DeKaloG: Decentralized Knowledge Graphs

DeKaloG follows the vision of a global decentralized knowledge graph that can be leveraged to answer questions at the scale of the web. For example, “give me information about people who know Tim Berners-Lee” or “What is the number of famous scientists men and women per birth year ?”. To face the LOD issues, DeKaloG promotes ATF (Accessibility, Transparency, and Findability) principles and a sustainable approach for implementing them:
(A)ccessibility is the right to execute any query at any time on a KG and get complete answers. Currently, accessibility is challenged by critical availability and scalability problems [30]. To ensure availability and fair access to KG, existing KG providers restrict access by reducing the expressivity of queries or implement fair access policies thanks to time quotas. Consequently, many queries cannot produce complete answers. For instance, asking for all entities in Wikidata will return a partial set of entities only. DeKaloG aims to propose a model to provide fair access policies to KGs without quota while ensuring complete answers to any query. Such property is crucial for enabling web automation, i.e. to allow agents or bots to interact with KGs. Preliminary results on web preemption [1] open such perspective, but scalability issues remain.
(T)ransparency ensures the right to know who built the KG, how it was built, and from which sources. Transparency requires data provenance information and more generally contextual information that are not widely adopted in the LOD [33,30]. Transparency can be defined at many levels from the whole KG down to individual facts within a KG. The trade-off between transparency granularity and query performance is still an open issue. DeKaloG aims to propose models for capturing different levels of transparency, a method to query them efficiently, and especially, techniques to enable web automation of transparency.
(F)indability is the right to find efficiently pertinent KGs for a query, i.e. which KGs contain relevant facts for the query. DeKaloG aims to propose a sustainable index for achieving the findability principle. The index itself is envisioned as an accessible and transparent KG, indexing accessible and transparent KGs. For the KG index, accessibility means any query can be executed on the index and get complete results. Transparency means that a KG provider can know what the index knows about her KG, including ranking statistics and how they are computed and mostly the reproducibility of the index. The originality is to interact with the index as a KG and also to build and maintain the index just by querying KGs.
The main idea behind ATF principles is to consider KGs as a first-class citizen and build a sustainable eco-system of KGs. ATF principles target the automation of the web of Knowledge Graphs. As Wikipedia’s bots contribute to the quality of Wikipedia, the principles of DeKaloG allow to write KG bots to maintain and improve the web of KGs. Enabling an open and sustainable global knowledge graph is essential to ensure access to open knowledge for citizens, organizations, and companies.

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