Keith M.

I joined later, but I can try to find out for you

The query abilities in SQL are robust enough. A language design for RDBMS has been adapted to fit other DB types and datatypes, for blobs and clobs, XML and JSON, LPGs. But if we use an extension to DML we rely on other DDLs. Language enhancements must be added to query engines, and can't be written in SQL.

Q: Are declarative rules languages used for adaptive programming?

Lisp has no standard query language per se, yet it is often the choice for building query languages and applications that support user queries. The flexibility of the language itself allows to separate data model and logic just enough and no more. Lisp languages have always been attractive to developers who appreciate DSLs and other forms of extensibility in applications. Examples: Emacs, Lisp machines, expert system shells. I haven’t done adaptive programming, but my favorite languages support FP and excel in some of the capabilities you mention. Rather than RDF standards-based QL, I’ve used general purpose languages to build and/or query KGs: Scala, Clojure, Common Lisp, OPS5 variants, Prolog. Most of those languages have most but not all of (recursion, modularity, polymorphism). Scala and Common Lisp shine in those areas. (I’m told the JVM puts the kibosh on efficient recursion optimizations.)

Great article! You could extrapolate from your points to a general theory of languages and super/sub-structures with regard to evolution of AI and user needs. I don’t look to query languages for the kind of flexibility you mention. I think that’s not a goal for QL designers. Sad, but true. Query scripts are modular to en extreme; they are brittle and require constant maintenance because logical data models are separate from query abilities and physical data models. SQL is entirely schizoid (DML vs DDL).