[Archivesspace_Users_Group] Retrieving tree info via API (what are "waypoints"?)

[Trevor Thornton]

Hi everybody-

I'm building a service using these API endpoints (or I think I am):
[:GET] /repositories/:repo_id/resources/:id/tree/root
<http://archivesspace.github.io/archivesspace/api/#fetch-tree-information-for-the-top-level-resource-record>
[:GET] /repositories/:repo_id/resources/:id/tree/node
<http://archivesspace.github.io/archivesspace/api/#fetch-tree-information-for-an-archival-object-record-within-a-tree>

These incorporate the concept of "waypoints", which I admit that I'm not
familiar with in this context, and it isn't explained very well in the
documentation. This is what I have to work with (these are elements
included in the API response):

   - child_count – the number of immediate children
   - waypoints – the number of “waypoints” those children are grouped into
   - waypoint_size – the number of children in each waypoint
   - precomputed_waypoints – a collection of arrays (keyed on child URI) in
   the same format as returned by the ’/waypoint’ endpoint. Since a fetch for
   a given node is almost always followed by a fetch of the first waypoint,
   using the information in this structure can save a backend call.

Can anyone explain what exactly waypoints are and how they are different
from children? In the examples I've seen, the "precomputed_waypoints"
element in the response looks like a convoluted way (an array value of the
lone element in an object, which is itself the value of the lone element in
another object) to provide the children nodes of the given node (or root).
What's the difference?

Thanks,
Trevor

-- 
Trevor Thornton
Applications Developer, Digital Library Initiatives
North Carolina State University Libraries
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