This article should give people an introduction into PHPCR. At the end of the article, the user should know enough about the PHPCR to use it in it's own projects. Don't duplicate the doctrine documentation and add some links to the doctrine docs. Take the book/doctrine and book/propel articles of the core docs as an example.

Have a look at cookbook/database/choosing_storage_layer.rst as well and decide what information should go where.

For more information see the wiki: https://github.com/symfony-cmf/symfony-cmf/wiki/Documentation-TOC-(DRAFT)#book

If you don't know enough about Restructured Text, you can also provide your PR in Markdown, HTML or a raw office document and I'll convert it into a rst article with your contribution.