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| # How do ordered_members and members behave and interact | |
| # Setup | |
| col1 = Hydra::Works::Collection.new(id: 'c1') | |
| wrk1 = Hydra::Works::Work.new(id: 'w1') | |
| wrk2 = Hydra::Works::Work.new(id: 'w2') | |
| wrk3 = Hydra::Works::Work.new(id: 'w3') | |
| wrk4 = Hydra::Works::Work.new(id: 'w4') | |
| # 1. adding to members does NOT add to ordered members | |
| col1.members << wrk1 | |
| col1.members.size # => 1 -- w1 | |
| Array(col1.ordered_members).size # => 0 | |
| # 2. adding to ordered_members does add to members | |
| col1.ordered_members << wrk4 | |
| col1.members.size # => 2 -- w1, w4 (order unimportant) | |
| Array(col1.ordered_members).size # => 1 -- w4 | |
| # 3. adding the same object again to ordered_members does NOT add to members | |
| col1.ordered_members << wrk4 | |
| col1.members.size # => 2 -- w1, w4 (order unimportant) | |
| Array(col1.ordered_members).size # => 2 -- w4, w4 (precise order) | |
| # add a few more to work with for deletes | |
| col1.ordered_members << wrk2 | |
| col1.ordered_members << wrk3 | |
| col1.members.size # => 4 -- w1, w2, w3, w4 (order unimportant) | |
| Array(col1.ordered_members).size # => 4 -- w4, w4, w2, w3 (precise order) | |
| # 3. deleting from members does NOT effect ordered_members | |
| col1.members.delete(wrk3) | |
| col1.members.size # => 3 -- w1, w2, w4 (order unimportant) | |
| Array(col1.ordered_members).size # => 4 -- w4, w4, w2, w3 (precise order) | |
| # 4. deleting from ordered_members does NOT effect members | |
| col1.ordered_members.delete_at(2) | |
| col1.members.size # => 3 -- w1, w2, w4 (order unimportant) | |
| Array(col1.ordered_members).size # => 2 -- w4, w4, w3 (precise order) | |
Quick question: if proxies for ordering allow for multiple different orderings of the same members, is that accommodated in the API?
@baxter-brad Multiple orderings in PCDM are handled via extra objects. There's one ordering per pcdm:object
Blend of Approach 2 and 3
Approach 2 could become more intuitive with some adjustments to the API. Currently, it seems like there are two lists (members and ordered_members) being kept for one aggregation. They seem to effect each other in a non-intuitive way. There aren’t actually two lists, but the API treats them in a way that implies they are separate. Trey pointed out in another email that "#ordered_members is a convenience method for returning the proxyFor objects, in order, pointed at from the ordered list.”
A potential change to the API could strengthen the concept that members is a single aggregation. Method changes to support this could be a blend of Approach 2 and 3. Keep the infrastructure currently in place with Approach 2. Change the public methods to be those of Approach 3 where all changes are made to members to effect set operations and ordered list operations. col1.ordered_members would not be a valid call anymore. Instead views into the aggregation as a set or list would be handled by the following methods. NOTE: col1 is an example PCDM:Collection that has aggregation members.
- col1.members.set - returns each unique member which represents the set
- col1.members.ordered - returns only members that have proxies which implies ordering (under the covers, this can still be the code run in the current convenience method ordered_members for returning the proxyFor objects)
- col1.members - by itself returns all members whether they have a proxy or not. This will be a set if no ordering was ever added, a fully ordered list if ordering was always added, or a partially ordered list if some members were added with and some without ordering.
@tpendragon is that actually specified in PCDM?
Actual triples created in Fedora
NOTE: These examples only include triples related to PCDM, ORE, and LDP. Fedora keeps additional triples and each object has additional rdf types that aren't shown here.
Set: Add one work to a collection without order
Code to create set:
col1.members << work1
col1.members << work2
col1.members << work3
Triples in Fedora necessary to represent a set using ORE:
@prefix pcdm: <http://pcdm.org/models#> .
@prefix ore: <http://www.openarchives.org/ore/terms/> .
<http://localhost:8983/fedora/rest/dev/col-1> a pcdm:Collection ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-1> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-2> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-3> .
Triples in Fedora for LDP and ORE: (includes the ORE triples from above)
@prefix ldp: <http://www.w3.org/ns/ldp#> .
@prefix pcdm: <http://pcdm.org/models#> .
@prefix ore: <http://www.openarchives.org/ore/terms/> .
<http://localhost:8983/fedora/rest/dev/col-1> a pcdm:Collection, ldp:Container, ldp:RDFSource ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-1/members> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-1> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-2> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-3> .
