diff --git a/src/indicator.ts b/src/indicator.ts
new file mode 100644
index 0000000..a778121
--- /dev/null
+++ b/src/indicator.ts
@@ -0,0 +1,6 @@
+import { Alpaca } from "./alpaca";
+
+export interface Indicator<T> {
+    name: string;
+    evaluate(alpaca: Alpaca): Promise<T>;
+}
diff --git a/src/strategy.ts b/src/strategy.ts
new file mode 100644
index 0000000..c8ea4af
--- /dev/null
+++ b/src/strategy.ts
@@ -0,0 +1,15 @@
+import { Alpaca } from "./alpaca";
+
+export type SignalDirection = 'buy' | 'sell';
+
+export interface Signal {
+    symbol: string;
+    direction: SignalDirection;
+    allocation: number; // fraction of this strategy's capital to use (0-1)
+}
+
+export interface Strategy {
+    name: string;
+    capitalAllocation: number; // fraction of total account capital (0-1)
+    execute(alpaca: Alpaca): Promise<Signal[]>;
+}