datalog: rose-ash demo programs (Phase 10 syntactic, 153/153)

New lib/datalog/demo.sx with three Datalog-as-query-language demos
over synthetic rose-ash data:

  Federation: (mutual A B), (reachable A B), (foaf A C) over a
              follows graph.
  Content:    (post-likes P N) via count aggregation, (popular P)
              for likes >= 3, (interesting Me P) joining follows
              + authored + popular.
  Permissions: (in-group A G) over transitive subgroup chains,
              (can-access A R).

10 tests run each program against in-memory EDB tuples loaded via
dl-program-data.

Wiring to PostgreSQL and exposing as a service endpoint (/internal
/datalog) is out of scope for this loop — both would require
edits outside lib/datalog/. Programs above document the EDB shape
a real loader would populate.

lib/datalog/conformance.conf

@@ -13,6 +13,7 @@ PRELOADS=(
   lib/datalog/strata.sx
   lib/datalog/eval.sx
   lib/datalog/api.sx
+  lib/datalog/demo.sx
 )
 
 SUITES=(
@@ -25,4 +26,5 @@ SUITES=(
   "negation:lib/datalog/tests/negation.sx:(dl-negation-tests-run!)"
   "aggregates:lib/datalog/tests/aggregates.sx:(dl-aggregates-tests-run!)"
   "api:lib/datalog/tests/api.sx:(dl-api-tests-run!)"
+  "demo:lib/datalog/tests/demo.sx:(dl-demo-tests-run!)"
 )

lib/datalog/demo.sx

@@ -0,0 +1,75 @@
+;; lib/datalog/demo.sx — example programs over rose-ash-shaped data.
+;;
+;; Phase 10 prototypes Datalog as a rose-ash query language. Wiring
+;; the EDB to actual PostgreSQL is out of scope for this loop (it
+;; would touch service code outside lib/datalog/), but the programs
+;; below show the shape of queries we want, and the test suite runs
+;; them against synthetic in-memory tuples loaded via dl-program-data.
+;;
+;; Three thematic demos:
+;;
+;;   1. Federation — follow graph, transitive reach, mutuals.
+;;   2. Content   — posts, tags, likes, popularity, "for you" feed.
+;;   3. Permissions — group membership and resource access.
+
+;; ── Demo 1: federation follow graph ─────────────────────────────
+;; EDB: (follows ACTOR-A ACTOR-B) — A follows B.
+;; IDB:
+;;   (mutual A B)            — A follows B and B follows A
+;;   (reachable A B)         — transitive follow closure
+;;   (foaf A C)              — friend of a friend (mutual filter)
+(define
+  dl-demo-federation-rules
+  (quote
+    ((mutual A B <- (follows A B) (follows B A))
+     (reachable A B <- (follows A B))
+     (reachable A C <- (follows A B) (reachable B C))
+     (foaf A C <- (follows A B) (follows B C) (!= A C)))))
+
+;; ── Demo 2: content recommendation ──────────────────────────────
+;; EDB:
+;;   (authored ACTOR POST)
+;;   (tagged POST TAG)
+;;   (liked ACTOR POST)
+;; IDB:
+;;   (post-likes POST N)            — count of likes per post
+;;   (popular POST)                 — posts with >= 3 likes
+;;   (tagged-by-mutual ACTOR POST)  — post tagged TOPIC by someone
+;;                                    A's mutuals follow.
+(define
+  dl-demo-content-rules
+  (quote
+    ((post-likes P N <- (authored Author P) (count N L (liked L P)))
+     (popular P <- (authored Author P) (post-likes P N) (>= N 3))
+     (interesting Me P
+       <-
+       (follows Me Buddy)
+       (authored Buddy P)
+       (popular P)))))
+
+;; ── Demo 3: role-based permissions ──────────────────────────────
+;; EDB:
+;;   (member ACTOR GROUP)
+;;   (subgroup CHILD PARENT)
+;;   (allowed GROUP RESOURCE)
+;; IDB:
+;;   (in-group ACTOR GROUP)         — direct or via subgroup chain
+;;   (can-access ACTOR RESOURCE)    — actor inherits group permission
+(define
+  dl-demo-perm-rules
+  (quote
+    ((in-group A G <- (member A G))
+     (in-group A G <- (member A H) (subgroup-trans H G))
+     (subgroup-trans X Y <- (subgroup X Y))
+     (subgroup-trans X Z <- (subgroup X Y) (subgroup-trans Y Z))
+     (can-access A R <- (in-group A G) (allowed G R)))))
+
+;; ── Loader stub ──────────────────────────────────────────────────
+;; Wiring to PostgreSQL would replace these helpers with calls into
+;; rose-ash's internal HTTP RPC (fetch_data → /internal/data/...).
+;; The shape returned by dl-load-from-edb! is the same in either case.
+(define
+  dl-demo-make
+  (fn
+    (facts rules)
+    (dl-program-data facts rules)))

