给定参考外部dtd文件，xml文件不报告错误

Question

I have written a dtd file to regulate a xml file, but when wrote something wrong according to definition in the dtd file, I found no any errors exported by Eclipse. I reviewed many times on both files but found no mistake by myself. Below are the 2 simple files. Could anybody help to figure out what I am missing or the reason why no error reported? Thanks in advance.

Here is the dtd file,

<?xml version="1.0" encoding="UTF-8"?>
<--!no classNo or one classNo at most, at least one teacher-->
<!DOCTYPE school [
    <!ELEMENT school (class)>
    <!ELEMENT class (classNo?,teacher+)>
    <!ElEMENT classNo (#PCDATA)> 
    <!ElEMENT teacher (#PCDATA)>
]>

Here is the xml file,

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE school SYSTEM "Teacher.dtd">

<school>
    <class>
        <classNo>Class 3</classNo>
        <teacher>Mary</teacher>
    </class>
</school>

If I add another classNo Element, no error reported. The xml file and dtd file are in the same package in Eclipse.

Answer 1

The DTD is ill-formed. The DOCTYPE declaration should only be in the XML document, not in the DTD. There are a couple of typos as well (lower-case "l" instead of upper-case "L"; --! in the comment should be !-- ).

The XML document validates against this DTD:

<!ELEMENT school (class)>
<!ELEMENT class (classNo?,teacher+)>
<!ELEMENT classNo (#PCDATA)> 
<!ELEMENT teacher (#PCDATA)>

You also have to make sure that validation is enabled in Eclipse of course (assuming that XML Editors and Tools is installed).