XML和DTD中的ID和IDREF配置

Question

This is my first attempt at XML and I'm not able to validate the xml at all. The DTD gets validated, but not the XML. I'm not able to figure out the ID and IDREF part. Can someone tell me how I can fix this as I keep getting the error "Element type must be declared" particularly for medID and docID when I try to validate.

Here's the XML

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE patient_list SYSTEM "patients.dtd">
<patient_list>
<patient serialNo="a1b2c3">
<patientFName>Jon</patientFName>
<patientLName>Won</patientLName>
<gender>male</gender>
<medID IDREF="M1"/>
<docID IDREF="D37"/>
</patient>

<patient serialNo="k4t5g2">
<patientFName>Min</patientFName>
<patientLName>Hin</patientLName>
<gender>female</gender>
<medID IDREF="M2"/>
<docID IDREF="D21"/>
</patient>

<medicine medID="M1">
<name>Panadol</name>
<manufacture>GSK</manufacture>
<regNo>oo9807</regNo>
</medicine>

<medicine medID="M2">
<name>Alprazolam</name>
<manufacture>Novartis</manufacture>
<regNo>hu5432</regNo>
</medicine>

<doctor docID="D21">
<registration ID="8472392"/>
<fName>Alfred</fName>
<lName>Campbell</lName>
<specialisation>Paediatrics</specialisation>
</doctor>

<doctor docID="D37">
<registration ID="4364786"/>
<fName>Mick</fName>
<lName>Foley</lName>
<specialisation>Psychiatry</specialisation>
</doctor>
</patient_list>

and here's the DTD:

<!ELEMENT patient_list (patient+, medicine+, doctor+)>
<!ELEMENT patient (patientFName, patientLName, gender)>
<!ATTLIST patient serialNo CDATA #REQUIRED>
<!ELEMENT patientFName (#PCDATA)>
<!ELEMENT patientLName (#PCDATA)>
<!ELEMENT gender (#PCDATA)>

<!ATTLIST medicine medID ID #REQUIRED>
<!ATTLIST doctor docID ID #REQUIRED>

<!ELEMENT medicine (name, manufacture, regNo)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT manufacture (#PCDATA)>
<!ELEMENT regNo (#PCDATA)>

<!ELEMENT doctor (registration, fName, lName, specialisation)>
<!ELEMENT registration (#PCDATA)>
<!ATTLIST registration ID CDATA #REQUIRED>
<!ELEMENT fName (#PCDATA)>
<!ELEMENT lName (#PCDATA)>
<!ELEMENT specialisation (#PCDATA)>

Answer 1

I think the attributes medID on medicine and docID on doctor are fine. They're both declared as the attribute type ID like they should be.

I think where your problem is happening is when you try to use medID and docID as elements without declaring them. Instead of using the same name as the medID and docID attributes, name them something different like medref and docref .

The attribute IDREF would need to be declared too, however IDREF is another attribute type so you should name the attribute something else like refid .

Full example...

XML

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE patient_list SYSTEM "patients.dtd">
<patient_list>
    <patient serialNo="a1b2c3">
        <patientFName>Jon</patientFName>
        <patientLName>Won</patientLName>
        <gender>male</gender>
        <medref refid="M1"/>
        <docref refid="D37"/>
    </patient>

    <patient serialNo="k4t5g2">
        <patientFName>Min</patientFName>
        <patientLName>Hin</patientLName>
        <gender>female</gender>
        <medref refid="M2"/>
        <docref refid="D21"/>
    </patient>

    <medicine medID="M1">
        <name>Panadol</name>
        <manufacture>GSK</manufacture>
        <regNo>oo9807</regNo>
    </medicine>

    <medicine medID="M2">
        <name>Alprazolam</name>
        <manufacture>Novartis</manufacture>
        <regNo>hu5432</regNo>
    </medicine>

    <doctor docID="D21">
        <registration ID="8472392"/>
        <fName>Alfred</fName>
        <lName>Campbell</lName>
        <specialisation>Paediatrics</specialisation>
    </doctor>

    <doctor docID="D37">
        <registration ID="4364786"/>
        <fName>Mick</fName>
        <lName>Foley</lName>
        <specialisation>Psychiatry</specialisation>
    </doctor>
</patient_list>

DTD

<!ELEMENT patient_list (patient+, medicine+, doctor+)>
<!ELEMENT patient (patientFName, patientLName, gender, medref*, docref*)>
<!ATTLIST patient serialNo CDATA #REQUIRED>
<!ELEMENT patientFName (#PCDATA)>
<!ELEMENT patientLName (#PCDATA)>
<!ELEMENT gender (#PCDATA)>

<!ATTLIST medicine medID ID #REQUIRED>
<!ATTLIST doctor docID ID #REQUIRED>

<!ELEMENT medref EMPTY>
<!ATTLIST medref refid IDREF #REQUIRED>

<!ELEMENT docref EMPTY>
<!ATTLIST docref refid IDREF #REQUIRED>

<!ELEMENT medicine (name, manufacture, regNo)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT manufacture (#PCDATA)>
<!ELEMENT regNo (#PCDATA)>

<!ELEMENT doctor (registration, fName, lName, specialisation)>
<!ELEMENT registration (#PCDATA)>
<!ATTLIST registration ID CDATA #REQUIRED>
<!ELEMENT fName (#PCDATA)>
<!ELEMENT lName (#PCDATA)>
<!ELEMENT specialisation (#PCDATA)>