DOC: design index page; language corrected, but a few rewrites.

TODO: Backend, needs just a little more, not much, e.g.:
      Area where low-level  memory, hardware i/o, etc occur => here
      is where real gain in efficiency through modern algorithms can occur,
      thus, achieving another goal of Lumiera: efficient & runs on all kinds
      of hardware!

doc/design/index.txt

@@ -25,31 +25,31 @@ may be used to do any task on video (and audio?), even unrelated to video editin
 
 .Workflow
 *****************
-The word Workflow is used to name the way tasks can be achieved in an
+The word ``workflow'' is used to name the way tasks can be achieved in an
 application. Any operation in Lumiera must be possible in the most suitable and
-stringent fashion. The Workflow is closely related to how flexible the GUI is
-but also the concern of deeper and more technical parts of the application.
+stringent fashion. The workflow is closely related to how flexible the GUI is
+but is also the concern of deeper and more technical parts of the application.
 *****************
 
 
 Overview
 --------
 
-The internal structure of Lumiera is divided in numerous subsystems.  This
-overview will try to go through the elements from the highest to the lowest
-piece of the structure.  They can be categorized into three main categories plus
-extra components:
-
+The internal structure of Lumiera is divided into numerous subsystems.  This
+overview will provide a general description of the major areas that make up
+Lumiera from the highest down to the lowest level. Lumiera can be considered to
+be composed of three main areas with an additional extra components. We discuss
+theses areas below.
 
 Graphical User Interface
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
-User interfaces are basically included as a plugin, consequently it is possible
-to interface with Lumiera through scripts. It is also possible to create
-specialised GUIs.  The interface is the closest component to the user, it is
-purely visual. There the user manipulates, organizes, loads, configures all
-sorts of data, especially MObjects (media objects) and Assets. These elements
-are contained within a structure called the Session. +
+User interfaces are basically implemented as a plugin. As a consequence, it is
+possible to interface with Lumiera through scripts. It is also possible to create
+specialised GUIs.  The interface is the closest component to the user. It is
+a purely visual interaction with the user. There the user manipulates,
+organizes, loads, configures all sorts of data, especially MObjects (media
+objects) and Assets. These elements are contained within a structure called the Session. +
 -> link:gui/index.html[GUI design documents]
 
 
@@ -64,8 +64,8 @@ a component known as _the Builder_ assembles the contents of this model and tran
 them to form a network of nodes, which can be _performed_ efficiently for rendering.
 Often, we refer to this node structure as the ``low-level model''. On rendering or
 playback, the Proc-layer is responsible for accessing this node structure to 
-generate individual _frame render jobs,_ ready to be handed over to the backend
-for the actual rendering calculations. +
+generate individual _frame render jobs,_ ready to be handed over to the backend, which
+performs the actual rendering calculations. +
 -> more about the link:model/index.html[Model] +
 -> design of the link:engine/index.html[Engine] subsystem
 
@@ -74,34 +74,35 @@ for the actual rendering calculations. +
 The Backend
 ~~~~~~~~~~~
 
-The backend uses the Low-level model and the _render jobs_ generated by Proc.
-It actually performs the the rendering operations and makes a heavy use of the
+The backend uses the low-level model and the _render jobs_ generated by Proc.
+It actually performs the rendering operations and makes heavy use of the
 Input/Output System for accessing media content and sending generated data to
-the screen or external output. +
+the screen or to external output. +
 -> link:backend/index.html[Backend design level documents] +
 -> link:{ldoc}/technical/backend/index.html[technical documentation] +
 
 
-Extra components
+Extra Components
 ----------------
 
 The Application
 ~~~~~~~~~~~~~~~
 
 The application controls the initialization and shutdown procedures as well as
-loading external elements like plugins that are widely used. It acts as a framework
-to support the operation of the core components. This framework is complemented by
-a library of commonly used components, algorithms and data structures. +
+loading external elements such as plugins, which are widely used throughout
+Lumiera. It acts as the framework which supports core component operations. This
+framework is complemented by a library of commonly used components, algorithms and data structures. +
 -> link:application/index.html[Application framework]
 
 
 link:plugins/index.html[Plugins]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Plugins play an important role within Lumiera since the application relies heavily
-existing implementations and external libraries. Moreover, the application is envisioned
-to be configurable and can be extended in various ways; whenever some extension isn't permanent
-or will be used only on demand, it is packaged as separate module into a plug-in. For example,
-the GUI of Lumiera is a plugin. +
+Plugins play an important role within Lumiera since the application relies
+heavily on current FLOSS implementations and external libraries. Moreover, the
+application is envisioned to be configurable and can be extended in various
+ways; whenever some extension isn't permanent or will be used only on demand, it
+is packaged as a separate module into a plug-in. For example, the GUI of Lumiera
+is a plugin. + 
 -> design doruments regarding the link:plugins/index.html[Plugins]