In the previous section we discussed an example of transforming an XML schema into XNF. We started with the schema [S.sub.1] in Figure l, and the final schema was [S.sub.4] in Figure 9.
the XNF is restricted to the subtree determined by this context path.
But then the absolute XNF for [S.sub.1] cannot be achieved.
In this section we will discuss how to transform an ER (Entity-Relationship) schema  into XML schema in XML normal form (XNF).
Satisfaction of this condition is the prerequisite to obtain an XML schema in absolute XNF in the next step.
The DA algorithm  is applied to obtain the final XNF schema.
Now, using the Theorem 7.3 and DA, the transformation of ER into XNF is realized in the following two steps:
db [right arrow] supplier * partDese * supplier [right arrow] sid sname part * partDesc [right arrow] pid pname part [right arrow] pid did offer * offer [right arrow] oid price delivTime (3) Applying the above steps to the ER schema from Figure 12 gives the XML schema in XNF depicted in Figure 15 and its instance in Figure 16.