Writing Space is a learning application dedicated to the practice and assessment of writing, within the context of a course management system. At the heart of the tool is an online editor where papers are composed by students. The papers are submitted for assessment, either by other instructors, other integrated services, or by other students. One of the integrated services used to assess student papers is Turnitin (TII), a similarity checking service. Using TII's LTI launch, instructors opt-in to the service at an assignment level. Student submission content is then sent to TII, matched against a repository of student work and internet content, and optionally stored in TII's repository for future similarity checking. After assessing the submission content, TII returns a similarity score and report, which is accessible to the authoring student and instructor.