Bisame/database/migrations/2016_03_13_151917_create_annotation_table.php

<?php

use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateAnnotationTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('annotations', function (Blueprint $table) {
            $table->increments('id');
            $table->integer('confidence_score');
            $table->integer('user_id')->unsigned()->nullable();
            $table->integer('word_id')->unsigned()->nullable();
            $table->integer('postag_id')->unsigned()->nullable();
            $table->foreign('user_id')->references('id')->on('users');
            $table->foreign('word_id')->references('id')->on('words');
            $table->foreign('postag_id')->references('id')->on('postags');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::drop('annotations');
    }
}