updated readme

Author: yorek

README.md

@@ -73,6 +73,11 @@ Once the application is running, you'll be able to ask question about your data
 Is there any session on Retrieval Augmented Generation?
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+You'll see that Langchain will call the function `get_similar_sessions` that behind the scenes connects to the database and excute the stored procedure `web.find_sessions` which perform vector search on database data.
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+The RAG process is defined using Langchain's LCEL (Langchain Expression Language)[https://python.langchain.com/v0.1/docs/expression_language/] that can be easily extended to include more complex logic, even including complex agent actions with the aid of [LangGraph](https://langchain-ai.github.io/langgraph/), where the function calling the stored procedure will be a [tool](https://langchain-ai.github.io/langgraph/how-tos/tool-calling/?h=tool) available to the agent.
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 ### Azure Functions (optional)
 
 TDB