Introduction

A history of messages is kept in the archive to allow for analysis of past events. Currently, the history is made available in NGSI-LD format. This allows for interoperability since this is linked data.

There are two ways to access the historical archive, with some different characteristics:

• Fast, but short term (approx. last 24 hours) Access via a NGSI-LD context broker with possibility to query the data and retrieve specific information. This is the fastest and most efficient way to retrieve the data.
• Slow, no query possible The historical data is stored in an Amazon S3 storage compatible location. The directory hierarchy is based on Date and type of message. Not for a specific use case

info

The storage in NGSI-LD format is due to be replaced by the more efficient Parquet format. This latter format allows a merely one to one translation of the original ASN.1 coded messages, but has the advantage that it is a wide accepted standard with libraries for the most common developer languages. Apart from development, it is compatible with data fromother mobility projects, like Smart City.

Access to the historical data is restricted. Even when there is no data involved what violates the privacy laws, this archive is not assumed to be open government data. Also caused by the fact that different suppliers are responsible for the data. In principle, the archive will be opened for research and gorvernment institutes. For access, please contact Mobilidata via the contact formular: Mobilidata

The extensive documentation is here

Data retention

There is a difference in retention times per message type and in the case of the context broker even the storage size behind it. The following tableprovides an overview. Changes are made without notification.

Location	Item	Retention period	Format
Context broker	MAPEM, DENM, IVIM	3 days up to 1 week	NGSI-LD
Historic data storage	MAPEM, DEM, IVIM	5 years	NGSI-LD
Side data storage	SPAT	3 months	JSON with base-64 body containing ASN.1 message