First-order logic is necessary and sufficient to specify any and every program that runs on a digital computer.  But OWL 2 is limited, quirky, and far more difficult to learn and use that FOL.

Recommendation:  Design OWL 3 as exactly compatible with the OWL 2 hierarchy, but replace Turtle or other notations for the constraint language with an easy to read, write, and remember version of FOL.  For upward compatibility, keep all the OWL 2 features and syntax as an option which shall remain available in all future upgrades to OWL 3.

Syntax for the OWL 3 constraint language:   The reserved words and phrases that are used to represent constraints:  Some; Every; and; or; not; if... then,,,; only if; if and only if.

Every statement in the constraint language shall be a syntactically correct English sentence, which uses the reserved words above plus whatever words or symbols anybody chooses to represents entities in the subject domain.

Result:  Statements in the constraint language may be read without any training by anybody who can read English.  Learning to write the constraint language will require much less training than learning to write anything in OWL 2.

Observation:  The very intelligent logicians who designed OWL 1 and 2, made an incorrect assumption about issues of decidability.  

(1) undecidable statements are very complex, and nobody but a highly trained and knowledgeable logician would know how to write one,; 99.99% of software developers would not know how to read or write such a statement.  

(2) Undecidable statements only cause a problem for a theorem prover; they would NEVER cause any problem if and when they are used to state a constraint and use a constraint.

(3) But the syntactic constraints to prevent undecidable statements cause Turtle and other notations to become far more complex, unreadable, and unwritable than pure simple FOL expressed as English sentences, 

(4) For authors who do not read or write English, it's easy to specify exactly equivalent versions in every language spoken at the United Nations.  Every one of those versions would have a simple and efficient translation to the English version.

John