Taxonomies can be imported from external service providers
and locations.
A few samples are built-in, and more can be provided by
additional modules. Most supported services are direct URL
requests, usually with an identifier in the GET string
indicating the entry being requested. Others are simply URLs
(no ID argument needed) where a third-party document can be
downloaded from, provided as a convenience, or to avoid
licensing problems, and to ensure you are retrieving the
latest version.
Two forms of 'service' are currently supported - search and lookup. Both services are expected to return some form of unique identifer that can be used to locate further terms. A search result will return one or more ids that can be retrieved by lookup. A lookup may return a term definition that includes reference to its parent or child terms. These are usually looked up next.
Search is intended to take a text string and return a resource ID relevant to the service provider. Each service has its own form of local ID. It is the job of the service to identify the ID from the result and create an appropriate lookup request using that ID as a key.
Lookup is used when you have uniquely identified the resource entry to be retrieved, and returns a machine-readable dump of that data in one of the supported formats. Often that result will contain references to further resources that can be retrieved in turn.
The service definition array is undergoing development.