Question

please pardon me if this is too simple question, since I am just a beginner in this field.

My client used to work with a dtd, called “article.dtd” for a long time. Now they decided to extend that dtd a little bit, with some more elements and rename it as “project.dtd”. Since the new elements added to the article.dtd is of just a few lines, they don’t want to copy everything from article.dtd everytime they create project.dtd.

Thus, I am seeking a way, if it is possible to reference article.dtd from newly-created project.dtd, and in project.dtd, we only need to put in those lines that are not contained in article.dtd?

FYI, these are the four lines that are added in project.dtd:

<!ELEMENT project (title, keywords?, feature?, related-terms?, abstract?, classification?, contributor*, reviewer?, materials?, body, related-links?, questions?)>     
<!ATTLIST project %common-atts; %status-atts; %profile-atts;> 

<!ELEMENT abstract ((%para-elems;)+)>
<!ATTLIST abstract %common-atts;>

Thanks for the help in advance.

Answer 1

Yes, you can do this with a parameter entity. (It looks like you’re using a lot of parameter entities already.)

You will need to add a parameter entity declaration (<!ENTITY % entity-name ...>) and a parameter entity reference (%entity-name;).

Here’s an example using the entity name article-dtd. This would be your complete project.dtd:

<!ENTITY % article-dtd SYSTEM "article.dtd">
%article-dtd;

<!ELEMENT project (title, keywords?, feature?, related-terms?, abstract?, classification?, contributor*, reviewer?, materials?, body, related-links?, questions?)>     
<!ATTLIST project %common-atts; %status-atts; %profile-atts;> 

<!ELEMENT abstract ((%para-elems;)+)>
<!ATTLIST abstract %common-atts;>

I only used a SYSTEM identifier in the entity declaration, but you can add a PUBLIC identifier too.

Example:

<!ENTITY % article-dtd PUBLIC "-//SO//Stackoverflow Test//EN" "article.dtd">