ROSLisp/ROSProlog/Knowrob-- Need CRAM for OWL? JSON? [closed]

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should I install SBCL and SWI Prolog in advance before even installing ROS?

SBCL is a system dependency of ROS, so you get it when you install ROS. SWI Prolog is installed when you rosdep install KnowRob.

If I install Knowrob, will ROSLisp, ROSProlog and JSON_prolog be installed as dependencies anyway?

roslisp comes with ROS, rosprolog and rosprolog side of json_prolog come with KnowRob.

Will it install CRAM too?

No.

Do I need to install CRAM at all?

json_prolog provides a JSON interface for rosprolog that works over ROS services. Once you roslaunch your json_prolog, you will see four new services in your ROS ecosystem:

$ rosservice list
/json_prolog/finish
/json_prolog/next_solution
/json_prolog/query
/json_prolog/simple_query

You can query these services using plain roslisp.

cram_json_prolog adds syntactic sugar to these raw service calls, e.g., by maintaining a persistent service client, having a lazy list representation of possibly infinite solutions of the Prolog query etc. To use cram_json_prolog you need to git clone another two repos: cram_core and cram_3rdparty, as they are dependencies of cram_json_prolog. So you have a choice: have 3 extra repos in your workspace and use the presumably simpler interface vs. get by without syntactic sugar. I'd suggest you first fiddle around with raw service calls and use the code in cram_json_prolog only as reference / examples.