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I am new with Fiware technologies and I have read many documents regarding Orion Context Broker but is not clear for me if a context consumer can request from Orion Context Broker history values about an entity.

I mean that if the context consumer need the measurements from day 1 to day 10 from a single temperature sensor to make an analysis, can it request those values from Orion or the context consumer can only retrieved those values from the database that are stored?

Example image

Does Orion has this capability?

Maria
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The context base managed by Orion Context Broker corresponds to the current status of the system. In other words, if a given attribute of a given entity has a value and a new update changes that value, then the old one is overriden.

This is not a limitation of Orion, but a design principle, due to the responsability of storing historical context is on charge of other FIWARE components. In particular, Cygnus is used to persist such historical information. It plays the role of a context consumer, subscribing to Orion and storing data in several persistence backends (HDFS, CKAN, MySQL, MongoDB, etc.). It can be used in combination with Short Term Historic, that provides a REST API similar to Orion NGSIv1 API in order to get raw historical data and some basic aggregations (sum, average, etc.).

fgalan
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  • Thank you for your response! I understand that at any given time Orion keeps the most updated value of an entity, my question is if a context consumer can request through Orion history values for that entity instead of communicate directly with the database that those values are stored. I will include an image with an example of what I mean for better understanding. – Maria Jun 27 '18 at 13:07
  • No, is not working that way. You application would need to access the persistance backend (MySQL in the case of your picture) in order to get the history values. – fgalan Jun 27 '18 at 16:03