Mention an XML printer on the Open Projects page

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@127336 91177308-0d34-0410-b5e6-96231b3b80d8

www/OpenProjects.html

@@ -100,6 +100,13 @@ experience -- it should be easy to cross compile applications, install support
 for new architectures, access different compilers and tools, and be consistent
 across different platforms. See the <a href="UniversalDriver.html">Universal
 Driver</a> web page for more information.</li>
+
+<li><b>XML Representation of ASTs</b>: Clang maintains a rich Abstract Syntax Tree that describes the program. Clang could emit an XML document that describes the program, which others tools could consume rather than being tied directly to the Clang binary.The XML representation needs to meet several requirements:
+  <ul>
+    <li><i>General</i>, so that it's able to represent C/C++/Objective-C abstractly, and isn't tied to the specific internal ASTs that Clang uses.</li>
+    <li><i>Documented</i>, with appropriate Schema against which the output of Clang's XML formatter can be verified.</li>
+    <li><i>Stable</i> across Clang versions.</li>
+  </ul></li>
 </ul>
 
 </div>