One solution is to simply rename one of the Address element types -- for example, we could rename the second element type IPAddress. However, this is not a useful long term solution. One of the hopes of XML is that people will standardize XML languages for various subject areas and write modular code to process those languages. By reusing existing languages and code, people can quickly define new languages and write applications that process them. If we rename the second Address element type to IPAddress, we will break any code that expects the old name. A better answer is to assign each language (including its Address element type) to a different namespace. This allows us to continue using the Address name in each language, but to distinguish between the two different element types. The mechanism by which we do this is XML namespaces. Note that by assigning each Address name to an XML namespace, we actually change the name to a two-part name consisting of the name of the XML namespace plus the name Address. This means that any code that recognizes just the name Address will need to be changed to recognize the new two-part name. However, this only needs to be done once, as the two-part name is universally unique.