<http://localhost:8983/fedora/rest/dev/col-1/members> a ldp:Container, ldp:IndirectContainer, ldp:RDFSource ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-1/members/2aa40a84-8011-4bcd-8167-15f115b55d06> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-1/members/62fc559f-641a-43dc-9951-8425ed690037> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-1/members/9cfcdcdd-ab10-4822-9293-c4e100fc96e8> ;
ldp:hasMemberRelation pcdm:hasMember ;
ldp:insertedContentRelation ore:proxyFor ;
ldp:membershipResource <http://localhost:8983/fedora/rest/dev/col-1> .
<http://localhost:8983/fedora/rest/dev/col-1/members/2aa40a84-8011-4bcd-8167-15f115b55d06> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-2> .
<http://localhost:8983/fedora/rest/dev/col-1/members/62fc559f-641a-43dc-9951-8425ed690037> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-3> .
<http://localhost:8983/fedora/rest/dev/col-1/members/9cfcdcdd-ab10-4822-9293-c4e100fc96e8> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-1> .
Fully Ordered List: Add three works to a collection with order
Code to create fully ordered list:
col2.ordered_members << work1
col2.ordered_members << work2
col2.ordered_members << work3
Triples in Fedora necessary to represent a fully ordered list using ORE:
@prefix pcdm: <http://pcdm.org/models#> .
@prefix ore: <http://www.openarchives.org/ore/terms/> .
@prefix iana: <http://www.iana.org/assignments/relation/> .
<http://localhost:8983/fedora/rest/dev/col-2> a pcdm:Collection ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-1> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-2> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-3> ;
iana:first <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099634570060> ;
iana:last <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638308040> .
<http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099634570060> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-1> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-2> ;
iana:next <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638588660> .
<http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638588660> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-1> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-2> ;
iana:prev <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099634570060> ;
iana:next <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638308040> .
<http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638308040> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-1> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-2> ;
iana:prev <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638588660> .
NOTE: Each of the list_source proxies should have an rdf type of ore:proxy. Not sure why they don't.
Triples in Fedora for LDP and ORE: (includes the ORE triples from above)
@prefix ldp: <http://www.w3.org/ns/ldp#> .
@prefix pcdm: <http://pcdm.org/models#> .
@prefix ore: <http://www.openarchives.org/ore/terms/> .
@prefix iana: <http://www.iana.org/assignments/relation/> .
@prefix dct: <http://purl.org/dc/terms/> .
<http://localhost:8983/fedora/rest/dev/col-2> a pcdm:Collection, ldp:Container, ldp:RDFSource ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-2/list_source> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-2/members> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-1> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-2> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-3> ;
iana:first <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099634570060> ;
iana:last <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638308040> .
<http://localhost:8983/fedora/rest/dev/col-2/members> a ldp:Container, ldp:IndirectContainer, ldp:RDFSource ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-2/members/bac2feff-8010-4011-9192-de0a79dd13f7> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-2/members/e148c0f5-3038-4311-b39f-0dc4eb7d783a> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-2/members/fd47fa85-08b4-4b27-86d0-329d7d8bc371> ;
ldp:hasMemberRelation pcdm:hasMember ;
ldp:insertedContentRelation ore:proxyFor ;
ldp:membershipResource <http://localhost:8983/fedora/rest/dev/col-2> .
<http://localhost:8983/fedora/rest/dev/col-2/members/bac2feff-8010-4011-9192-de0a79dd13f7> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-1> .
<http://localhost:8983/fedora/rest/dev/col-2/members/e148c0f5-3038-4311-b39f-0dc4eb7d783a> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-3> .
<http://localhost:8983/fedora/rest/dev/col-2/members/fd47fa85-08b4-4b27-86d0-329d7d8bc371> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-2> .
<http://localhost:8983/fedora/rest/dev/col-2/list_source> a ldp:Container, ldp:RDFSource ;
dct:hasPart <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099634570060> ;
dct:hasPart <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638308040> ;
dct:hasPart <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638588660> ;
iana:first <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099634570060> ;
iana:last <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638308040> .
<http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099634570060> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-1> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-2> ;
iana:next <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638588660> .
<http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638588660> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-1> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-2> ;
iana:prev <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099634570060> ;
iana:next <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638308040> .
<http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638308040> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-1> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-2> ;
iana:prev <http://localhost:8983/fedora/rest/dev/col-2/list_source#g70099638588660> .
Partially Ordered List: Add three works to a collection with order and 3 without order
Code to create partially ordered list:
col3.members << work1
col3.ordered_members << work2
col3.ordered_members << work3
col3.members << work4
col3.ordered_members << work5
col3.members << work6
Triples in Fedora necessary to represent a partially ordered list using ORE:
@prefix pcdm: <http://pcdm.org/models#> .
@prefix ore: <http://www.openarchives.org/ore/terms/> .
@prefix iana: <http://www.iana.org/assignments/relation/> .
<http://localhost:8983/fedora/rest/dev/col-3> a pcdm:Collection ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-1> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-2> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-3> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-4> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-5> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-6> ;
iana:first <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159014522900> ;
iana:last <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70158983424840> .
