Following rules must apply to all constants used within Doctrine framework:

<ul><li \> Constants may contain both alphanumeric characters and the underscore.</ul>

<ul><li \> Constants must always have all letters capitalized.</ul>

<ul><li \> For readablity reasons, words in constant names must be separated by underscore characters. For example, ATTR_EXC_LOGGING is permitted but ATTR_EXCLOGGING is not.
</ul>
<ul><li \> Constants must be defined as class members by using the "const" construct. Defining constants in the global scope with "define" is NOT permitted.
</ul>
