DTD - attributes with fixed default values

Question

Lets say I have a snippet of a DTD declaration like this.

<!ELEMENT book ANY>
<!ATTLIST book genre #FIXED "fantasy">

Note that the genre attribute was declared with a fixed default value of fantasy.

What exactly is the meaning of such a declaration? Two possible interpretations come to mind:

1. A document is not valid unless each book element contain a genre attribute with value fantasy.
2. A document is valid if each book element either contains a genre attribute with value fantasy or does not contain the genre attribute at all.

I did not find a definitive answer in the DTD specification, even though the second one seems more likely because of the following part:

Validity constraint: Fixed Attribute Default

If an attribute has a default value declared with the #FIXED keyword, instances of that attribute MUST match the default value.

Answer 1

Interpretation 2 is the correct one. Demonstration:

DTD (fixed.dtd)

<!ELEMENT root ANY>

<!ELEMENT book ANY>
<!ATTLIST book id ID #IMPLIED
               genre CDATA #FIXED "fantasy">

<!ELEMENT magazine ANY>
<!ATTLIST magazine id ID #IMPLIED>

XML 1

<!DOCTYPE root SYSTEM "fixed.dtd">
<root>
  <book id="ID01" genre="fantasy"/>
  <magazine id="ID02" />
</root>

xmllint output:

$ xmllint --postvalid fixed.xml
<?xml version="1.0"?>
<!DOCTYPE root SYSTEM "fixed.dtd">
<root>
  <book id="ID01" genre="fantasy"/>
  <magazine id="ID02"/>
</root>

XML 2

<!DOCTYPE root SYSTEM "fixed.dtd">
<root>
  <book id="ID01"/>
  <magazine id="ID02" />
</root>

xmllint output:

$ xmllint --postvalid fixed.xml
<?xml version="1.0"?>
<!DOCTYPE root SYSTEM "fixed.dtd">
<root>
  <book id="ID01"/>
  <magazine id="ID02"/>
</root>

XML 3

<!DOCTYPE root SYSTEM "fixed.dtd">
<root>
  <book id="ID01" genre="crime"/>
  <magazine id="ID02" />
</root>

xmllint output:

$ xmllint --postvalid fixed.xml
<?xml version="1.0"?>
<!DOCTYPE root SYSTEM "fixed.dtd">
<root>
  <book id="ID01" genre="crime"/>
  <magazine id="ID02"/>
</root>
fixed.xml:3: element book: validity error : Value for attribute genre of book is different from default "fantasy"
fixed.xml:3: element book: validity error : Value for attribute genre of book must be "fantasy"
Document fixed.xml does not validate

Answer 2

The second one is true! In effect the attribute can not declarate in XML.