If you are an ISV and you create an application that connects against SAP (for example a mobile solution), you always have to consider the following things:

• Do you interface with SAP via a way, that is future proof? That can be either standard BAPIs or WebServices. Of course it also includes the possibility to create your own function modules or WebServices, but on the inside you can also only use standard functionality, for which SAP guaranties that it will be available in future releases. Just using some function modules that you discovered while digging through a BAPI’s ABAP code will not guaranty that. Direct access to standard tables via a SQL statement is even worse.
• What happens when SAP adds new functionality? If you followed the rules above, your application will still work, but you will need to add the new functionality (if your customers require it). Maybe you have a few months time before you add the new functionality to your application – you need to develop it, you have to test it and you have to ship it. But shipping it later should not that big of a problem – your customers did not have the functionality in the past, so they can live without it for another few months.
• But what when you have to deliver something on a fixed date, maybe at the same time that SAP is releasing it? I’m talking for example about legal changes in SAP Travel Management. If there is a new law and it is implemented the 1st January, your software must support it. And if SAP is releasing this functionality only in December, what will you do? If it is only customizing, that must be changed, your application can react on that, but what if the legal change requires a new data structure, new database tables to be available (like the change in Germany for the 90-day rule)?

This is the main challenge I see with SAP Travel Management. Most other processes are pretty static – Timesheet, CRM or field service are changing, but the pressure from customers is not that high. They have implemented something and if a new feature is added by SAP, they evaluate it. If it is worth for them to implement, they will do it. But if there is a legal change in the travel expenses area, they are forced to implement it asap.

Now I’m not only talking about mobile applications, but any type of third party solution that connects to travel management: Web UI’s, Rich Desktop Clients and even enhanced solutions of the standard ESS scenario.

I do not have a solution for this; I’m still searching ...