Per the Web Services install/Admin guide:
>Web Services for Microsoft Dynamics GP is constructed on a base of Windows
Communication Foundation (WCF) and eConnect. (There is an illustration in the install guide)
>The Dynamics GP web service uses eConnect to provide access to the data managed
by the accounting system. eConnect is a set of SQL stored procedures and
supporting code used by integrating applications to access data in Microsoft
Dynamics GP. Data validation logic is built into eConnect, helping ensure the
integrity of any data written to the database through the web services.
The eConnect interfaces can still be used when the Dynamics GP web service is
installed. This allows you to run integrations based directly on eConnect on the
same installation as the Dynamics GP web service.
Thanks