Update mxml.md
edit in progress
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+++ b/features/mxml.md
@@ -28,7 +28,7 @@
Most Royale applications have an MXML file as the main file in the app. It provides the structure of the application. A simple main MXML file might look like this:
-```mxml
+```
<?xml version="1.0" encoding="utf-8"?>
<j:Group xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:j="library://ns.apache.org/royale/jewel"
@@ -57,3 +57,19 @@
## What goes where ##
The more complex the application is, the more things the main MXML file needs to be able to support and do. Typically, a developer organizes the file so it is easy to locate things in it. Some elements must be inside certain tags, and for others you have a lot of flexibility. However, if you are working in a team, it is good to have an agreement about what goes where so nobody wastes time or adds in code that already exists somewhere else in the file.
+
+### What your file _must_ have ###
+
+Your main MXML file has two essential elements:
+
+**the header**: In the example above, the header tag `<?xml version="1.0" encoding="utf-8"?>` has two parts:
+
+ - **XML declaration**: this tells the compiler what version of XML the file is using. 1.0 is the default; but since other versions exist, you have to specify it.
+ - **The encoding**: this tells the compiler what text encoding to use to translate the bits of code into letters and numbers to displahy in the UI. The default is `utf-8`, but some applications use different encodings that suit their specific needs.
+
+
+**The main tag**: This tag includes everything else on the page. For a full application, it usually starts `<js:Application...` and ends as the last line of the file: `</js:Application>`.
+
+You write the rest of the page's contents within this tag, and the tag's attributes are very important for configuring and launching the application
+
+### What your file _may_ have ###
