UUID conventions

General

All records in Sahana Eden which shall be shared with other instances or applications must have a universally unique identifier (UUID).

In Sahana Eden, these record UUIDs must be ASCII strings.

Eden automatically generates a UUID for each record according to the specifications in RFC4122:

​http://www.faqs.org/rfcs/rfc4122.html

All record UUIDs generated by Sahana Eden are strings in URN notation:

urn:uuid:a46c1b3b-35c0-44c6-9142-bbe3a013039a

If a record is imported into Sahana Eden and it already has a UUID, then Eden will retain this UUID as-is (exception: local domain prefix, see below) - without any syntax validation. That means, no specific identifier schema is required. However: for consistency reasons, we recommend to use URNs even for other identifier schemas than UUID.

Domain Prefix

Some data formats (e.g. PFIF) may require a domain prefix for a UUID, followed by a slash:

sahanafoundation.org/urn:uuid:a46c1b3b-35c0-44c6-9142-bbe3a013039a

Where such a domain prefix is used and it matches the local domain of the importing Sahana instance, it will be removed during import.

In exports, the transformation stylesheets for formats which require a domain prefix will prepend the local domain to each un-prefixed UUID.

Mapping

We need an agreed set of UUIDs for GIS Data so that we can share data more easily across systems, such as the current Pakistan data

• OpenStreetMap IDs can change over time if records are deleted/recreated
  • They can ​hold additional uid/uuid fields though
• Geonames data isn't free enough for OSM: ​http://wiki.openstreetmap.org/wiki/Geonames
  • Geonet can be: ​http://wiki.openstreetmap.org/wiki/GEOnet_Names_Server
• Yahoo WoE data is in the public domain:
  • XML: ​http://code.flickr.com/blog/2009/05/21/flickr-shapefiles-public-dataset-10/
  • Tab: ​http://developer.yahoo.com/geo/geoplanet/data/
• Ushahidi doesn't have a common set of IDs across instances
  • No space for a UUID either?
• Longer-term we need a common central repository of UUIDs that is held for the common good.
  • Propose that Sahana start this off & then give up ownership/branding later:
  • Sahana can use UUIDs of format: ​http://geo.sahanafoundation.org/<ID>
  • These are associated with an OSM ID, Geonames ID & any Ushahidi instances for cross-correlation via the gis_location_tag table
  • The Source ID field shows the source, so that OSM export can filter out sources like Geonames

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