AH! Thanks 
I hadn’t needed to drill down to deeper levels on what I was initially using 
this endpoint for, so I didn’t catch onto the use of /tree/node?node_uri= 
Sounds right! 

— Steve. 


> On Jul 23, 2019, at 2:22 PM, Trevor Thornton <[email protected]> wrote:
> 
> First of all, great documentation (in the code, API documentation less so but 
> we're working on that) 👍
> 
> To close the loop on this thread (for anyone still interested):
> For what I'm doing I need the container info, which is included in the 
> .../tree/... responses. Basically I'm re-creating a version of the AS 
> resource tree to provide a browsable view of a resource hierarchy in another 
> application. So the process will be something like this (for a resource with 
> URI  /repositories/1/resources/123):
> Call  /repositories/1/resources/123/tree/root to get the resource-level data 
> and its children (up to 200)
> If the value for "waypoints" in the response is greater than 1, call 
> /repositories/1/resources/123/tree/waypoints&offset=n for each additional 
> waypoint (n = 1 through # of waypoints - 1) to get the rest of the children
> Then for each child record with other children, I'll provide a link to see 
> the next level, which will call 
> /repositories/1/resources/123/tree/node&node_uri=[URI OF THE RECORD THAT WAS 
> CLICKED]
> (NOTE: node_uri is a required parameter for this endpoint but that's not 
> mentioned in API the documentation)
> This provides a response similar to the .../tree/root endpoint but with data 
> for the archival object record instead of the resource
> Repeat step 2 if there is more than one waypoint at this level, including the 
> current node URI as parent_id in the GET params
> Repeat steps 3 & 4 until you get to the end
> I *think* this is close to right.
> 
> Thanks again for your help!
> 
> On Tue, Jul 23, 2019 at 12:51 PM Majewski, Steven Dennis (sdm7g) 
> <[email protected] <mailto:[email protected]>> wrote:
> 
> I believe for the next level of archival_objects, you have to get 
> /repositories/$REPO/archival_objects/$ID/children , but check the API docs.
> 
> 
> Note that there is also a GET 
> /repositories/$REPO/resources/$ID/ordered_records method that gives you the 
> whole hierarchy, but minimal info about each resource:  { ref: 
> display_string:, depth:, level: } 
> 
> I don’t think I knew about that one the first time I was wrestling with this 
> sort of task. 
> If you’re doing backend API and not worried about real time display update, 
> it might make more sense to walk the output ordered_records 
> If you want more complete info on resource children. 
> 
> 
> — Steve. 
> 
> 
>> On Jul 23, 2019, at 12:11 PM, Trevor Thornton <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>> Just found that file in the repo before I saw your message and I think I 
>> understand now - thanks!
>> 
>> So, if you're looking at a node below the root (an ArchivalObject) that has 
>> >200 children, you would hit the ".../tree/waypoint" endpoint however many 
>> times and include "parent_node" in the GET params with the ArchivalObject 
>> URI, right?
>> 
>> On Tue, Jul 23, 2019 at 11:57 AM Majewski, Steven Dennis (sdm7g) 
>> <[email protected] <mailto:[email protected]>> wrote:
>> 
>>> So the next question is how do you make the subsequent calls to retrieve 
>>> the next 200, etc.?
>> 
>> 
>> 
>> You call  /repositories/$repo/resources/$id/tree/waypoint?offset=$N  23 
>> times. 
>> ( You already got the first batch in .precomputed_waypoints in the call to 
>> /ress/root  ) 
>> 
>> 
>> I found the documentation note in the source I was looking for: 
>> https://github.com/archivesspace/archivesspace/blob/master/backend/app/model/large_tree.rb
>>  
>> <https://github.com/archivesspace/archivesspace/blob/master/backend/app/model/large_tree.rb>
>> 
>> 
>> # What's the big idea?
>> #
>> # ArchivesSpace has some big trees in it, and sometimes they look a lot like 
>> big
>> # sticks.  Back in the dark ages, we used JSTree for our trees, which in 
>> general
>> # is perfectly cromulent.  We recognized the risk of having some very large
>> # collections, so dutifully configured JSTree to lazily load subtrees as the
>> # user expanded them (avoiding having to load the full tree into memory right
>> # away).
>> #
>> # However, time makes fools of us all.  The JSTree approach works fine if 
>> your
>> # tree is fairly well balanced, but that's not what things look like in the 
>> real
>> # world.  Some trees have a single root node and tens of thousands of records
>> # directly underneath it.  Lazy loading at the subtree level doesn't save you
>> # here: as soon as you expand that (single) node, you're toast.
>> #
>> # This "large tree" business is a way around all of this.  It's effectively a
>> # hybrid of trees and pagination, except we call the pages "waypoints" for
>> # reasons known only to me.  So here's the big idea:
>> #
>> #  * You want to show a tree.  You ask the API to give you the root node.
>> #
>> #  * The root node tells you whether or not it has children, how many 
