if I understand your code example, you try to add a new sub-tree (of type detail) to your document (myProduct). You could do this with the following line of code
// – index, where to insert the detail node into the list of details. int idx = ???; // – insert, a new node of type detail to the element product. BusinessNode detail = myProduct.getDescendant(“/product”).insert(idx, “detail”); // – set the values of detail: // (a) u3e getDescendant(…) for getting sub-nodes of d