Hi Shibin
1. The selection type can influence the price, one can imagine that a manually-specified logical resource might cost more than an automatic resource. For this reason it can make sense to retain as a product characteristic. However I would agree with you that there is a case for allowing characteristics at Order level that don't need to be persisted in the inventory. This would require enhancements in the Open API model and also in the underlying SID information framework.
2. If you indeed choose to model selection type as a Product characteristic, then the CRM system will have the information in the catalog model, as a product spec characteristic. You would still need code in the CRM system to understand the semantic meaning of these valid values (auto, manual, token).
3. I am not sure that we have a good solution in the API model for characteristic mapping - we have the mapping at the level of specification (product spec is implemented by service specs and resource specs) but not for characteristics. The SID has explicit mapping between product characteristics and service (or resource) characteristics, and even between values. Probably this needs to be enhanced into the Open API model, and I have opened a JIRA issue to document this.
Hope it helps
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Jonathan Goldberg
Amdocs Management Limited
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