Missing Schema Info

Question

I am getting this error message n Visual Studio: "Could not find Schema Information Number, Name, Period, a0 and aJ." I have a working schema "SemiMajorAxis.xsd" but I do not know how to use it. Later in the program I deal with the DataTable

SemiMajorAxis.aspx.cs

       DataSet dsread = new DataSet();
       DataTable dtread = new DataTable();
       dsread.ReadXml(Server.MapPath("SemiMajorAxis.xml"));
       dtread = dsread.Tables[0];
       
       XDocument xmldoc = XDocument.Load(Server.MapPath("SemiMajorAxis.xml"));
       var elements = from data in xmldoc.Descendants("planet")
           select new
           {
               Numberp = (int)data.Element("Number"),
               Namep = (string)data.Element("Name"),
               Pyrsp = (double)data.Element("Period"),
               a0p = (double)data.Element("a0"),
               aJp = (double)data.Element("aJ")
           };

       foreach (var element in elements)
       {
           m = m + 1;
           num[m] = element.Numberp;
           name[m] = element.Namep;
           a0[m] = element.a0p;
           aJ[m] = element.aJp;
           a[m] = a0[m] + aJ[m] * J;
       }

SemiMajorAxis.xml

   <?xml version="1.0" standalone="yes"?>
     <planets>
        <planet>
           <Number>1</Number>
           <Name>Mercury</Name>
           <Period>0.2408</Period>
           <a0>0.38709893</a0>
           <aJ>0.00000066</aJ>
        </planet>
        <planet>
           <Number>2</Number>
           <Name>Venus</Name>
           <Period>0.6152</Period>
           <a0>0.72333199</a0>
           <aJ>0.00000092</aJ>
        </planet>
        <planet>
           <Number>3</Number>
           <Name>Earth</Name>
           <Period>1</Period>
           <a0>1.00000011</a0>
           <aJ>-0.00000005</aJ>
        </planet>
     </planets>