Five ways to extend edX

Originally written by Sef ([email protected]), transcribed by Ned

Five Ways to Extend edX

I can think of five ways that someone could extend edX. Here they are in order of difficulty:

1. jsinput -- Create a "Custom JavaScript Grade and Display" component, and then provide JS with getState(), setState(), and getGrade() methods.
2. LTI -- edX supports LTI 1.1 now, LTI 2.0 in development
3. custom grader -- Code can be run on an external server to do arbitrary work to grade problems. With our Database Class we've had some success returning not just grades, but also an HTML block to be rendered with an answer. We return the query result, complete with HTML table formatting tags. See this screenshot as an example: the contents of the blue box is what was returned by the grader.
4. XBlock
5. hack on core code

Here’s my initial attempt at a grid to summarize , but I’m sure there are more rows that we’d want to consider:

	JSinput	LTI	External Grader	XBlock	Hack The Core!
Development Cost	Low	Low	Med	Med	High
Language	JS	any	any	Python	Python
Need dev environment	no	no	yes	yes	yes
Self-host component	no	yes	yes	no	no
Need edX involvement	no	no	yes	yes	yes
Clean UI Integration -- LTI components are basically iFramed in with their own UI, so their styling will probably not look right.	yes	no [1]	yes	yes	yes
Mobile friendly	maybe	maybe	yes	yes	yes
Server Side Grading	no [2]	yes	yes	yes	yes
Usage Data -- some basic logging exists for everything, this is for more detailed logs	no [3]	no	limited	yes (?)	yes
Provision in Studio -- the containers for all these kinds can be created from Studio, but only XBlocks re cleanly listed and configurable in Studio	no	no	no	yes	no
Privacy loss compared to the hosting of OpenEdX [4]	no	possibly [4]	possibly [4]	no	no

Notes:

• [1] Only LTI components delivered via https can be iframed in Many are served over http only. And even then they usually have their own look and feel. For example, Piazza can be iFramed in, but has its own navigation elements and their color scheme (see http://networking.class.stanford.edu/ for an example).
• [2] JSInput does have a small place where python could do server side grading, but doing it there would be pretty hacky and difficult to maintain.
• [3] JSInput really only exposes the getState, putState, getGrade methods. But is there any reason why we can’t also document / publish the tracking endpoint (/events/user_track I believe)
• [4] Privacy and secrecy issues are important in some areas of the world, and only becoming more important because of the news. If you have to self host OpenEdx because of that, this row indicates the guarantees that you can offer your students in that area. "Possibly" indicates that the guarantees will have to depend on the solution chosen for that particular use case. Note that both LTI and external graders allow for anonymization, but this might not be enough to allow for the use of some external tools within the constraints.