Demonstration for how AffiliateWP registers a table to be compatible with the core metadata API.

class-affiliate-meta-db.php

<?php
/**
 * Core class used to implement affiliate meta.
 *
 * @since 1.6
 *
 * @see Affiliate_WP_DB
 */
class Affiliate_WP_Affiliate_Meta_DB extends Affiliate_WP_DB {

	/**
	 * Sets up the Affiliate Meta DB class.
	 *
	 * @access public
	 * @since  1.6
	*/
	public function __construct() {
		global $wpdb;

		$this->table_name  = $wpdb->prefix . 'affiliate_wp_affiliatemeta';

		add_action( 'plugins_loaded', array( $this, 'register_table' ), 11 );
	}

	// other code

	/**
	 * Registers the table with $wpdb so the metadata api can find it.
	 *
	 * @access public
	 * @since  1.6
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 */
	public function register_table() {
		global $wpdb;
		$wpdb->affiliatemeta = $this->table_name;
	}
}