By convention, plugins and vendor libraries are typically located in `app-path/libraries` or
`/libraries` (the former may override the latter). By default, `Libraries` will use its own
autoloader for all plugins and vendor libraries, but can be configured to use others on a
per-library basis.

`Libraries` also handles service location. Various _types_ of classes can be defined by name,
using _class patterns_, which define conventions for organizing classes, i.e. `'models'`, which
maps to `'{:library}\models\{:name}'`, which will find a model class in any registered app,
plugin or vendor library that follows that path (namespace) convention. You can find classes by
name (see the `locate()` method for more information on class-locating precedence), or find all
models in all registered libraries (apps / plugins / vendor libraries, etc). For more information
on modifying the default class organization, or defining your own class types, see the `paths()`
method.

#### Auto-loading classes

Lithium defines several rules, conventions and recommendations for naming and organizing classes.
The autoloader itself conforms to the [PHP Interoperability Group's draft
specification](http://groups.google.com/group/php-standards/web/psr-0-final-proposal). While the
autoloader will load any classes conforming to that specification, Lithium itself follows
additional constraints, which are also recommended for Lithium applications, libraries and
extensions, and are as follows:

 - Each library must exist in a top-level vendor namespace
- Each top-level vendor namespace must define a set of sub-packages, and should not directly
  contain classes
- Namespace names must be lowercased and under_scored
- Class names must be CamelCased

Any libraries registered by calling `Libraries::add()` which follow the autoloader's will have
their classes automatically loaded when referenced.