Question

How would I know if The XML that I created follows the rule that is in my DTD?

here’s my XML

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE HW SYSTEM "HW.dtd">
<A>
    AA = "BAR"
    AB = "FOO"
    AC = "1"
    <C>
        <B/>
        CA = "Name"
    </C>
    <D>Element</D>
</A>

and here is my DTD

<?xml version="1.0" encoding="ISO-8859-1"?>
<!ELEMENT A (B* |C+,D)>
<ATTLIST A
    AA CDATA #REQUIRED
    AB CDATA #REQUIRED
    AC(0|1|2) #REQUIRED
>
<!ELEMENT B EMPTY>
<!ATTLIST C(B)>
<!ATTLIST C
    CA CDATA #REQUIRED
>
<!ELEMENT D (#PCDATA)>

is my XML correct with the DTD?

Answer 1

You need to Use an XML Validator,

An Online version is http://www.xmlvalidation.com/, there are lots of tools that do this also

According to the validator, your DTD is not valid

I’ve tried to fix up your DTD, here’s the fixed up version

<?xml version="1.0" encoding="ISO-8859-1"?>
<!ELEMENT A (B* | (C+,D))>
<!ATTLIST A
    AA CDATA #REQUIRED
    AB CDATA #REQUIRED
    AC (0|1|2) #REQUIRED
>
<!ELEMENT B EMPTY>
<!ELEMENT C EMPTY>
<!ATTLIST C
    CA CDATA #REQUIRED
>
<!ELEMENT D (#PCDATA)>

The problems with the DTD you posted were:

As far as I could see you need the brackets around C+,D also the <ATTLIST above is incorrect as you specify a list of attributes with <!ATTLIST note the ! was missing.

Also your DTD had

<!ELEMENT B EMPTY>
<!ATTLIST C
    CA CDATA #REQUIRED
>

Which failed validation as you were defining an attribute list from element C <!ATTLIST C but hadn’t defined the Element C in the DTD, therefore I changed it to

<!ELEMENT C EMPTY>
<!ATTLIST C
    CA CDATA #REQUIRED
>

This makes your DTD valid

Also your XML is wrong in quite a few ways

for example your DTD specifices

<!ATTLIST A
    AA CDATA #REQUIRED
    AB CDATA #REQUIRED
    AC (0|1|2) #REQUIRED
>

Which means that Element A must have the attributes AA BB AC as they are required also AC attribute must be 0 or 1 or 2

You have put

<A>
    AA = "BAR"
    AB = "FOO"
    AC = "1"

Which is not specifiying XML attributes in the Element A, to specify attributes it should be

<A AA="BAR" AB="FOO" AC="1">

This should help you do your homework

heres a link http://www.quackit.com/xml/tutorial/dtd_introduction.cfm to a DTD tutorial this should help you create an XML doc that validates against it