XML - How Can I Add a Second Entry?

Question

I want to try and add a second entry to my XML file, however, upon adding another entry I get an error on the validator

Code: Here is my DTD:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<!DOCTYPE car [

    <!ELEMENT car (make, model, year, colour, engine, accessories)>

    <!ELEMENT make (#PCDATA)>
    <!ELEMENT model (#PCDATA)>
    <!ELEMENT year (#PCDATA)>
    <!ELEMENT colour (#PCDATA)>
    <!ELEMENT engine (number_of_cylinders, fuel_system)>
    <!ELEMENT number_of_cylinders (#PCDATA)>
    <!ELEMENT fuel_system (#PCDATA|carburetted|fueld-injected)*>
    <!ELEMENT accessories EMPTY>
        <!ATTLIST accessories radio (yes|no) #REQUIRED>
        <!ATTLIST accessories air_conditioning (yes|no) #REQUIRED>
        <!ATTLIST accessories power_steering (yes|no) #REQUIRED>
]>

XML Entry:

<car>
    <make>Ford</make>
    <model>001</model>
    <year>2014</year>
    <colour>black</colour>
    <engine> <number_of_cylinders>3</number_of_cylinders> <fuel_system>"carburetted"</fuel_system></engine>
    <accessories radio="yes" air_conditioning="yes" power_steering="yes"/>
</car>

Answer 1

You're only allowed to have one root element, so you're going to need to add another element that can contain multiple car elements.

Something like:

<!ELEMENT cars (car+)>

I noticed a couple of other things too.

1. It seems like you're confusing internal and external subsets. You're not allowed to have a doctype declaration in an external subset. In the example you gave that should all be one file. If the DTD is in a separate file, move the doctype declaration from the DTD to the XML instance and reference the DTD.

2. You can simplify your attribute declarations by only using 1 per element.

3. You reference the elements carburetted and fueld-injected, but don't declare them. It looks like you actually want the option of 2 values. You can't do that with DTD so you'll have to make an attribute with the enumerations.

Here are a couple of examples that show:

• the internal subset
• the external subset
• the extra element references converted to type attribute
• the attribute declaration simplification
• the addition of the cars element

Internal Subset Example

cars.xml

<!DOCTYPE cars [

<!ELEMENT cars (car+)>

<!ELEMENT car (make, model, year, colour, engine, accessories)>

<!ELEMENT make (#PCDATA)>
<!ELEMENT model (#PCDATA)>
<!ELEMENT year (#PCDATA)>
<!ELEMENT colour (#PCDATA)>
<!ELEMENT engine (number_of_cylinders, fuel_system)>
<!ELEMENT number_of_cylinders (#PCDATA)>
<!ELEMENT fuel_system EMPTY>
<!ATTLIST fuel_system
          type (carburetted|fuel-injected) #REQUIRED>
<!ELEMENT accessories EMPTY>
<!ATTLIST accessories 
          radio            (yes|no) #REQUIRED
          air_conditioning (yes|no) #REQUIRED
          power_steering   (yes|no) #REQUIRED>
]>
<cars>
    <car>
        <make>Ford</make>
        <model>001</model>
        <year>2014</year>
        <colour>black</colour>
        <engine> 
            <number_of_cylinders>3</number_of_cylinders> 
            <fuel_system type="carburetted"/>
        </engine>
        <accessories radio="yes" air_conditioning="yes" power_steering="yes"/>
    </car>
</cars>

External Subset Example

cars.dtd

<!ELEMENT cars (car+)>

<!ELEMENT car (make, model, year, colour, engine, accessories)>

<!ELEMENT make (#PCDATA)>
<!ELEMENT model (#PCDATA)>
<!ELEMENT year (#PCDATA)>
<!ELEMENT colour (#PCDATA)>
<!ELEMENT engine (number_of_cylinders, fuel_system)>
<!ELEMENT number_of_cylinders (#PCDATA)>
<!ELEMENT fuel_system EMPTY>
<!ATTLIST fuel_system
          type (carburetted|fuel-injected) #REQUIRED>
<!ELEMENT accessories EMPTY>
<!ATTLIST accessories 
          radio            (yes|no) #REQUIRED
          air_conditioning (yes|no) #REQUIRED
          power_steering   (yes|no) #REQUIRED>

cars.xml

<!DOCTYPE cars SYSTEM "cars.dtd">
<cars>
    <car>
        <make>Ford</make>
        <model>001</model>
        <year>2014</year>
        <colour>black</colour>
        <engine> 
            <number_of_cylinders>3</number_of_cylinders> 
            <fuel_system type="carburetted"/>
        </engine>
        <accessories radio="yes" air_conditioning="yes" power_steering="yes"/>
    </car>
</cars>