Re: definition of as:Collection and as:items very confused

items being marked as functional in the non - normative turtle is purely
accidental. Note that the normative text defined the actual definition. If
there are corrections you'd suggest to the turtle definition so that it is
a closer match to the text, PRs are helpful.
On Apr 24, 2015 1:28 AM, "henry.story@bblfish.net" <henry.story@bblfish.net>
wrote:

> as:Collection
> <http://www.w3.org/TR/activitystreams-vocabulary/#dfn-collection> contains
> one as:items <http://www.w3.org/TR/activitystreams-vocabulary/#dfn-items> which
> is defined as
>
> as:items a owl:ObjectProperty,
>            owl:FunctionalProperty ;
>   rdfs:label "items"@en ;
>   rdfs:domain as:Collection ;
>   rdfs:subPropertyOf prov:hadMember ;
>   rdfs:range [
>     a owl:Class ;
>     owl:unionOf (
>       [
>         a owl:Class ;
>         owl:unionOf ( as:Object as:LinkNotHandler )
>       ]
>       as:OrderedItems
>     )
>   ] .
>
> as:LinkNotHandler a owl:Class ;
>   rdfs:label "Links that are Not Handlers"@en ;
>   rdfs:subClassOf as:Link ,
>                   [ rdf:type owl:Class ;
>                     owl:complementOf as:ActivityHandler
>                   ] ;
>   rdfs:comment "Represents instances of as:Link that are not also as:ActivityHandler"@en .
>
> So some issues:
>
>    1. the domain of as:items is a as:Collection, which can only have one
>    element, namely the value of as:items . The spec says about as:items
>    <http://www.w3.org/TR/activitystreams-vocabulary/#dfn-items> that it "*Identifies
>    the items contained in a collection*" and "*The items might be ordered
>    or unordered*"
>    2. the range of as:items is the class which is the union of
>       - the class as:Object which is pretty much anything, since as:Object is
>       just defined as equivalent to prov:Entity which is defined as
>       <http://www.w3.org/ns/prov#Entity> "*a physical, digital,
>       conceptual, or other kind of thing with some fixed aspects; entities may be
>       real or imaginary*"
>       - the very specialised class of Links that are not activity
>       handlers
>       - ordered items
>
> This is very much the type of modelling error that someone who just got
> going in RDF but with a background in OO programming would make.
>
>    - Why bother creating an as:Collection which can contain only one
>    element, when RDF has a number of collections, and indeed when relations
>    themselves define collections: e.g. relations ( a.k.a predicates ) can be
>    one to one ( functional ) or one to many.
>    - why define a class that can contain pretty much anything and then on
>    top of that also some extremely particular things such as "Links that are
>    not activity handlers", and ordered collections. Are "Links that are not
>    activity handlers" something that has no fixed aspect? Are ordered items
>    things that have no fixed aspect?
>    - Why bother with ordered and unordered disctinction when RDF has the
>    tools to allow both, and JSON-LD was built to map those nicely to JSON?
>
> It looks to me like some simple attempt to go from modelling in OO
> programming to modelling in RDF, without taking into consideration the
> differences.
>
> as:items is an owl:FunctionalProperty and ends with  s which indicates
> that the authors were thinking in terms of object oriented programming
> fields. Fields can only have one value in OO. Collections are then modelled
> as objects containing an Array of objects that allow an index for each
> successive element, or recursively with Lists ( where each element can
> point to its successor ), or some combination of these ways of working.
>
> In RDF an object can have any number of relations of the same name: i.e. a
> relation can be one to many. One does not need to create a collection type
> with one attribute that can contain a collection. So for example the
> AtomOwl <http://bblfish.net/work/atom-owl/2006-06-06/AtomOwl.html> ontology
> allows the awol:entry relation to be one to many. Or in LDP an
> ldp:Collection can contain any number of ldp:contains elements that is
> one to many, i.e. one can write:
>
> <> a lpd:Collection;
>    ldp:contains <e1>, <e2>, <e3> .
>
> If one of these things contained something that was a List that could work
> too.
> So in short there is an abstraction here that is completely un-necessary,
> badly defined, and does not re-use any of the well known types developed in
> RDF to deal with these. It looks like the intention here is pretty much to
> provide what ldp:Containers do furthermore, so that one may not need to
> duplicate all this work.
>
> Social Web Architect
> http://bblfish.net/
>
>