lib/datalog/scoreboard.json

@@ -1,8 +1,8 @@
 {
   "lang": "datalog",
-  "total_passed": 143,
+  "total_passed": 153,
   "total_failed": 0,
-  "total": 143,
+  "total": 153,
   "suites": [
     {"name":"tokenize","passed":26,"failed":0,"total":26},
     {"name":"parse","passed":18,"failed":0,"total":18},
@@ -12,7 +12,8 @@
     {"name":"semi_naive","passed":8,"failed":0,"total":8},
     {"name":"negation","passed":10,"failed":0,"total":10},
     {"name":"aggregates","passed":10,"failed":0,"total":10},
-    {"name":"api","passed":9,"failed":0,"total":9}
+    {"name":"api","passed":9,"failed":0,"total":9},
+    {"name":"demo","passed":10,"failed":0,"total":10}
   ],
-  "generated": "2026-05-08T08:33:54+00:00"
+  "generated": "2026-05-08T08:45:37+00:00"
 }

lib/datalog/scoreboard.md

@@ -1,6 +1,6 @@
 # datalog scoreboard
 
-**143 / 143 passing** (0 failure(s)).
+**153 / 153 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
@@ -13,3 +13,4 @@
 | negation | 10 | 10 | ok |
 | aggregates | 10 | 10 | ok |
 | api | 9 | 9 | ok |
+| demo | 10 | 10 | ok |

