.. index:: diagrams; class
.. index:: pair: Model Composition; classes
.. index:: classes; core


.. _Class-Diagrams:


Class Diagrams
--------------

The following sections present Class Diagrams for Model Composition Classes
(core classes), built-in Variable Classes, Factory Classes, and Server Classes.


Model Composition Classes
===========================

The figure `Class Diagram of Core Classes`_ shows the classes that are the
building blocks of a *model*. A model is a hierarchical structure with an
:term:`Assembly` at its root. Within the Assembly is some number of
:term:`Components`, and at least one :term:`Driver` which is a special type of
Component that iterates over a :term:`Workflow` until some condition is met. A
Workflow controls the execution order of the components that it references.
The components have attributes that can be linked to attributes on other
components. An Assembly is a Component, which means that it can be contained
within another Assembly. This allows for the creation of hierarchical models
with many levels of nested Assemblies. Workflows can contain Drivers. This
allows for many levels of nested iteration *within the same Assembly.*


.. _`Class Diagram of Core Classes`:

.. figure:: ../generated_images/ModelClasses.png
   :align: center

   Class Diagram of Core Classes


.. index:: built-in Trait classes
.. index:: classes; built-in Trait 
.. index:: Traits


Classes for Validation and Conversion of Component Attributes
=============================================================

Validation and conversion of Component attributes is done using the Traits_
package. You can define your own custom traits by inheriting from TraitType
and overriding the ``validate()`` function. :term:`Traits` also has built-in
support for creation of graphical editors for each trait. The documentation
claims that traits uses something called pyface to provide a sort of
generalized UI layer that can be tied to various GUI libraries on the back end
but it's not clear at this point whether this functionality will work in the
context of a web GUI.  

In the class diagram below, classes that are part of the enthought.traits
package are gray, and our custom traits are white. Notice that there are two
*Float* classes. One is Enthought's and one is our version, which includes
units and range checking.


.. _Traits: http://code.enthought.com/projects/traits/documentation.php

.. figure:: ../generated_images/VariableClasses.png
    :align: center
    
    Class Diagram of Built-in Traits
    
       
.. index:: pair: Factory; classes   

Factory Classes
===============

It is important to give location transparency to the process of object creation,
and using Factory classes lets users do that in an extensible way. The creation
of an object with a specific type and version will be requested, and the
framework will create the object. This creation process could involve spawning a
remote process, instantiating a remote version of the object, and creating a
local proxy to represent the remote object, or it could be a simple import and a
constructor call. To the caller, it makes no difference. The call returns a
local python object, and the true location of the object requested doesn't
matter.


.. figure:: ../generated_images/CreatorClasses.png
   :align: center

   Class Diagram of Factory Classes
 
   
.. index:: pair: Server; classes   
.. index:: ServerManager
   
   
Server Classes
==============

Simulations are run in one or more :term:`ObjServer` processes, possibly distributed among
multiple hosts. ObjServer processes are created by :term:`ObjServerFactory`, either dynamically
when a particular component type is needed which is not supported in the main simulation server,
by the user when starting a new simulation via the ServerManager, which acts as a portal, or by
the user from the command line.

The base Server class provides a common mechanism for configuring network
protocols and services, while the Simulation class contains the top-level
component and the ResourceAllocationManager for this simulation object.


.. figure:: ../generated_images/ServerClasses.png
   :align: center

   Class Diagram of Server Classes

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