FlexDoc/XML XSDDoc is described as 'High-performance XML Schema Documentation Generator with diagrams. Generates by any number of input XSD files a highly-navigable Javadoc-like HTML as well as single-file HTML/RTF. Diagrams generated by own diagramming engine look as those of XMLSpy'. There are three alternatives to FlexDoc/XML XSDDoc for Windows, Linux and Mac. The best alternative is Altova XMLSpy. Other great apps like FlexDoc/XML XSDDoc are Oxygen XML Editor (Paid) and Liquid Studio (Paid).