Any arbitrary string of Unicode characters would be a programming language given that above definition. Which makes of course no sense. A syntax without predef

Any arbitrary string of Unicode characters would be a programming language given that above definition. Which makes of course no sense. A syntax without predefined runtime semantics is not a programming language! Without the interpretation semantics no (or every, depending on standpoint) computation can be described by any syntax. The definition of runtime semantics for some syntax is what creates a programming language in the first place. Pure syntax OTOH can be given arbitrary interpretations. So it's therefore not a programming language on its own. The runtime semantic of some code is what allows us to write and execute programs. One can't write even the most trivial programs in JSON. No "Hello World" as JSON does not offer any I/O facility. No "fizzbuz" as there are no control structures or any loops in JSON. No "Fibonacci numbers" as there are no function abstractions in JSON… JSON is just not a programming language. (Still a valid candidate to include in computer language collection, of course, as JSON has its merits regardless the fact there is no canonical way do write in it anything that resembles computer programs).