>> children,
>> #    and how many waypoints that works out to.
>> #
>> #  * Each waypoint is a fixed-size page of nodes.  If the waypoint size is 
>> set
>> #    to 200, a node with 1,000 children would have 5 waypoints underneath it.
>> #
>> #  * So, to display the records underneath the root node, you fetch the root
>> #    node, then fetch the first waypoint to get the first N nodes.  If you 
>> need
>> #    to show more nodes (i.e. if the user has scrolled down), you fetch the
>> #    second waypoint, and so on.
>> #
>> #  * The records underneath the root might have their own children, and 
>> they'll
>> #    have their own waypoints that you can fetch in the same way.  It's 
>> nodes,
>> #    waypoints and turtles the whole way down.
>> #
>> # All of this interacts with the largetree.js code in the staff and public
>> # interfaces.  You open a resource record, and largetree.js fetches the root
>> # node and inserts placeholders for each waypoint underneath it.  As the user
>> # scrolls towards a placeholder, the code starts building tracks ahead of the
>> # train, fetching that waypoint and rendering the records it contains.  When 
>> a
>> # user expands a node to view its children, that process repeats again (the 
>> node
>> # is fetched, waypoint placeholders inserted, etc.).
>> #
>> # The public interface runs the same code as the staff interface, but with a
>> # small twist: it fetches its nodes and waypoints from Solr, rather than from
>> # the live API.  We hit the API endpoints at indexing time and store them as
>> # Solr documents, effectively precomputing all of the bits of data we need 
>> when
>> # displaying trees.
>> 
>> 
>> 
>> 
>> 
>>> On Jul 23, 2019, at 11:08 AM, Trevor Thornton <[email protected] 
>>> <mailto:[email protected]>> wrote:
>>> 
>>> Thanks, Steve. That makes sense, and I tested with a resource with >1000 
>>> top level children and I see that only 200 of them are included, which 
>>> corresponds to the value for "waypoint_size" in the response:
>>> 
>>> {  
>>>    "child_count":4780,
>>>    "waypoints":24,
>>>    "waypoint_size":200
>>> ...
>>> 
>>> So the next question is how do you make the subsequent calls to retrieve 
>>> the next 200, etc.?
>>> 
>>> On Tue, Jul 23, 2019 at 10:52 AM Majewski, Steven Dennis (sdm7g) 
>>> <[email protected] <mailto:[email protected]>> wrote:
>>> I believe the rationale of the waypoints was that initially, it was 
>>> expected that resource children/ archival objects would fall into a more 
>>> balanced tree structure, but it turned out that there were many flat 
>>> hierarchies with hundreds of top level children, and getting all of the 
>>> children at once was not working very efficiently. So with they waypoint 
>>> calls, you may only be getting some of the children, but the display can 
>>> start populating the tree display while making additional calls for the 
>>> rest. 
>>> 
>>> I may have some postman examples and internal notes around somewhere: I’ll 
>>> see what I can dig out. 
>>> 
>>> — Steve. 
>>> 
>>> 
>>>> On Jul 23, 2019, at 9:05 AM, Trevor Thornton <[email protected] 
>>>> <mailto:[email protected]>> wrote:
>>>> 
>>>> 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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>>>> [email protected] 
>>>> <mailto:[email protected]>
>>>> http://lyralists.lyrasis.org/mailman/listinfo/archivesspace_users_group 
>>>> <http://lyralists.lyrasis.org/mailman/listinfo/archivesspace_users_group>
>>> 
>>> _______________________________________________
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>>> 
>>> 
>>> -- 
>>> Trevor Thornton
>>> Applications Developer, Digital Library Initiatives
>>> North Carolina State University Libraries
>>> _______________________________________________
>>> Archivesspace_Users_Group mailing list
>>> [email protected] 
>>> <mailto:[email protected]>
>>> http://lyralists.lyrasis.org/mailman/listinfo/archivesspace_users_group 
>>> <http://lyralists.lyrasis.org/mailman/listinfo/archivesspace_users_group>
>> 
>> _______________________________________________
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>> 
>> 
>> -- 
>> Trevor Thornton
>> Applications Developer, Digital Library Initiatives
>> North Carolina State University Libraries
>> _______________________________________________
>> Archivesspace_Users_Group mailing list
>> [email protected] 
>> <mailto:[email protected]>
>> http://lyralists.lyrasis.org/mailman/listinfo/archivesspace_users_group 
>> <http://lyralists.lyrasis.org/mailman/listinfo/archivesspace_users_group>
> 
> _______________________________________________
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> 
> 
> -- 
> Trevor Thornton
> Applications Developer, Digital Library Initiatives
> North Carolina State University Libraries
> _______________________________________________
> Archivesspace_Users_Group mailing list
> [email protected]
> http://lyralists.lyrasis.org/mailman/listinfo/archivesspace_users_group

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