You can connect in two ways, through ODBC or the Business Object Interface (BOI) that is scripting.  What does your application do.

We're an analytics and business intelligence solution, I was trying to get the documentation for our developer to build the integration, is there not a way to connect if we built the integration to an open API for Sage 100 2019 desktop version? They're currently on the 2017 API but upgrading to the 2019 version-- any help or guidance would be appreciated :) 

If your integration works on Sage 100 v2017, if that is what you are saying, then it will work on the v2019 version.

If you take the BOI class in Sage U you will receive the documentation

@biglouie thanks for being so helpful! Is the BOI class in Sage U free? Is there a link to sign up for it!? Thank you again for all your help!!! 

Not free, click on the link at the top of this forum that says "training"

Awesome, I clicked on training but am not seeing the BOI class, do you know a ballpark of what the class costs?

Megan... 
See the link below.

https://sageu.csod.com/LMS/LoDetails/DetailsLo.aspx?loid=9cadd213-40cb-4b16-ac4c-5d741c9b61ee&query=%23q%3D%26s%3D1%26a%3Dtyp%253d0%2526sub%253d806&back_key=1#t=1