How to: Programmatically Modify Site-Map Nodes in Memory.

Question

I have XML file and and I would like to site map filled from this XML file. How is it possible?

<siteMap>
<siteMapNode title="Home" description="Home" url="~/default.aspx">
<siteMapNode title="Products" description="Our products"
  url="~/Products.aspx">
  <siteMapNode title="Hardware" description="Hardware choices"
    url="~/Hardware.aspx" />
  <siteMapNode title="Software" description="Software choices"
    url="~/Software.aspx" />
</siteMapNode>
<siteMapNode title="Services" description="Services we offer"
    url="~/Services.aspx">
    <siteMapNode title="Training" description="Training classes"
      url="~/Training.aspx" />
    <siteMapNode title="Consulting" description="Consulting services" 
      url="~/Consulting.aspx" />
    <siteMapNode title="Support" description="Supports plans" 
      url="~/Support.aspx" />
</siteMapNode>
</siteMapNode>
</siteMap>