How does SharePoint render a page?

Question

This is a noob question... I am trying to understand how site definitions, templates, etc. all work together when a SharePoint page is requested. I understand that site definitions are "base templates" while site templates capture the "delta" between site definitions and applied customizations.

When a page request is received by SharePoint, how does SharePoint know which base site definition to use? I looked at the Web table (in the content DB) and see a WebTemplate column. I was able to map that back to the templates defined in WebTemplate XML files located at C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\1033\XML\WebTemp*.xml. Does each Template in these files correspond to a folder under ....\SiteTemplates\?

With customization, use of custom site templates (STP files) and pages getting unghosted (or customized), I have heard that the pages or templates themselves are stored in the database as opposed to using those on the WFE server.

I could not find any one explanation or article that paints the whole picture!

Answer 1

The Site Definitions are not examined when rendering a page but during provisioning.

For a detailed explanation of the rendering see the link provided by @Moss Farmer, but let me give a shorter version here.

Application pages (from _layouts)
Application pages are just ordinary ASP.NET pages which are rendered from a virtual directory.

Site pages
The site pages are a bit more complicated, but the basic is that for each there is a record in the content database (AllDocs) with a column (SetupPath) specifying where in the SharePointRoot the original page is stored and a bit (HasStream) specifing if the page has been customized (unghosted). If the page is uncustomized (ghosted) it's rendered from the SharePointRoot file.
If the page is customized (unghosted) the content is found in another table (AllDocStreams) in the content database and rendered from here.

Provisioning
The Site definitions/Site Templates/Web Templates/Features are all things which is used when you create the Site collection/Site to provision the pages (amonst other things)

Answer 2

Speaking of page rendering process its pretty much the same with 2007 and 2010. Please read this lengthy 2 part architectural series of SharePoint by Microsoft that explains in depth of how a requested page is rendered by SharePoint.

http://msdn.microsoft.com/en-us/library/bb892189(v=office.12).aspx

This should "almost" answer the basic questions you have above.

Answer 3

The article suggested by Moss Farmer explains how SharePoint sits on top of ASP.NET Framework and IIS and also explains general SharePoint page processing. It will also explain the difference between rendering of ghosted and unghosted page.

As far as Site Definition and Site Templates, they have nothing to do with Rendering of page. Site Definitions and Site Templates are just provisioning framework. When you use them, SharePoint provisions different artifacts in the site. Think of them as a way to describe what should the site consists of and which functionality should be enabled when you create a site using a particular site definition. This is one-time operation which basically sets up the site as per the need. For example, Publishing Site Definition will create a site, create libraries like Pages, Reusable Content, Style Library, Put some page layouts in master page gallery, create a page in Pages library, enable publishing workflow template and publishing feature, create a sub site, installs master pages in master page gallery and sets one of the master page as default master page etc. All that share point does is execute the content of XML definition and performs actions like above.