UUID conventions

General

UUIDs (Universal Unique IDentifiers) in Eden follow the Python uuid implementation, which is specified in RFC4122:

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

However, other systems do not necessarily follow this convention (especially data sets outside of IT systems), but we still must be able to identify such data resources.

Therefore, in every shared resource (XML+JSON), the UUID shall be prefixed by the domain name of the originating instance (authoritative domain) plus a slash ("/"), e.g.

    haiti.sahanafoundation.org/12345678-1234-5678-1234-567812345678

Generally, a "domain name" here can be any arbitraty XML name except it must not contain any slashes. However, the domain name must be unique, of course - and therefore it is recommended to use the internet domain name of the current instance. This in turn requires that all applications which share that domain name and take part in the data exchange adhere to the same UUID convention (UUID's have to be unique at least within the same domain).

This convention is adopted from the person_record_id convention of ​PFIF.

Implementation Guideline

At import, when the system receives a resource with a prefixed UUID and the prefix matches the domain of the current instance, then the prefix gets removed to identify the resource in the database. If the prefix differs from our domain, then the prefix is retained in the database record.

At export, all unprefixed UUIDs from the database get prefixed by the domain name of the current instance. In those UUIDs which already have a prefix (because they have been imported from another domain), the prefix is retained.

Mapping

We need an agreed set of UUIDs for GIS Data so that we can share data more easily across systems.

• 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 for cross-correlation
  • The Source ID field shows the source, so that OSM export can filter out sources like Geonames
  • IDs from Ushahidi instances can be appended to the comments field in Sahana

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DeveloperGuidelines