# 9.1. OLX Course Building Blocks¶

Before you begin using OLX (open learning XML) to set up a course, you should understand the building blocks of an edX course.

## 9.1.1. Courseware¶

Courseware is the main content of your course and consists mainly of lessons and assessments. The following list describes how courseware is organized in OLX.

• Course chapters are at the top level of your course and typically represent a time period. In Studio, chapters are called sections.
• A chapter contains one or more children which correspond to top-level pages in the course. In Studio, these are called ‘subsections’ and are currently restricted to sequential elements at this level. OLX supports any XBlock at this level.
• Courses are composed of structural elements, such as sequential and vertical, and leaf-nodes or content elements, such as html or problem. Studio has a fixed hierarchy where children of sequential elements are vertical elements (called units), and children of vertical elements are leaf elements (called modules).