biztalk - What could be wrong with this xsd? -

I have an xsd when I try to validate it in BizTalk, these errors:

  Error BEC2009: The node "schema"; - The schema reference "http://www.w3.org/2001/xml.xsd" is not a valid reference or is not present in the current project. Error BEC2009: The node "schema"; - The schema reference "http://www.w3.org/2001/xml.xsd" is not a valid reference or is not present in the current project. Warning BEC999: 'schema location' attribute can not be resolved Error BEC3001: 'http://www.w3.org/XML/1998/namespace:space' attribute has not been declared. Warning BEC999: 'schema location' attribute can not be resolved Warning BEC1007: The node "schema"; - The target namespace is empty  

I think this is talking about namespace that looks like this:

To ensure that there is enough information to go to it ...

EDIT:
I came to know which program I agree with XML sometimes works for example. If I make some pure code to validate an XML against the schema then it reads xsd fine and validates XML if i use XML validation in Notepad ++, then it says that although this schema Can not read. In another mapter (WTX) they say that it also does not work.

Are there other things that I can try to reduce potential issues?

Edit 2:
Thanks xcut. I found that if I download the schema locally and keep it in the BizTalk project, then the schema is valid, but with 1 warning: Warning BEC1007: Node "" - The target namespace is empty.

Also it is strange to import the namespace schema, it may be that BizTalk simply Can not import a schema through the URL (while your net code can).

To exclude this as an issue, download the schema from w3.org, insert it into your project and click on http.