Update README.md

README.md

@@ -1,2 +1,35 @@
 # anseml ![](https://github.com/akarpovskii/anseml/workflows/Clojure%20CI/badge.svg)
-ANother S-Expression Markup Language
+ANSEML is ANother S-Expression Markup Language inspired by XML format.
+
+The library provides a simple API to work with documents and a tool to convert the document to HTML format.
+
+The document format is pretty straightforward.
+- Each ANSEML document has exactly one single root element, which encloses all the other elements.
+- Each element may or may not have a set of attributes.
+
+More specifically, the format is following:
+
+```
+(:tag-name
+    attr-map?
+    body)
+```
+
+Where `attr-map?` is an associative array of `{ key value }` pairs,
+where `key` is `keyword` and `value` is one of the following _primitives_: `string, integer, float`; and `body` contains zero or more _primitives_ or enclosed elements.
+
+Here are few examples:
+
+```
+(:root
+    { :id "Root" }
+    "Here is a number:" 123
+    "And here is the text:"
+    (:text
+        "Some text")
+    :br
+    (:text
+        "Another text"))
+```  
+
+Note that you don't need to put parenthesis around the element consisting only of a tag-name.