source code analysis. Source code analysis is the automated testing of source code for the purpose of debugging a computer program or application before it is distributed or sold. Microsoft Excel Open XML Document. XLSX is a file extension for an open XML spreadsheet file format used by Microsoft Excel. Microsoft introduced the open XML standard to Microsoft Office in 2007 after a push from business users who saw the value in an open file format for transferring data between applications and other areas of working with the files.