English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Answering conjunctive queries (CQs) over $\mathcal{EL}$ knowledge bases (KBs)with complex role inclusions is PSPACE-hard and in PSPACE in certain cases;however, if complex role inclusions are restricted to role transitivity, thetight upper complexity bound has so far been unknown. Furthermore, the existingalgorithms cannot handle reflexive roles, and they are not practicable.Finally, the problem is tractable for acyclic CQs and $\mathcal{ELH}$, andNP-complete for unrestricted CQs and $\mathcal{ELHO}$ KBs. In this paper wecomplete the complexity landscape of CQ answering for several important cases.In particular, we present a practicable NP algorithm for answering CQs over$\mathcal{ELHO}^s$ KBs---a logic containing all of OWL 2 EL, but with complexrole inclusions restricted to role transitivity. Our preliminary evaluationsuggests that the algorithm can be suitable for practical use. Moreover, weshow that, even for a restricted class of so-called arborescent acyclicqueries, CQ answering over $\mathcal{EL}$ KBs becomes NP-hard in the presenceof either transitive or reflexive roles. Finally, we show that answeringarborescent CQs over $\mathcal{ELHO}$ KBs is tractable, whereas answeringacyclic CQs is NP-hard.

Answering Conjunctive Queries over $\mathcal{EL}$ Knowledge Bases with Transitive and Reflexive Roles