# Learn 101

- 100: KEEPE IT SIMPLEME How works a hierarchical data lookup?

  - Query a key

  - Kheops is composed of 2 parts:

    - It will first look in different locations the key. It is usually files, but it can also be an url or anything.

  - Lookup data in a tree of files

    - Goes sequentially according the backends list

      - Backend/Engine list is modular

      - Engine Plugin: Jerakia/HIera/Ansible/Curl

      - Backend Plugin: loop/hier

    - All result are returned, and then the rules are applied

    - Rules match to a key and apply a strategy (essentially determine if and how the different value are merged or replaced). It can also apply filter to the result and modify its content (future).

      - This is modular

      - Strategy: last/schema

        - Last will always take the last found value, whatever what it previously found.

        - schema: It will take into account the strucutre of the data and try to merge them intelligentelly.

    - Then it returns the result