Linked Data on the Web Workshop, Lyon

(See the Workshop’s home page for details.)

The LDOW20** series have become more than workshops; they are really a small conferences. I did not count the number of participants (the meeting room had a fairly odd shape which made it a bit difficult) but I think it was largely over a hundred. Nice to see…

The usual caveat applies for my notes below: I am selective here with some papers which is no judgement on any other paper at the workshop. These are just some of my thoughts jotted down…

Giuseppe Rizzo made a presentation related to all the tools we know have to tag texts and thereby being able to use these resources in linked data (“NERD meets NIF: Lifting NLP Extraction Results to the Linked Data Cloud”), i.e., the Zemanta or Open Calais services of this World. As these services become more and more important, having a clear view of what they can do, how one can use them individually or together, etc., is essential. Their project, called NERD, will become an important source for this community, bookmark that page:-)

Jun Zhao made a presentation (“Towards Interoperable Provenance Publication on the Linked Data Web”) essentially on the work of the W3C Provenance Working Group. I was pleased to see and listen to this presentation: I believe the outcome of that group is very important for this community and, having played a role in the creation of that group, I am anxious to see it succeed. B.t.w., a new round of publication coming from that group should happen very soon, watch the news…

Another presentation, namely Arnaud Le Hors’ on “Using read/write Linked Data for Application Integration — Towards a Linked Data Basic Profile” was also closely related to W3C work. Arnaud and his colleagues (at IBM) came to this community after a long journey working on application integration; think, e.g., of systems managing software updates and error management. These systems are fundamentally data oriented and IBM has embarked into a Linked Data based approach (after having tried others). The particularity of this approach is to stay very “low” level, insofar as they use only basic HTTP protocol reading and writing RDF data. This approach seems to strike chord at a number of other companies (Elsevier, EMC, Oracle, Nokia) and their work form the basis of a new W3C Working Group that should be started this coming summer. This work may become a significant element of palette of technologies around Linked Data.

Luca Costabello talked about Access Control, Linked Data, and Mobile (“Linked Data Access Goes Mobile: Context-Aware Authorization for Graph Stores”). Although Luca emphasized that their solution is not a complete solution for Linked Data access control issues in general, it may become an important contribution in that area nevertheless. Their approach is to modify SPARQL queries “on-the-fly” by including access control clauses; for that purpose, an access control ontology (S4AC) has been developed and used. One issue is: how would that work with a purely HTTP level read/write Linked Data Web, like the one Arnaud is talking about? Answer: we do not know yet:-)

Igor Popov concentrated on user interface issues (“Interacting with the Web of Data through a Web of Inter-connected Lenses”): how to develop a framework whereby data-oriented applications can cooperate quickly, so that lambda users could explore data, switching easily to applications that are well adapted to a particular dataset, and without being forced to use complicated programming or use too “geeky” tools. This is still an alpha level work, but their site-in-development, called Mashpoint is a place to watch. There are (still) not enough work on user-facing data exploration tools, I was pleased to see this one…

What is the dynamics of Linked Data? How does it change? This is the question Tobias Käfer and his friends try to answer in future (“Towards a Dynamic Linked Data Observatory”). For that, data is necessary, and Tobias’ presentation was on how to determine what collection of resources to regularly watch and measure. The plan is to produce a snapshot of the data once a week for a year; the hope is that based on this collected data we will learn more about the overall evolution of linked data. I am really curious to see the results of that. One more reason to be at LDOW2013:-)

Tobias’ presentation has an important connection to the last presentation of the day, made by Axel Polleres (OWL: Yet to arrive on the Web of Data?) insofar as what he presented was based on the analysis of the Linked Data out there. The issue has been around, with lots of controversy, for a while: what level of OWL should/could be used for Linked Data? OWL 2 as a whole seems to be too complex for the amount of data we are talking about, both in terms of program efficiency and in terms of conceptually complexity for end users. OWL 2 has defined a much simpler profile, called OWL 2 RL, which does have some traction but may be still too complex, e.g., for implementations. Axel and his friends analyzed the usage of OWL statements out there, and also established some criteria on what type of rules should be used to make OWL processing really efficient; their result is another profile called OWL LD. It is largely a subset of OWL 2 RL, though it does adopt some datatypes that OWL 2 RL does not have.

There are some features that are left out of OWL 2 RL which I am not fully convinced of; after all their measurement was based on data in 2011, and it is difficult to say how much time it takes for new OWL 2 features to really catch up. I think that keys and property chains should/could be really useful on the Linked Data, and can be managed by rule engines, too. So the jury is still out on this, but it would be good to find a way to stabilize this at some point and see the LD crowd look at OWL (i.e., the subset of OWL) more positively. Of course, another approach would be to concentrate on an easy way to encode Rules into RDF which might make this discussion moot in a certain sense; one of the things we have not succeeded to do yet:-(

The day ended by a panel, on which I also participated; I would let others judge whether the panel was good or not. However, the panel was preceded by a presentation of Chris on the current deployment of RDFa and microdata which was really interesting. (His slides will be on the workshop’s page soon.) The deployment of RDFa, microdata, and microformats has become really strong now; structured data in HTML is a well established approach out there. RDFa and microdata covers now half of the cases, the other half being microformats, which seems to indicate a clear shift towards RDFa/microdata, ie, a more syntax oriented approach (with a clear mapping to RDF). Microdata is used almost exclusively with schema.org vocabularies (which is to be expected) whereas RDFa makes use of a larger palette of various other vocabularies. All these were to be expected, but it is nice to see being reflected in collected data.

It was a great event. Chris, Tim, and Tom: thanks!