Immersion is a slippery term, but in the context of transmedia narratives it usually refers to spaces that allow audiences to enter the world of the story, whether that space be virtual or realized in a theme park environment .  Extractability refers to an audience member's ability to take a token or physical object from a story with them as a resource for their own expansion or play .  In some cases, these principles are deployed to work in tandem .

Henry Jenkins argues that simply replicating classroom environments in virtual spaces doesn't constitute an "immersive" experience for students .  Rather, an "immersive" approach to education might have students moving through virtual spaces, or building their own to theorize the importance of what these virtual spaces contain, and how we move through them.  Joel Levin, "The Minecraft Teacher," has effectively employed this principle in grade school classrooms, leading to the development of MinecraftEdu .  There are also enduring benefits of a tangible "show-and-tell" system in which extracted objects are contextualized and shared publicly.  For example, Melanie Kohnen, in her transmedia television course at Georgia Tech, encouraged her students to create extractable extensions of their final projects.

Extractability in this model might not involve physical objects, and instead be extrapolated to include digital resources and tools used to build transmedia scholarship.  We might consider ProfHacker as a model for this particular type of "show-and-tell" space.  Alternately, the recent push towards "making" in the Digital Humanities could help realize these "extractable" elements in a transmedia project.  Immersion in this context might require similar terminological flexibility, focused less on our movement through virtual or real spaces, and more on our movement through the transmedia project and building an immersive experience for readers.     

USC's Pervasive Game "Reality Ends Here"