doctrine2/manual/docs/Coding standards - Naming Conventions - Classes.php

<ul>
<li \>The Doctrine ORM Framework uses the same class naming convention as PEAR and Zend framework, where the names of the classes directly 
map to the directories in which they are stored. The root level directory of the Doctrine Framework is the "Doctrine/" directory, 
under which all classes are stored hierarchially.
</ul>
<ul>
<li \>Class names may only contain alphanumeric characters. Numbers are permitted in class names but are discouraged. 
Underscores are only permitted in place of the path separator, eg. the filename "Doctrine/Table/Exception.php" must map to the class name "Doctrine_Table_Exception".
</ul>
<ul>
<li \>If a class name is comprised of more than one word, the first letter of each new word must be capitalized. Successive capitalized letters 
are not allowed, e.g. a class "XML_Reader" is not allowed while "Xml_Reader" is acceptable.
</ul>