default namespace = ""

start =
  element configuration {
    element packageRestore { add+ }?,
    (element config { add }
     | element packageSourceMapping {
         element packageSource {
           attribute key { xsd:NCName },
           element package {
             attribute pattern { text }
           }
         }+
       }
     | element packageSources {
         element clear { empty },
         add+
       })+
  }
add =
  element add {
    attribute key { xsd:NCName },
    attribute protocolVersion { xsd:integer }?,
    attribute value { xsd:anyURI }
  }