A site definition defines unique type of Sharepoint site. There are five site definition natively installed in WSS. A site definition can inculde more than one site definition configuration. Sharepoint web site are based on particular site definition configurations.
- STS incudles the site definition configurations for team site, blank site, and document workspace.
- MPS includes the site definition configurations for basic meeting workspace, blank meeting workspace, decision meeting workspace, social meeting workspace, and multiple meeting workspace.
- CENTRALADMIN provides a site definition configuration for central administration web sites
- Wiki provides a site definition configuration for web sites that support community content using wiki technology
- BLOG provides a site definition configuration for blogs.
Site definition files are cached in memory on the server at process startup of Microsoft Internet Information Services (IIS), which improves scalability and performance by reducing unnecessary data storage or retrieval, and by allowing uncustomized pages to be reused across sites. The information contained in these files is pulled from the cache at run time. Pages and list schemas are read from the site definition files but appear to be actual files within a site, which is why these files are referred to as "ghosted." Ghosted pages are therefore pages whose actual content does not reside in the database but on disk. A row for each page is in the database and it contains a column value that points to the source for the page in the file system. New Web Part pages are also ghosted.
When site pages are customized, excluding browser-based customizations such as modifications to Web Parts, the pages become "unghosted" and their contents are stored in the database. Uploaded .aspx files are considered unghosted automatically. The contents of unghosted pages are routed through safe mode parsing in ASP.NET, which prevents server-side code from executing, and which depends entirely on the Safe Controls list — specified in the web.config file of the Windows SharePoint Services application's subfolder in C:\Inetpub\wwwroot\wss\VirtualDirectories — to determine which controls can be rendered at run time.
Core Schema files
Defines the navigation areas, specifies the list definitions available on the Create page, specifies document templates and their files, defines the base types for lists, and defines configurations and modules for site. The folder is definitions.\TEMPLATE\SiteTemplates\ site_type \XML . There may be other files and folders in the xml folder. For example, default.aspx, lists folder , dwp folder
Defines the views, forms, toolbar, and special fields in a list definition. Each definition has its own Schema.xml file. They are in folder \TEMPLATE\FEATURES\List_Definition_Name
Identifies the site definitions and provides information about how their configurations will appear in the template selection section of the New Sharepoint site page. The folder is "\Template\1033\xml".
Maps the file ProgIDs and file extensions of document types to specific for opening each type.