A common schema related error that may occur when building BizTalk projects that include schemas is:
BEC2017: Node "<Schema>" - This schema file has a TypeName that collides with the RootNode TypeName of one of its root nodes. Make sure that they are different.
The reason for this is quite simple - when the project is compiled, a .NET class will be generated for each top level element in your schema. If you have two schemas which share the same top level element name a clash will occur.
This is quite a common scenario and it is not always practical (or even possible) to change the element names. The solution is to change the generated type name for the schema. To do so, select the schema in the Solution Explorer and press F4 to display the Properties window. Then change the Type Name property so that it is not the same as any of the top level elements.