Constraint-based things to check out:<p>1. Sussman&#x27;s talk &quot;We Really Don&#x27;t Know How to Compute&quot; (<a href="http:&#x2F;&#x2F;www.infoq.com&#x2F;presentations&#x2F;We-Really-Dont-Know-How-To-Compute" rel="nofollow">http:&#x2F;&#x2F;www.infoq.com&#x2F;presentations&#x2F;We-Really-Dont-Know-How-T...</a>) and his work on the Propagator (<a href="https:&#x2F;&#x2F;github.com&#x2F;ProjectMAC&#x2F;propagators" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;ProjectMAC&#x2F;propagators</a>).<p>2. Gremlin Graph Traversal Machine (<a href="http:&#x2F;&#x2F;arxiv.org&#x2F;pdf&#x2F;1508.03843v1.pdf" rel="nofollow">http:&#x2F;&#x2F;arxiv.org&#x2F;pdf&#x2F;1508.03843v1.pdf</a>, <a href="http:&#x2F;&#x2F;www.datastax.com&#x2F;dev&#x2F;blog&#x2F;the-benefits-of-the-gremlin-graph-traversal-machine" rel="nofollow">http:&#x2F;&#x2F;www.datastax.com&#x2F;dev&#x2F;blog&#x2F;the-benefits-of-the-gremlin...</a>)<p>3. Clojure core.logic (<a href="https:&#x2F;&#x2F;github.com&#x2F;clojure&#x2F;core.logic" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;clojure&#x2F;core.logic</a>) and core.match (<a href="https:&#x2F;&#x2F;github.com&#x2F;clojure&#x2F;core.match" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;clojure&#x2F;core.match</a>)<p>4.  Yedalog: Exploring Knowledge at Scale (<a href="http:&#x2F;&#x2F;research.google.com&#x2F;pubs&#x2F;pub43462.html" rel="nofollow">http:&#x2F;&#x2F;research.google.com&#x2F;pubs&#x2F;pub43462.html</a>, <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=SP9zS43FRzQ" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=SP9zS43FRzQ</a>)<p>5. Datomic Datalog (<a href="http:&#x2F;&#x2F;docs.datomic.com&#x2F;query.html" rel="nofollow">http:&#x2F;&#x2F;docs.datomic.com&#x2F;query.html</a>)