When I worked for Lotus EI as an SE it took me about 2+ hours to answer the question you have asked, so I'll try to do my best while keeping this brief. First, let's start with the programmatic options - LS:DO, LC LSX, LC Java, Lotus Connector Toolkit and ADO. LC Java no longer exists, so... enough said. LS:DO is Lotus' original integration technology for ODBC data sources and will be your slowest performer. ADO is Microsofts interface for ODBC, so if you are writing VB or want to use the COM interface within LotusScript this would work - but slowly. That leaves you with LC LSX, which is a very good LotusScript API for leveraging connectors - which you could write with the Connector Toolkit. Next, let's discuss tools - DECS and LEI. DECS is for real-time access only, so if you have a UI application that should effect data on a back-end system this is as good fit. LEI is most commonly used to move data from one systems to another, but also has real-time capabilities. ESB sits in the middle of DECS/LEI and the LC LSX, as it is a stand-alone server that executes LotusScript agents for both back-end and UI functionality. For more specifics on these tools I suggest you contact your local Lotus rep and get them to connect you with the appropriate people within Lotus' EI group.
This was first published in July 2002