What is it?
A data-source is a set of model element used to create synctables. To create a primary data-source, you should use the following syntax:
'data-source' name('*')? Qualifier 
What does the * do?
The asterisk will trigger some MapleMBSE internal logic to construct at loading or reloading time a read only set with all the elements filtered using the Qualifier. For example:
data-source blocks* [Class|mse::metaclassName = “SysML::Blocks::Block”]
This configuration will create a data-source called blocks containing the entire block in the resource set.
Are the regular primary data-sources and the all primary data-sources interchangeable?
Not completely. The all primary data-sources do not guarantee bijection and creating an element in Excel using an all primary data-source may be problematic. There would be no problem if you create a synctable to join internally in the configuration file.
Caution: If you allow an end user to see a sync view with an all primary data-source, they might be able to rename and delete elements.
Why don’t I see my newly created elements if I show an all primary data-source?
As explained before, this feature is read only and is created on loading or reloading time. This means that any changes in other tables that impact all primary data-source syncviews would only show after loading or reloading.
 For further information, see the MapleMBSE Configuration Guide: https://www.maplesoft.com/documentation_center/maplembse2019/MapleMBSEConfigGuide.pdf