Error(1,1)mdssys/mdx/componentType.rdf: XML-20108: (Fatal Error) Start of root element expected.

 Error(1,1)mdssys/mdx/componentType.rdf<Line 1, Column 1>: XML-20108: (Fatal Error) Start of root element expected.

Sometimes when we build Oracle SOA project we get the above error. To resolve this issue just go to those file where this error is coming you can see this from compiler and remove those file or add following in those files 

<xml version="1.0" encoding="UTF-8"/> 

Save it and rebuild the code again and this error will be no more.