Troubles with the info-types implementation pattern and with topic nesting in troubleshooting.dtd

Assuming that the spec allows DTDs to be configured so that nested topics won't be present, I have found a design flaw in the DTD implementation pattern for *-info-types. Consider this example from topic.mod:

<!ENTITY % topic.content
                       "((%title;),
                         (%titlealts;)?,
                         (%shortdesc; |
                          %abstract;)?,
                         (%prolog;)?,
                         (%body;)?,
                         (%related-links;)?,
                         (%topic-info-types;)*)"

>

The problem with this construct is that it will not allow %topic-info-types; to be set to empty. The presences of the comma, the parenthesis, and the * occurrence-operator mean that a valid element name must be furnished by the %topic-info-types; parameter entity or the DTD will fail to parse. To correct this, the definition for %topic-info-types; must include the comma, the parenthesis, and the occurrence operator. For example:

<!ENTITY % topic.content

                       "((%title;),

                         (%titlealts;)?,

                         (%shortdesc; |

                          %abstract;)?,

                         (%prolog;)?,

                         (%body;)?,

                         (%related-links;)?

                         %topic-info-types;)"

>

The parameter entity definition in topic.mod becomes necessarily ugly:

<!ENTITY % topic-info-types

                          ", (%info-types;)*"

>

As also does the one in topic.dtd:

<!ENTITY % topic-info-types

              ", (topic)*"

>

This flaw has existed throughout DITA 1.2 and lives on in DITA 1.3. It also suggests that few, if any, have tried to turn off topic nesting.

I discovered this while researching George Bina's question about the "topic" element being available at the end an embedded task topic in a troubleshooting topic. That flaw was caused by the fact that I had neglected to override the the task-info-types parameter entity in troubleshooting.dtd. Specifically, the following parameter entity needs to be added to the TOPIC NESTING OVERRIDE section in troubleshooting.dtd:

<!ENTITY % task-info-types

              "task"

>

Without that override, task.mod defaults the task-info-types value to %info-types; allowing topic to appear as nested topic at the end of task. Of course, my preference would be to set task-info-types to empty in troubleshooting.dtd. And, that's how I discovered that the DTDs won't parse with empty *-info-types.

At any rate, the fix for troubleshooting.dtd and the *-info-types problem need to go on the TC agenda soon.

Best Regards,

-- 

Bob Thomas
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