@subheading Goals

This section organizes default design models for different major
releases of CentOS Distribution.

@subheading Description

In order to better understatand how this visual manifestation is
organized, it is necessary to consider what The CentOS Distribution is
and how it is released.

@subsubheading The CentOS Distribution

The CentOS Distribution is an Enterprise-class Linux Distribution
derived from sources freely provided to the public by a prominent
North American Enterprise Linux vendor. The CentOS Distribution
conforms fully with the upstream vendors redistribution policy and
aims to be 100% binary compatible. (The CentOS Project mainly changes
packages to remove upstream vendor branding and artwork.)

The CentOS Distribution is developed by a small but growing team of
core developers.  In turn the core developers are supported by an
active user community including system administrators, network
administrators, enterprise users, managers, core Linux contributors
and Linux enthusiasts from around the world.

@subsubheading The CentOS Distribution Release Schema

The upstream vendor has released 4 versions of their
@acronym{EL,Enterprise Linux} product that The CentOS Project rebuilds
the freely available SRPMS for.  The upstream vendor releases security
updates as required by circumstances. The CentOS Project releases
rebuilds of security updates as soon as possible. Usually within 24
hours (our stated goal is with 72 hours, but we are usually much
faster).

The upstream vendor also releases numbered update sets for major
versions of their EL product from 2 to 4 times per year. There are new
ISOs from the upstream vendor provided for these update sets.  Update
sets will be completed as soon as possible after the upstream vendor
releases their version @dots{} generally within 2 weeks. The CentOS
Project follows these conventions as well, so CentOS-3.9 correlates
with EL 3 update 9 and CentOS-4.6 correlates with EL 4 update 6,
CentOS-5.1 correlates to EL 5 update 1, etc.

One thing some people have problems understanding is that if you have
any CentOS-3 product and update it, you will be updated to the latest
CentOS-3.x version.  

The same is true for CentOS-4 and CentOS-5. If you update any CentOS-4
product, you will be updated to the latest CentOS-4.x version, or to
the latest CentOS-5.x version if you are updating a CentOS-5 system.
This is exactly the same behavior as the upstream product.  Let's
assume that the latest EL4 product is update 6. If you install the
upstream original EL4 CDs (the ones before any update set) and upgrade
via @command{yum}, you will have latest update set installed (EL4
update 6 in our example). Since all updates within a major release
(CentOS-2, CentOS-3, CentOS-4, CentOS-5) always upgrade to the latest
version when updates are performed (thus mimicking upstream behavior),
only the latest version is maintained in each main tree on The CentOS
Mirrors (@url{http://mirrors.centos.org/}).

There is a CentOS Vault (@url{http://vault.centos.org/}) containing
old CentOS trees. This vault is a picture of the older tree when it
was removed from the main tree, and does not receive updates. It
should only be used for reference. 

The CentOS Distribution visual style is controlled by image files.
These image files are packaged inside The CentOS Distribution and made
visible once such packages are installed and executed. The way to go
for changing The CentOS Distribution visual style is changing all
those image files to add the desired visual style first and later,
repackage them to make them available inside the final iso files of
CentOS Distribution.

@subheading Usage

Sometimes, between major releases, image files inside packages can be
added, removed or just get the name changed. In order to describe such
variations, the design models directory structure is organized in the
same way the variations are introduced (i.e., through The CentOS
Distribution Release Schema).  So, each major release of The CentOS
Distribution has its own design model directory structure.

When a new package/component is added to one or all the major releases
of The CentOS Distribution, a design model directory structure for
that component needs to be created. Later, it is filled up with
related design models. Design models are created for each image file
inside the component that need to be rebuilt in order to set the
visual style and brand information correctly.

When a package is removed from one or all major releases of The CentOS
Distribution, the design model directory structure releated to that
package/component is no longer used.  However, it could be very useful
for historical reasons.  Also, someone could feel motivation enough to
keep himself documenting it or supporting it for whatever reason.

@itemize
@item --- @strong{Removed}(xref:Directories trunk Identity Models Themes Default Distro
5) ---.
@end itemize

@subheading See also

@itemize
@item --- @strong{Removed}(ref:Directories trunk Identity Models Themes Default) ---.
@item @ref{Directories trunk Identity Models Themes}.
@item @ref{Directories trunk Identity Images Themes}.
@item @ref{Directories trunk Identity}.
@item @ref{Directories trunk}.
@end itemize