The PARSER may not be able to access VARIOUS external entities or schema documents (imported, included etc...) available on the Internet, such as the Schema for Schemas "http://www.w3.org/2001/XMLSchema.xsd" or the schema defining xml:base, xml:lang attributes etc... "http://www.w3.org/2001/xml.xsd" or any other external entity available on the Internet. There are various reasons ONE could EXPERIENCE such a problem. 

One of the reasons could be that your proxy settings do not allow the parser to make URL connections through a proxy server. To solve this problem, before parsing a document, the application must set the TWO system properties: "http.proxyHost" and "http.proxyPort". Another reason could be due to strict firewall settings that do not allow any URL connection to be made to the outside web. The problem may also be caused by a server that is offline or inaccessible on the network, preventing documents hosted by the server from being accessed.

The parser may not be able to access various external entities or schema documents (imported, included etc...) available on the Internet, such as the Schema for Schemas "http://www.w3.org/2001/XMLSchema.xsd" or the schema defining xml:base, xml:lang attributes etc... "http://www.w3.org/2001/xml.xsd" or any other external entity available on the Internet. There are various reasons one could experience such a problem. 

One of the reasons could be that your proxy settings do not allow the parser to make URL connections through a proxy server. To solve this problem, before parsing a document, the application must set the two system properties: "http.proxyHost" and "http.proxyPort". Another reason could be due to strict firewall settings that do not allow any URL connection to be made to the outside web. The problem may also be caused by a server that is offline or inaccessible on the network, preventing documents hosted by the server from being accessed.