If your source is not DocBook, it is likely to be structurally similar to DocBook. The only mapping that I know of from DocBook to DITA is to express the the DocBook structure as nested topics, preferably through DITA maps. As you imply, DocBook's section element, or its concrete versions (sect1 through sect5), will not map to the DITA section element. Instead, DocBook sections must map to DITA topics with the expectation that the DITA topics will be nested.

Here is one way that you could proceed with a conversion:

1. Convert a DocBook instance into a monolithic DITA instance that parses against the Composite DTD (ditabase.dtd). Map all chapters, sections, and appendixes to DITA topics using topic nesting.
2. Prepare to factor the monolithic DITA instance into individual topics by setting the otherprops attribute on each topic to the target topic type. For each topic you would indicate whether it is to become a concept, reference, task, or remain as topic. You may be able to programmatically do some of this work as part of step 1.
3. Indicate which topics will become DITA maps by setting their outputclass to "map".
4. Convert the monolithic instance into DITA maps and topics based on the attribute settings from steps 2 and 3. Be sure to disgard the otherprops and outputclass values when creating the topics.

If your existing documentation is like most, your will have several topics that are not written according to information type. In step 2, I would leave topics that require rewriting as topic rather than forcing them into concept, reference, or task. The expectation is that authors would refactor this information into one or more information typed-topic. Rewriting content can potentially take much more time than all of the programming and tagging implied in the above steps. It may be tempting to avoid the rewriting, but the rewriting is absolutely necessary to unlock all of DITA's potential.

Regards,

Bob Thomas

Tagsmiths, LLC