I am writing a GIS app that allows import of various file formats, and I want to include an importer for data coming out of ArcGIS. My understanding was that Geodatabase was the default format for sharing ArcGIS data, and I am familiar with the C++ SDK API they provide for reading Geodatabase.

I asked this question:

Does Esri Geodatabase contain style information?

and learned that a Geodatabase itself does not contain styling information.

But if Geodatabase doesn't contain style info, it made me wonder how ArcMap users share data with each other when they want to include styling information.

I learned that styling information for an Esri map can be found (along with the geometry data) in a Layer Package or a Map Package.

So I am now trying to understand if there is a documented way for me to read the style information from a Layer Package or Map Package. But even if there were, I don't know if there is a way for me (as an app external to ArcMap) to read the geometry out of a Layer Package or Map Package. (I don't know, for instance, if Layer and Map packages include a Geodatabase as a subset of their data, and I could read that Geodatabase using the API SDK.)