by disparate monitoring resources, exploited to get useful and relevant information about the sites under surveillance. The main task of the MIS is to serve as a catalyst for integrating data, information and knowledge from various sources pertained to the marine areas of interest, by means of adequate Information Technology (IT) tools. More precisely, following the Infrastructure for Spatial Information in the European Community (INSPIRE) and Global Monitoring for Environment and Security (GMES) recommendations [22], the MIS has been conceived as an interconnected group of subsystems for performing data storage, decision-support, data mining and analysis over data warehouses, as well as a web portal with GIS functionalities for the access and usage of products and services released to end-users.  
As an output of designing, a list of general subsystems has been identified, having the following roles:  
1. SAR image acquisition, devoted to the management of all the information workflow related to SAR image acquisition and processing.
2. Hyperspectral-thermal image analysis, devoted to the management of the information workflow related to the analysis of the hyperspectral images acquired by airborne sensors.
3. Mathematical simulation, devoted to the provision of simulation results on the basis of models for 3D hydrodynamics, waves, oil-spill transport and weathering.
4. Integrated communication system for the management of geographically-located devices, to provide an information infrastructure, able to transfer data between the actors located in the geographic area to be monitored and the MIS.
5. AUVs management and data analysis. AUVs are able to carry on board special sensors (e.g., including an E-nose for assessing the quality of water in the area under monitoring).
6. Marine traffic monitoring, devoted to the collection of Automatic Identification System (AIS) data and to the provision of services for accessing, retrieving and visualizing them. AIS technology offers an efficient and practical way to track vessels [23; 24].
7. Data mining and warehousing, devoted to the collection and analysis of historical data by means of advanced statistical tools for discovering and understanding relationship among the data (e.g., between traffic density and the probability of occurrence of pollution events) and supporting strategic decision-making.
8. Environmental Decision Support System (EDSS), committed to the identification and monitoring of possible oil slick events by analyzing and combining the multi-source data coming from the different data acquisition and processing subsystems of the MIS.  
In particular, by integrating specific analysis models that are strictly connected to all the devices and subsystems, the EDSS processes the environmental data acquired by the various monitoring resources by applying simulation and optimization models for site characterization and observation and detects possible marine pollution events by applying risk analysis models. The high level MIS architectural design is shown in Figure 1. The core components are interconnected thanks to a middleware layer that achieves communication and cooperation among the various units. All data gathering service (including AUV, AIS, image analysis and mathematical simulation) are implemented using a set of reconfigurable service units that are in charge of fetching data from the providers and transforming them into a suitable format to achieve interoperability with the other MIS components.