[esip-semantictech] Linked Data Notifications (LDN) and Software Implementations

[Mcgibbney, Lewis J (398M)]

Hi Tom,

CC esip-semanticweb@,
As we discussed yesterday after your presentation [0], there are lots of interesting use cases for a Linked Data Notifications (LDN) architecture across ESIP projects. I wanted to open this up to the community and have it on the mailing list so we can reference it moving forward.

What are Linked Data Notifications?
LDN [1] support sharing and reuse of notifications across applications, regardless of how they were generated. This allows for more modular systems, which decouple data storage from the applications which display or otherwise make use of the data. The protocol is intended to allow senders, receivers and consumers of notifications, which are independently implemented and run on different technology stacks, to seamlessly work together, contributing to decentralisation of our interactions on the Web.

Why would we care… provide a practical example of how we would use LDN?
Let’s take the COR for example… there are numerous areas where LDN could be utilized and helpful. Here are a few…

  1.  Say maintainers of the ENVO ontology are interested in changes to SWEET. Let’s also say they also have knowledge-based applications which utilize linked data to make decisions. This linked data relies upon accurate relationships between SWEET and ENVO. They want to be notified for any changes to SWEET such that their application behaves as expected. If a think LDN layer was layered over the COR then an incoming message regarding a change to SWEET would be persisted. The LDN service would then push a message to the ENVO client to notify of a change to SWEET and what that change was. The ENVO application could then react accordingly.
  2.  Say other data providers who are using COR are interested in being notified when any other new resource is stored within COR. Well, again, a LDN could be sent to any specific subscriber and they could act accordingly.
  3.  Say we run the AllegroGraph (the underlying RDF datastore powering COR) reasoning capability over data within COR and it results in linkages between resources. You would think the maintainers of the linked resources would want to know. Well with LDN, a push notification could be sent to those parties and action could be taken to address the data linkage.
  4.  … Tom you had a few more use cases which were related to provenance for connecting climate adaption decisions to data.

How does this fit in with COR?
Well for one, the above use cases justify that a notifications system would be useful. One of the underlying requirements of LDN is that all payloads MUST be encoded as JSON-LD, meaning that these message can be persisted within COR itself as amongst other things it is a native RDF store.

What software implementation could provide an LDN service?
As you would expect, the W3C editors draft [1] does not mention or endorse a specific software implementation. Loads of implementations do however exist at [3] meaning that a LDN service would probably not be difficult to establish as a thin layer over COR and hosted on in the same computing environment as COR.

How does this fit in with the Linked Data-as-a-Service initiative?
It actually harmonizes very nicely with the LDaaS initiative by offering a managed and hosted LDN service for data providers which compliments everything else we’ve described in the LDaaS effort thus far.

Tom, can you please chime in here and expand upon your use cases. It would be great to hear what your thoughts are.
Thank you, interesting presentation yesterday.
Lewis


[0] https://sched.co/JORx
[1] https://linkedresearch.org/ldn/
[2] https://allegrograph.com/products/allegrograph/
[3] https://github.com/search?q=linked+data+notifications



Dr. Lewis John McGibbney Ph.D., B.Sc.
Data Scientist II
Computer Science for Data Intensive Applications Group (398M)
Instrument Software and Science Data Systems Section (398)
Jet Propulsion Laboratory
California Institute of Technology
4800 Oak Grove Drive
Pasadena, California 91109-8099
Mail Stop : 158-256C
Tel:  (+1) (818)-393-7402
Cell: (+1) (626)-487-3476
Fax:  (+1) (818)-393-1190
Email: lewis.j.mcgibbney at jpl.nasa.gov<mailto:lewis.j.mcgibbney at jpl.nasa.gov>
ORCID: orcid.org/0000-0003-2185-928X

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