The International Association for Volcanology and Chemistry of Earth's Interior (IAVCEI), The World Organization of Volcano Observatories (WOVO), and the Global Volcano Model (GVM) have sanctioned GVP to assign numbers and primary names
to the world's volcanoes. The purpose of the numbers is to prevent ambiguity regarding the name and location of volcanoes that may have non-unique names, or that are known by multiple names. The original VNums were based on a system developed in the 1950's for the IAVCEI Catalog of Active Volcanoes of the World (CAVW). GVP policy had been to embed significant geographical, historical, and age information in the numbers. As a result GVP often changed VNums, most frequently to accommodate newly recognized volcanoes in a particular geographical region, which over time undermined the goal of preventing ambiguity.