The project stems from the need to integrate environmental issues in the planning and programming decision-making process, as set out at EU level by Directive 2001/42/CE, introducing the Strategic Environmental Assessment (SEA). MAPSHARING deals with the problem of the SEA of plans and programmes, in the cross-border context of the area between Region Friuli Venezia Giulia and the Republic of Slovenia, through the definition of a joint framework of territorial knowledge. To ensure high quality levels, the assessment process is supported by a framework of shared knowledge: to this end, the project envisages the setting up of an operational prototype of a Joint Map of Spatial Knowledge and a Territorial Information Service to store the collected data, so as to make them available to planners and programmers, as well as to disseminate them on-line. The JMSK consists in a system of information maps in the form of a Geographic Information System (GIS): it is, by definition, a shared tool resulting from the participation of several subjects who possess portions of knowledge necessary to its establishment, and also because it is functional to the assessment process and the cooperation actions and to participation in general, where shared and disseminated knowledge is the foundation for any decision to be made. The areas of reference of the TIS are, in Italy, the Provinces of Trieste and Pordenone and the Municipality of Udine (for a total of 58 Municipalities - 2,590 km2), and, in Slovenia, the 7 Municipalities of the Coast-Karst statistical region (1,044 km2). The project aims therefore at outlining the link between information and basic mapmaking and the future cross-border plans, through the definition of shared meanings with respect to complex territorial categories (values, risks, critical points, opportunities) without which any cooperation in the field of planning would not be feasible.