For a deeper look into our DataScope Select REST API, look into:
Overview | Quickstart | Documentation | Downloads | Tutorials
Attached is a working example that searches by CUSIP,and search by ISIN; modified from the DSS2SearchByRICClient example (part of the package, download link suggested by Rick).
These 2 samples were added to the Java code sample package today (available under the downloads tab). Note: they deliver multiple results (all possible RICs).
Have you reviewed the info at this link: https://developers.thomsonreuters.com/elektron-data-solutions/datascope-select-rest-api/downloads
Attached is a working example that converts 3 instrument codes (an Isin, a Sedol and a Cusip) to a RIC. For each input instrument it returns only 1 result, the primary RIC.
This sample was added to the Java code sample package today (available under the downloads tab).
An alternative paradigm is to use a TREP based symbology provider so that existing API users would simply call a new RIC for conversion. Additionally one could install ATS that could then provide transparent access to the Elektron content using the alternative symbology multiverse. Such a service would still need to be sourced from DataScope Select (DSS) or Tick History (TRTH) with an "Exchange By Day" (EBD) subscription.
Note in the not too distant future Elektron clients will be able to access such a featured service through the new REFERENCE domain.