Unfortunately you cannot call a web service returning a dataset in Biztalk 2004 with the SOAP adapter. This limitation applies to any array
This has something to do with BPEL.
One possible workaround if you can change the Web Service is to use a container object
[code:1:a48a3610dc]public class DSContainer
{
DataSet myDataSet;
}
[WebMethod]
public DSContainer getDataset()[/code:1:a48a3610dc]
Another work around is to use the WSE adapter
Apparently Biztalk 2006 is capable of handling a Web Service returning a DataSet, although I have yet to try this.