Design XML DTD file and XML document file for the following relational schema:

Customer(cname, cresidence, ctel)

Item( item_name, item_code)

Order_request( customer, set_of_product)

Ctel can be a residence number or a mobile number.

order_file.dtd XML DTD

<! DOCTYPE order_request [
<!ELEMENT order_request(customer,item*)>
<!ELEMENT customer(cname,cresidence,ctel)>
<!ELEMENT cname(#PCDATA)>
<!ELEMENT cresidence(#PCDATA)>
<!ELEMENT ctel(residence| mobile)>
<!ELEMENT residence(#PCDATA)>
<!ELEMENT mobile(#PCDATA)>
<!ELEMENT item(item_name,item_code)>
<!ELEMENT item_name(#PCDATA)>
<!ELEMENT item_code(#PCDATA)>
]>

Order_request.xml
<?xml version=”1.0” standalone=”no”?>
<!DOCTYPE orderrequest SYSTEM “order_file.dtd”>
<order_request>
    <customer>
        <cname> Jack</cname>
        <cresidence> JAPAN </cresidence>
        <ctel>
            <residence> 022-23456789</residence>
            </ctel>
    </customer>
    <item> …