diff --git a/src/index.ts b/src/index.ts
index 87a110b..4a66d9b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,14 +1,23 @@
-import { createLogger, transports, format } from "winston";
+import { PortfolioProvider } from "./interface/portfolio";
+import { QuoteProvider } from "./interface/quote";
 
-const logger = createLogger({
-    transports: [new transports.Console()],
-    format: format.combine(
-      format.colorize(),
-      format.timestamp(),
-      format.printf(({ timestamp, level, message }) => {
-        return `[${timestamp}] ${level}: ${message}`;
-      })
-    ),
-  });
-  
-logger.info("Hello world!");
\ No newline at end of file
+/**
+ * Represents an exchange, which provides access to a portfolio provider and a quote provider.
+ */
+export interface Exchange {
+
+    /**
+     * The portfolio provider for the exchange.
+     */
+    readonly portfolioProvider: PortfolioProvider;
+
+    /**
+     * The quote provider for the exchange.
+     */
+    readonly quoteProvider: QuoteProvider;
+
+    /**
+     * The name of the exchange.
+     */
+    readonly name: string;
+}
diff --git a/src/interface/portfolio.ts b/src/interface/portfolio.ts
new file mode 100644
index 0000000..f65e153
--- /dev/null
+++ b/src/interface/portfolio.ts
@@ -0,0 +1,99 @@
+/**
+ * Represents a financial position in a portfolio.
+ */
+export class Position {
+    /**
+     * The price of the last trade made for this position.
+     */
+    readonly lastTrade: number;
+
+    /**
+     * The date and time of the last trade made for this position.
+     */
+    readonly lastTradeTime: Date;
+
+    /**
+     * The change in the position value.
+     */
+    readonly change: number;
+
+    /**
+     * The percentage change in the position value.
+     */
+    readonly changePercent: number;
+
+    /**
+     * The earnings per share of the position.
+     */
+    readonly earningsPerShare: number;
+
+    /**
+     * The market capitalization of the position.
+     */
+    readonly marketCap: number;
+
+    /**
+     * The symbol of the position.
+     */
+    readonly symbol: string;
+
+    /**
+     * Represents a position in a portfolio.
+     * @constructor
+     * @param {number} lastTrade - The price of the last trade made for this position.
+     * @param {Date} lastTradeTime - The date and time of the last trade made for this position.
+     * @param {number} change - The change in the position value.
+     * @param {number} changePercent - The percentage change in the position value.
+     * @param {number} earningsPerShare - The earnings per share of the position.
+     * @param {number} marketCap - The market capitalization of the position.
+     * @param {string} symbol - The symbol of the position.
+     */
+    constructor(
+        lastTrade: number,
+        lastTradeTime: Date,
+        change: number,
+        changePercent: number,
+        earningsPerShare: number,
+        marketCap: number,
+        symbol: string
+    ) {
+        this.lastTrade = lastTrade;
+        this.lastTradeTime = lastTradeTime;
+        this.change = change;
+        this.changePercent = changePercent;
+        this.earningsPerShare = earningsPerShare;
+        this.marketCap = marketCap;
+        this.symbol = symbol;
+    }
+}
+
+/**
+ * Represents a portfolio of financial positions.
+ */
+export class Portfolio {
+    /**
+     * An array of positions held in the portfolio.
+     */
+    readonly positions: Position[];
+
+    /**
+     * Creates a new Portfolio instance.
+     * @constructor
+     * @param {Position[]} positions - An array of Position objects representing the positions in the portfolio.
+     */
+    constructor(positions: Position[]) {
+        this.positions = positions;
+    }
+}
+
+/**
+ * A provider for fetching a portfolio.
+ */
+export interface PortfolioProvider {
+
+    /**
+     * Fetches the portfolio.
+     * @returns A promise that resolves with the fetched portfolio.
+     */
+    readonly fetchPortfolio: () => Promise<Portfolio>;
+}
diff --git a/src/interface/quote.ts b/src/interface/quote.ts
new file mode 100644
index 0000000..62b32e0
--- /dev/null
+++ b/src/interface/quote.ts
@@ -0,0 +1,65 @@
+/**
+ * Represents a stock quote.
+ */
+export class Quote {
+    /**
+     * The name of the company associated with this quote.
+     */
+    readonly companyName: string;
+
+    /**
+     * The earnings per share of a company.
+     */
+    readonly earningsPerShare: number;
+
+    /**
+     * The estimated earnings for a stock.
+     */
+    readonly estimatedEarnings: number;
+
+    /**
+     * The price of the last trade for the security.
+     */
+    readonly lastTrade: number;
+
+    /**
+     * The symbol of the financial instrument being quoted.
+     */
+    readonly symbol: string;
+
+    /**
+     * Represents a quote for a particular stock.
+     * @constructor
+     * @param {string} companyName - The name of the company associated with the stock.
+     * @param {number} earningsPerShare - The earnings per share for the stock.
+     * @param {number} estimatedEarnings - The estimated earnings for the stock.
+     * @param {number} lastTrade - The last trade price for the stock.
+     * @param {string} symbol - The symbol for the stock.
+     */
+    constructor(
+        companyName: string,
+        earningsPerShare: number,
+        estimatedEarnings: number,
+        lastTrade: number,
+        symbol: string
+    ) {
+        this.companyName = companyName;
+        this.earningsPerShare = earningsPerShare;
+        this.estimatedEarnings = estimatedEarnings;
+        this.lastTrade = lastTrade;
+        this.symbol = symbol;
+    }
+}
+
+/**
+ * A provider for fetching stock quotes.
+ */
+export interface QuoteProvider {
+
+    /**
+     * Fetches a quote for the given stock symbol.
+     * @param symbol The stock symbol to fetch the quote for.
+     * @returns A Promise that resolves to a Quote object.
+     */
+    readonly fetchQuote: (symbol: string) => Promise<Quote>;
+}