NW GW with "dynamic" service

Question

Hi,
we are planning a project with NW GW and UI5. This solution should be deployed in 23 countries. The onliest pitfall we see so far is the fact that the interfaces for two services are not 100% fixed but for 80-90%. They differ in some fields. To do things worse we are currently working on the first 4 countries and don't know which fields will be the 10-20% variable fields.
Currently we think about two solutions:
- Add some dummy fields (for different data types).
- We use for the fixed 80% the known data types and for the variable part we take some dummy-fields as string and interpret them in the NW GW service. 
How would you solve the issue? What do you think is the smartest solution for this purpose? What should I consider in this solution?
Greetings, Vanessa

Answer 1

Creating a purely Dynamic metadata would  not be possible. Since OData approach is like a "declarative meta model" - where you need to define before hand how the metadata would be.
Metadata related operations are always expensive, so Gateway caches the metadata for faster operations. A dynamic metadata [even if you manage some how !] would make things very slow, as every time the framework deals with a new metadata for the same service. You code will also become very dynamic / conditional and complex. So may be you can rethink on your approach.
I have never done it, for a try you may,
1.     Disable the cache in the Gateway level (from SPRO setting) [ this will impact all other services as well, I believe ] -- things are expected to become slow !!!!
2.     You can follow a code based approach , with conditions to render dynamic metadata every time it is called
3.      Dynamic handling in the Data provider class
4.      Dynamic UI to understand this Model
This would make things slow and complex.. but hopefully you would achieve something you want at a high cost.
Better approach would be To develop service with known fields and enhancing it when more fields are know. May be you can pass some information using the HTTP headers if needed.
Atanu