To give a topic an ID, do one of the following:
In the absence of either marker, the default topic ID is the base file name, adjusted as for CSS class names; see §24.8.4 Adjusting DITA topic IDs generated from file names.
If you do not insert markers for topic IDs, DITA2Go makes up an ID for each embedded topic after the first (which uses the base file name). These generated IDs are of the form topic2, topic3, and so forth. This is not recommended practice.
To specify a default ID other than the base file name (but only for the first topic in a file), include the following option in your project configuration file:
[DITAOptions] ; TopicID = id for topic, default is base file name TopicID = someid
You can override the default ID with a DITATopicID PI marker, or with a FileName PI marker.