Example DTD

A DTD for our recipe collections, recipes.dtd: 

<!ELEMENT collection (description,recipe*)>

<!ELEMENT description ANY>

<!ELEMENT recipe (title,ingredient*,preparation,comment?,nutrition)>

<!ELEMENT title (#PCDATA)>

<!ELEMENT ingredient (ingredient*,preparation)?>
<!ATTLIST ingredient name CDATA #REQUIRED
                     amount CDATA #IMPLIED
                     unit CDATA #IMPLIED>

<!ELEMENT preparation (step*)>

<!ELEMENT step (#PCDATA)>

<!ELEMENT comment (#PCDATA)>

<!ELEMENT nutrition EMPTY>
<!ATTLIST nutrition protein CDATA #REQUIRED
                    carbohydrates CDATA #REQUIRED
                    fat CDATA #REQUIRED
                    calories CDATA #REQUIRED
                    alcohol CDATA #IMPLIED>

By inserting: 

<!DOCTYPE collection SYSTEM "recipes.dtd">

in the headers of recipe collection documents, we state that they are intended to conform to recipes.dtd.

Alternatively, the DTD can be given locally with <!DOCTYPE collection [ ... ]>.

This grammatical description has some obvious shortcomings: