EDIT
I am having trouble implementing a DTD. I keep getting an error in my DTD saying:
"The markup in the document preceding the root element must be well-formed."
In my XML document I get the error:
"The markup declarations contained or pointed to by the document type declaration must be well-formed."
DTD
<?xml version="1.0" encoding="UTF-8"?>
<!-- New document created with EditiX at Sun Jul 06 07:25:48 AST 2014 -->
<!ELEMENT periodic-elements (periodic-element*)>
<!ELEMENT periodic-element (symbol, name, atomic-number, atomic_weight)>
<!ELEMENT symbol (#PCDATA)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT atomic_number (#PCDATA)>
<!ELEMENT atomic_weight (#PCDATA)>
XML
<?xml version="1.0" encoding="UTF-8"?>
<!-- New document created with EditiX at Sun Jul 06 07:25:48 AST 2014 -->
<!DOCTYPE periodic SYSTEM "C:\Users\Randy\Desktop\CMIS 170\Week 3\Homework 3\Homework3DTD.txt">
<periodic>
<element>
<symbol>FE</symbol>
<name>Iron</name>
<atomic_number>26</atomic_number>
<atomic_weight>55.845</atomic_weight>
</element>
<element>
<symbol>Ir</symbol>
<name>Iridium</name>
<atomic_number>77</atomic_number>
<atomic_weight>192.217</atomic_weight>
</element>
<element>
<symbol>P</symbol>
<name>Phosphorus</name>
<atomic_number>15</atomic_number>
<atomic_weight>30.973762</atomic_weight>
</element>
<element>
<symbol>Uut</symbol>
<name>Ununtrium</name>
<atomic_number>113</atomic_number>
<atomic_weight>284</atomic_weight>
</element>
<element>
<symbol>Po</symbol>
<name>Polonium</name>
<atomic_number>84</atomic_number>
<atomic_weight>209</atomic_weight>
</element>
</periodic>
Any help would be appreciated.