README.md in mosql-0.1.2 vs README.md in mosql-0.2.0

@@ -51,12 +51,19 @@
 
 
     mongodb:
       blog_posts:
         :columns:
-        - _id: TEXT
-        - author: TEXT
+        - id:
+          :source: _id
+          :type: TEXT
+        - author_name:
+          :source: author.name
+          :type: TEXT
+        - author_bio:
+          :source: author.bio
+          :type: TEXT
         - title: TEXT
         - created: DOUBLE PRECISION
         :meta:
           :table: blog_posts
           :extra_props: true
@@ -65,19 +72,45 @@
 mapping
 
     <Mongo DB name> -> { <Mongo Collection Name> -> <Collection Definition> }
 
 Where a `<Collection Definition>` is a hash with `:columns` and
-`:meta` fields. `:columns` is a list of one-element hashes, mapping
-field-name to SQL type. It is required to include at least an `_id`
-mapping. `:meta` contains metadata about this collection/table. It is
+`:meta` fields.
+
+`:columns` is a list of hashes mapping SQL column names to an hash
+describing that column. This hash may contain the following fields:
+
+  * `:source`: The name of the attribute inside of MongoDB.
+  * `:type`: (Mandatory) The SQL type.
+
+
+Use of the `:source` attribute allows for renaming attributes, and
+extracting elements of a nested hash using MongoDB's
+[dot notation][dot-notation]. In the above example, the `name` and
+`bio` fields of the `author` sub-document will be expanded, and the
+MongoDB `_id` field will be mapped to an SQL `id` column.
+
+At present, MoSQL does not support using the dot notation to access
+elements inside arrays.
+
+As a shorthand, you can specify a one-elment hash of the form `name:
+TYPE`, in which case `name` will be used for both the source attribute
+and the name of the destination column. You can see this shorthand for
+the `title` and `created` attributes, above.
+
+Every defined collection must include a mapping for the `_id`
+attribute.
+
+`:meta` contains metadata about this collection/table. It is
 required to include at least `:table`, naming the SQL table this
 collection will be mapped to. `extra_props` determines the handling of
 unknown fields in MongoDB objects -- more about that later.
 
 By default, `mosql` looks for a collection map in a file named
 `collections.yml` in your current working directory, but you can
 specify a different one with `-c` or `--collections`.
+
+[dot-notation]: http://docs.mongodb.org/manual/core/document/#dot-notation
 
 ## Usage
 
 Once you have a collection map. MoSQL usage is easy. The basic form
 is: