Data connectivity to third party applications

I often get this query from my sales: "How can I connect to this xyz application" which falls into the long-tail of connectivity problem. There are multiple ways of connecting to third party applications which may fall into any of the following categories:

1.  Standard 2-tier or 3-tier application: Majority of the custom business application deployed at an enterprise customer site would have a database behind the application. Typically, connecting directly to the database using either our native or ODBC drivers would be the easiest data  integration point for such a custom application which does not expose any other standard application interfaces.
2.      Cloud hosted application: Many of the new cloud based application vendors provide the standard Web-Services/REST based interface for connecting to the application
3. On-premise or cloud application exposing CLI’s to integrate: Use standard CLI functions that are exposed by the applications and write a custom program to integrate with the flat files generated as the output of the CLI 
4. No DB Connection, No Webservices or CLI interface - Exposed through programming API: If none of the above is possible and the third party applications needs to build an exclusive connection using a programming API(C,C++,Java) to the connecting applications.

In addition to the base connectivity decision areas as mentioned above, we would need to look at the customer’s data integration use cases for connecting into each of the following areas before defining the appropriate connectivity solution.

      a)      Volume of data & Scalability (partitioning, Bulk interfaces, CDC etc)

      b)      Velocity (performance-bulk or real time)

      c)       Security(authentication, authorizations, data staging concerns etc)

      d)      Variety(mapping application data types to your data types or transforming the specialized encoded data such as JSON, EDIFACT)  

       e)      Validity (history snapshots or real time)