Hi Carl,
I am afraid the only real solutions here would be to either
1) Create a relationship class that bundles the object with an index, e.g.
:Article1 :maps_to :VideoItem1 .
:Article1 :maps_to :VideoItem2 .
:Article1 :maps_to :VideoItem3 .
:VideoItem1 a :VideoItem .
:VideoItem1 :video :Video1 .
:VideoItem1 sh:order 1 ;
:VideoItem2 a :VideoItem .
:VideoItem2 :video :Video2 .
:VideoItem2 sh:order 2 ;
:VideoItem3 a :VideoItem .
:VideoItem3 :video :Video3 .
:VideoItem3 sh:order 3 ;
2) Use rdf:Lists and add a widget that can handle them correctly. I
admit this is really a gap in the current UI support of EVN. We should
have better support for properties that have rdf:List as their value
type. It should arrange items in rows, but also have buttons to move
items up or down. I have recorded this as a requirement for a future
release. It's not a trivial amount of work but clearly needed if we want
to claim full RDF support.
Does this make sense?
FWIW if you want certain classes to appear in the Taxonomy editor, try
making them a subclass of skos:Concept (even if that's just a hack and a
temp triple).
Holger
On 26/05/2017 2:17, Carl Burnett wrote:
In certain situations, I would like our EVN users to be able to curate
ordered lists of concepts or other resources (most likely, content
assets). For example, a common scenario for us is to say that an
article maps to several videos, which ought to be presented (in some
downstream UI) in a fixed order. One way to do this would be to create
a resource representing the list of videos and then simply assign an
index to each video, like this:
:Article 1 :maps_to :VideoList .
:VideoList :contains :Video1, :Video2, :Video3 .
:Video1 :index 1 .
:Video2 :index 2 .
:Video3 :index 3 .
A problem with this approach is that we will want to create other
video lists in which the same videos appear in a different order.
When working in a SKOS vocabulary, Concept Collections
<https://www.w3.org/TR/skos-reference/#collections> would appear to be
a good solution to this problem. In TBC, it is no problem to model the
above scenario according to the SKOS standard:
:VideoList
rdf:type skos:OrderedCollection ;
skos:memberList (
:Video1
:Video2
:Video3
) .
Unfortunately, EVN Taxonomies seem to be unable to represent SKOS
collections at all; when I create one with this data, my resource
:VideoListis nowhere to be found – which makes sense, since EVN
Taxonomies display only Concepts and Concept Schemes, and
skos:Collections, by definition, are neither.
The situation is slightly better if I create the project as an EVN
Ontology: I can see that :VideoListis an instance of the class
skos:OrderedCollectionand that it has a member list. Unfortunately,
EVN does not seem to be able to represent the SKOS member list as
representing a set of known concept resources (screenshot
<http://imgur.com/O7E77Jm>), even though all of its members are
properly typed and labeled (screenshot <http://imgur.com/ALjDzUZ>).
I noticed that the domain of the property skos:memberList is declared
to be rdf:List, and it is true that the list I added in Composer is
not declared to be of that type. (Composer does not seem to mind
having an untyped list fill that slot.) So the next thing I tried was
to replace that list with a properly formatted rdf:List:
:VideoList
rdf:type skos:OrderedCollection ;
skos:memberList :AwesomeVideoList ;
rdfs:label “Video list” .
:AwesomeVideoList
rdf:type rdf:List ;
rdf:first :Video1 ;
rdf:rest [
rdf:first :Video2 ;
rdf:rest [
rdf:first :Video3 ;
] ;
] ;
rdfs:label "Awesome video list" .
Upon importing this data into an EVN project, I realized that I had
just pushed the problem down a level: my :VideoListordered collection
looks fine (screenshot <http://imgur.com/sxKje5Q>), but when I drill
into :AwesomeVideoList, it has again failed to resolve the Turtle list
syntax that describes the object of rdf:rest into an actual list of
typed and labeled resources (screenshot <http://imgur.com/CqBFn9e>).
It seems like the only way to get this work would be to create a
nested set of rdf:list resources, one for every item I want to include
in my list! (The last one would have no value for rdf:rest.)
Surely I’m not the first person to run across this problem. But EVN’s
docs say nothing at all about order. And searching the archives of
this discussion group, I only see questions about modeling order in
TBC (ex1
<https://groups.google.com/d/msg/topbraid-users/oGZNWKFrXmw/XHqXu2kSUIYJ>,
ex2
<https://groups.google.com/d/msg/topbraid-users/MRyr8wnrhSA/1XKvm7-W1poJ>),
not for EVN-managed data projects. Irene and Holger’s answers to ex2
are not exactly encouraging! (I think I am starting to understand Manu
Sporny’s disdain <http://manu.sporny.org/2014/json-ld-origins-2/> for
RDF’s treatment of lists.)
So. Does anyone have any suggestions for how I might model ordered
lists of resources in EVN? Simply replace the recursive “first/rest”
model that’s native to RDF with a more basic set of “previous/next”
properties? Or should I just resign myself to the caveman approach of
creating numbered sub-properties of the property whose values I want
to order (e.g., :contains_video_1, :contains_video_2, contains_video_3
… )?
___
*Carl Burnett***
Ontology Engineer | Healthwise
[email protected] <mailto:[email protected]> |
www.healthwise.org <http://www.healthwise.org/>
(208) 489-8485
*/Healthwise helps people make better health decisions/*/./
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