lib/datalog/tests/demo.sx

@@ -0,0 +1,202 @@
+;; lib/datalog/tests/demo.sx — Phase 10 demo programs.
+
+(define dl-demo-pass 0)
+(define dl-demo-fail 0)
+(define dl-demo-failures (list))
+
+(define
+  dl-demo-deep=?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-demo-deq-l? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let ((ka (keys a)) (kb (keys b)))
+          (and (= (len ka) (len kb)) (dl-demo-deq-d? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-demo-deq-l?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-demo-deep=? (nth a i) (nth b i))) false)
+      (else (dl-demo-deq-l? a b (+ i 1))))))
+
+(define
+  dl-demo-deq-d?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i)))
+         (not (dl-demo-deep=? (get a k) (get b k))))
+        false)
+      (else (dl-demo-deq-d? a b ka (+ i 1))))))
+
+(define
+  dl-demo-set=?
+  (fn
+    (a b)
+    (and
+      (= (len a) (len b))
+      (dl-demo-subset? a b)
+      (dl-demo-subset? b a))))
+
+(define
+  dl-demo-subset?
+  (fn
+    (xs ys)
+    (cond
+      ((= (len xs) 0) true)
+      ((not (dl-demo-contains? ys (first xs))) false)
+      (else (dl-demo-subset? (rest xs) ys)))))
+
+(define
+  dl-demo-contains?
+  (fn
+    (xs target)
+    (cond
+      ((= (len xs) 0) false)
+      ((dl-demo-deep=? (first xs) target) true)
+      (else (dl-demo-contains? (rest xs) target)))))
+
+(define
+  dl-demo-test-set!
+  (fn
+    (name got expected)
+    (if
+      (dl-demo-set=? got expected)
+      (set! dl-demo-pass (+ dl-demo-pass 1))
+      (do
+        (set! dl-demo-fail (+ dl-demo-fail 1))
+        (append!
+          dl-demo-failures
+          (str
+            name
+            "\n    expected (set): " expected
+            "\n    got:            " got))))))
+
+(define
+  dl-demo-run-all!
+  (fn
+    ()
+    (do
+      ;; ── Federation ──────────────────────────────────────────
+      (dl-demo-test-set! "mutuals"
+        (dl-query
+          (dl-demo-make
+            (quote ((follows alice bob) (follows bob alice)
+                    (follows bob carol) (follows carol dave)))
+            dl-demo-federation-rules)
+          (quote (mutual alice X)))
+        (list {:X (quote bob)}))
+
+      (dl-demo-test-set! "reachable transitive"
+        (dl-query
+          (dl-demo-make
+            (quote ((follows alice bob) (follows bob carol) (follows carol dave)))
+            dl-demo-federation-rules)
+          (quote (reachable alice X)))
+        (list {:X (quote bob)} {:X (quote carol)} {:X (quote dave)}))
+
+      (dl-demo-test-set! "foaf"
+        (dl-query
+          (dl-demo-make
+            (quote ((follows alice bob) (follows bob carol) (follows alice dave)))
+            dl-demo-federation-rules)
+          (quote (foaf alice X)))
+        (list {:X (quote carol)}))
+
+      ;; ── Content ─────────────────────────────────────────────
+      (dl-demo-test-set! "popular posts"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((authored alice p1) (authored bob p2) (authored carol p3)
+               (liked u1 p1) (liked u2 p1) (liked u3 p1)
+               (liked u1 p2)))
+            dl-demo-content-rules)
+          (quote (popular P)))
+        (list {:P (quote p1)}))
+
+      (dl-demo-test-set! "interesting feed"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((follows me alice) (follows me bob)
+               (authored alice p1) (authored bob p2)
+               (liked u1 p1) (liked u2 p1) (liked u3 p1)
+               (liked u4 p2)))
+            dl-demo-content-rules)
+          (quote (interesting me P)))
+        (list {:P (quote p1)}))
+
+      (dl-demo-test-set! "post likes count"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((authored alice p1)
+               (liked u1 p1) (liked u2 p1) (liked u3 p1)))
+            dl-demo-content-rules)
+          (quote (post-likes p1 N)))
+        (list {:N 3}))
+
+      ;; ── Permissions ─────────────────────────────────────────
+      (dl-demo-test-set! "direct group access"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((member alice editors)
+               (allowed editors blog)))
+            dl-demo-perm-rules)
+          (quote (can-access X blog)))
+        (list {:X (quote alice)}))
+
+      (dl-demo-test-set! "subgroup access"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((member bob writers)
+               (subgroup writers editors)
+               (allowed editors blog)))
+            dl-demo-perm-rules)
+          (quote (can-access X blog)))
+        (list {:X (quote bob)}))
+
+      (dl-demo-test-set! "transitive subgroup"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((member carol drafters)
+               (subgroup drafters writers)
+               (subgroup writers editors)
+               (allowed editors blog)))
+            dl-demo-perm-rules)
+          (quote (can-access X blog)))
+        (list {:X (quote carol)}))
+
+      (dl-demo-test-set! "no access without grant"
+        (dl-query
+          (dl-demo-make
+            (quote ((member dave outsiders) (allowed editors blog)))
+            dl-demo-perm-rules)
+          (quote (can-access X blog)))
+        (list)))))
+
+(define
+  dl-demo-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-demo-pass 0)
+      (set! dl-demo-fail 0)
+      (set! dl-demo-failures (list))
+      (dl-demo-run-all!)
+      {:passed dl-demo-pass
+       :failed dl-demo-fail
+       :total (+ dl-demo-pass dl-demo-fail)
+       :failures dl-demo-failures})))