--- a/light9/web/patch.test.ts	Mon May 29 11:44:22 2023 -0700
+++ b/light9/web/patch.test.ts	Mon May 29 11:44:54 2023 -0700
@@ -1,2 +1,45 @@
 import { assert, describe, expect, it } from "vitest";
 
+import { Quad, NamedNode } from "n3";
+import { Patch, QuadPattern } from "./patch";
+import * as N3 from "n3";
+
+const node1 = new NamedNode("http://example.com/node1");
+const node2 = new NamedNode("http://example.com/node2");
+const node3 = new NamedNode("http://example.com/node3");
+
+function QP(
+  subject: N3.Quad_Subject | null, //
+  predicate: N3.Quad_Predicate | null,
+  object: N3.Quad_Object | null,
+  graph: N3.Quad_Graph | null
+): QuadPattern {
+  return { subject, predicate, object, graph };
+}
+
+describe("Patch.matches", () => {
+  it("matches any quads against an open pattern", () => {
+    const quad1 = new Quad(node1, node2, node3);
+    const quad2 = new Quad(node1, node2, node3);
+    const quad3 = new Quad(node1, node2, node3);
+
+    const pattern = QP(null, null, null, null);
+
+    const p = new Patch([quad1, quad2], [quad3]);
+
+    assert.isTrue(p.matches(pattern));
+  });
+  it("doesn't match when the patch is empty", () => {
+    const p = new Patch([], []);
+    assert.isFalse(p.matches(QP(null, null, null, null)));
+  });
+  it("compares terms correctly", () => {
+    assert.isTrue(new Patch([new Quad(node1, node2, node3)], []).matches(QP(node1, null, null, null)));
+    assert.isFalse(new Patch([new Quad(node1, node2, node3)], []).matches(QP(node2, null, null, null)));
+  });
+  it("matches on just one set term", () => {
+    assert.isTrue(new Patch([new Quad(node1, node2, node3)], []).matches(QP(node1, null, null, null)));
+    assert.isTrue(new Patch([new Quad(node1, node2, node3)], []).matches(QP(null, node2, null, null)));
+    assert.isTrue(new Patch([new Quad(node1, node2, node3)], []).matches(QP(null, null, node3, null)));
+  });
+});

--- a/light9/web/patch.ts	Mon May 29 11:44:22 2023 -0700
+++ b/light9/web/patch.ts	Mon May 29 11:44:54 2023 -0700
@@ -2,6 +2,15 @@
 import debug from "debug";
 import * as N3 from "n3";
 import { NamedNode, Parser, Quad, Writer } from "n3";
+import { isEqualWith } from "lodash";
+
+export interface QuadPattern {
+  subject: N3.Quad_Subject | null;
+  predicate: N3.Quad_Predicate | null;
+  object: N3.Quad_Object | null; // literals allowed? needs review. probably 'yes'.
+  graph: N3.Quad_Graph | null;
+}
+
 const log = debug("patch");
 
 export class Patch {
@@ -31,6 +40,18 @@
     );
   }
 
+  matches(pat: QuadPattern): boolean {
+    const allQuads = this.dels.concat(this.adds);
+    return allQuads.some((quad) => {
+      return (
+        (pat.subject === null || pat.subject.equals(quad.subject)) && //
+        (pat.predicate === null || pat.predicate.equals(quad.predicate)) && //
+        (pat.object === null || pat.object.equals(quad.object)) && //
+        (pat.graph === null || pat.graph.equals(quad.graph))
+      );
+    });
+  }
+
   isEmpty() {
     return !this.dels.length && !this.adds.length;
   }