From Coastal Wiki
Every provider of geoinformation has to offer it by means of an Internet geoservice, which can be achieved by using a Web Map Server, with Standard connections based on OGC Specifications. These services will allow the users to access the geoinformation by means of a WMS Client, to visualize it or to download it (under conditions defined by the provider). A provider can have one or more Web Map Servers containing each one several Services. The different services have to be described by the correspondent Services Metadata, which will be published in a Web Catalogue.
Every provider of geoinformation has to be considered as a “node” within the network of Web Map Servers which form a particular SDI.