Creating a RIA Services Solution problem

hi,

I am following this article: http://msdn.microsoft.com/en-us/library/ee707376(v=vs.91).aspx  to create a RIA Services Solution ,it says:

To create the domain service

1.Right-click the server project, select Add and New Item.

2.In the list of categories, select Web and then select the Domain Service Class template.

3.Name the class CustomerDomainService.cs (or CustomerDomainService.vb).

but why can't I find Domain Service Class template? What's wrong.