update README.md

README.md

@@ -73,9 +73,10 @@ Extend Scryer Prolog to include the following, among other features:
   - [ ] Inlining all built-ins and system call instructions.
   - [x] Greatly reducing the number of instructions used to compile disjunctives.
   - [x] Storing short atoms to heap cells without writing them to the atom table.
+- [ ] Configurable JIT/on-demand indexing over all arguments
+      (documented in "[Demand-Driven Indexing of Prolog Clauses](https://user.it.uu.se/~kostis/Papers/iclp07.pdf)." (_in progress_)
 - [ ] A compacting garbage collector satisfying the five properties of
       "[Precise Garbage Collection in Prolog](https://www.complang.tuwien.ac.at/ulrich/papers/PDF/2008-ciclops.pdf)." (_in progress_)
-- [ ] Mode declarations.
 
 ## Phase 3
 
@@ -103,8 +104,6 @@ Gustafson's book "[The End of Error](http://www.johngustafson.net/unums.html)."
 3. Add concurrent tables to manage shared references to atoms and
 strings.
 
-4. Add some form of JIT predicate indexing.
-
 ## Installing Scryer Prolog
 
 ### Binaries