<http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159014522900> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-2> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-3> ;
iana:next <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159013851360> .
<http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159013851360> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-3> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-3> ;
iana:prev <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159014522900> ;
iana:next <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70158983424840> .
<http://localhost:8983/fedora/rest/dev/col-3/list_source#g70158983424840> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-5> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-3> ;
iana:prev <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159013851360> .
NOTE: Each of the list_source proxies should have an rdf type of ore:proxy. Not sure why they don't.
Triples in Fedora for LDP and ORE: (includes the ORE triples from above)
@prefix ldp: <http://www.w3.org/ns/ldp#> .
@prefix pcdm: <http://pcdm.org/models#> .
@prefix ore: <http://www.openarchives.org/ore/terms/> .
@prefix iana: <http://www.iana.org/assignments/relation/> .
@prefix dct: <http://purl.org/dc/terms/> .
<http://localhost:8983/fedora/rest/dev/col-3> a pcdm:Collection, ldp:Container, ldp:RDFSource ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-3/list_source> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-3/members> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-1> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-2> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-3> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-4> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-5> ;
pcdm:hasMember <http://localhost:8983/fedora/rest/dev/work-6> ;
iana:first <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159014522900> ;
iana:last <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70158983424840> .
<http://localhost:8983/fedora/rest/dev/col-3/members> a ldp:Container, ldp:IndirectContainer, ldp:RDFSource ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-3/members/b362baa2-f803-4c6b-b8e8-44a25d64ea71> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-3/members/be70870b-54c1-4632-8347-d685ec756d44> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-3/members/c845ffbd-cdc3-42ca-8334-6f61cc20b9c3> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-3/members/d74e2ea1-dd0d-48b9-a5d7-942d732fc06b> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-3/members/e0ffc9a7-8934-4ce0-995f-a9ac8d93f554> ;
ldp:contains <http://localhost:8983/fedora/rest/dev/col-3/members/e1bf5600-860d-47cb-bad4-0326a9376c0a> ;
ldp:hasMemberRelation pcdm:hasMember ;
ldp:insertedContentRelation ore:proxyFor ;
ldp:membershipResource <http://localhost:8983/fedora/rest/dev/col-3> .
<http://localhost:8983/fedora/rest/dev/col-3/members/b362baa2-f803-4c6b-b8e8-44a25d64ea71> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-1> .
<http://localhost:8983/fedora/rest/dev/col-3/members/be70870b-54c1-4632-8347-d685ec756d44> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-3> .
<http://localhost:8983/fedora/rest/dev/col-3/members/c845ffbd-cdc3-42ca-8334-6f61cc20b9c3> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-2> .
<http://localhost:8983/fedora/rest/dev/col-3/members/d74e2ea1-dd0d-48b9-a5d7-942d732fc06b> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-4> .
<http://localhost:8983/fedora/rest/dev/col-3/members/e0ffc9a7-8934-4ce0-995f-a9ac8d93f554> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-6> .
<http://localhost:8983/fedora/rest/dev/col-3/members/e1bf5600-860d-47cb-bad4-0326a9376c0a> a ore:Proxy, ldp:Container, ldp:RDFSource ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-5> .
<http://localhost:8983/fedora/rest/dev/col-3/list_source> a ldp:Container, ldp:RDFSource ;
dct:hasPart <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70158983424840> ;
dct:hasPart <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159013851360> ;
dct:hasPart <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159014522900> ;
iana:first <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159014522900> ;
iana:last <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70158983424840> .
<http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159014522900> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-2> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-3> ;
iana:next <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159013851360> .
<http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159013851360> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-3> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-3> ;
iana:prev <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159014522900> ;
iana:next <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70158983424840> .
<http://localhost:8983/fedora/rest/dev/col-3/list_source#g70158983424840> a ;
ore:proxyFor <http://localhost:8983/fedora/rest/dev/work-5> ;
ore:proxyIn <http://localhost:8983/fedora/rest/dev/col-3> ;
iana:prev <http://localhost:8983/fedora/rest/dev/col-3/list_source#g70159013851360> .
The set of triples that are being generated in Fedora do not appear to match the concept of Resource Map described in the ORE spec. If you see this differently, can you explain how you understand this implementation to match ORE Resource Maps?
What is a use case for a partial_ordered list?
Approach 3: members
members
Terminology
members can be...
General expectation...
There is only one data structure and nothing to keep in sync.
The aggregation type is not codified by a triple value, but is a characteristic assessed by the triples that are used for members. An aggregation can change from a set to a partially ordered list by adding member(s) with order. A fully ordered list can be come a partially ordered list by adding member(s) without order.
Specific behaviors for add and delete...
Adding without order:
Adding with order:
NOTE: idx can be negative to be relative to the end of the list
Delete:
NOTE: nth can be negative to be relative to the end of the list