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Re: I really hate RDF Lists

From: Scott Bauer <Bauer.Scott@mayo.edu>
Date: Fri, 4 May 2012 08:35:29 -0500
Cc: RDF WG <public-rdf-wg@w3.org>
Message-Id: <91AB920A-9CAE-47C5-BA6B-265C4E94DC7D@mayo.edu>
To: Manu Sporny <msporny@digitalbazaar.com>
Mayo has similar problems integrating RDF List into the CTS2 implementation.  
+1 to some changes on this even though I know it's not on our list of things to get done.


On May 3, 2012, at 11:11 PM, Manu Sporny wrote:

> The subject of the e-mail is a bit tongue-in-cheek, but after being
> forced to work with RDF lists in the RDFa work and now again in the
> JSON-LD work - I really, truly hate the way RDF Lists are modeled.
> Just a few anecdotes to why:
> * The addition of RDF List processing is one of the most complex
>  features of RDFa 1.1 and the triples that are generated are nearly
>  useless in their raw form to developers. It took me a full 38 hours
>  to implement support for it in librdfa - which was the grand total
>  amount of time that it took me to implement the first cut of the
>  librdfa processor in C. Yes, this is partly due to the difficulty
>  of expressing a list in a hierarchical document expressing RDF,
>  but even the resulting triples just make no sense to someone that
>  isn't a programmer. You can't expect Web developers to know what
>  a linked list is.
> * The addition of RDF List processing in JSON-LD created many hours
>  of head-scratching and pain because of the awkwardness of the
>  RDF data model when it comes to lists. It also prevented us from
>  implementing lists of lists because the algorithm to do so became
>  fantastically complex - corner cases related to lists started
>  mounting fairly quickly and we had to fence the work to not fall
>  into the endless pit of RDF List related issues.
> * We went out of our way to not support RDF Lists in the PaySwarm
>  implementations we've been doing. It was only when we created JSON-LD
>  did we figure out a way to use them without having to give
>  everybody that didn't know anything about RDF, who wanted to
>  learn the PaySwarm API, a lesson in RDF Lists 101. The solution was
>  to hide RDF Lists from developers entirely.
> In summary - RDF Lists are difficult to implement, even for people that
> know quite a bit about RDF. They are fantastically difficult to grasp
> for Web developers. They are really hard to author in many of the RDF
> syntaxes.
> I'd like to propose something that the group should seriously consider:
> 1. Add lists as a first-class citizen for all RDF serializations -
> deprecate all serializations that don't support lists as first-class
> citizens.
> 2. Get rid of the the Seq, Bag and List classes - replace with two
> datatypes - rdf:ordered and rdf:unordered. All "lists" in RDF are
> ordered by default.
> So, N-Triples and N-Quads could look something like this:
> # ordered list
> <s> <p> ["O1", "O2"@ja, <http://example.org/>] .
> # unordered list
> <s> <p> ["01", "O2"@ja, <http://example.org/>]^^rdf:unordered .
> or even:
> # ordered list
> <s> <p> ["O1", "O2"@ja, <http://example.org/>] .
> # unordered list
> <s> <p> ("01", "O2"@ja, <http://example.org/>) .
> If we had started with this, it would mean that RDF Lists would have a
> direct mapping to JSON (which got lists right, IMHO). The beauty of JSON
> is that by default, the list has order... and if you don't care about
> order, you just process the list in any order. If you care about order,
> start from the beginning and go to the end. JSON got lists right because
> they make the default case ordered and the corner-case unordered. RDF
> did it backwards and got it wrong.
> While this idea isn't fully baked, I've been sitting on it for two years
> now and thought I should send it out while I was still agitated about
> having to foist RDF Lists onto Web developers. This is one of those bits
> of RDF that has been hurting the cause for over a decade. Surely, this
> has been discussed before? Anyone have a link?
> -- manu
> -- 
> Manu Sporny (skype: msporny, twitter: manusporny)
> President/CEO - Digital Bazaar, Inc.
> blog: PaySwarm Website for Developers Launched
> http://digitalbazaar.com/2012/02/22/new-payswarm-alpha/
Received on Friday, 4 May 2012 13:35:57 UTC

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