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Service call failed in json-prolog while querying an owl file in Cram

asked 2017-09-13 09:47:17 -0600

aAsoodeh gravatar image

updated 2017-09-13 12:49:31 -0600

jayess gravatar image


I started a roslisp node in cram and have json-prolog query services (i can see


when i do "rosservice list").

Also by typing (json-prolog:check-connection) i receive T. so i assume that everything set up properly.

problem is when i try any query like

(json-prolog:prolog '("rdf_has" ?owlname "" ("literal" ?var)))

i receive

Prolog query failed: Got error: The value
           is not of type

also i have

[(JSON-PROLOG) WARN] 1505226166.532: Service call failed. 
[(JSON-PROLOG) WARN] 1505226166.532: Retrying...


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1 Answer

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answered 2017-09-13 10:20:37 -0600

gaya gravatar image


This seems like an error on the KnowRob side. I execute it on my machine and it works fine. I'm using the master branch of KnowRob (on 14.04), the latest commit I have is from 3rd of September. And I'm using the latest version of cram_json_prolog, master branch, last commit was on 26 June. Try prolog-simple or a simpler query in general.

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same error when trying prolog-simple. do you know any cram project that i can use as pattern to build a clear project? any tutorial? Thanks

aAsoodeh gravatar image aAsoodeh  ( 2017-09-13 12:37:12 -0600 )edit

We have a bunch of tutorials. Here is he one that showcases most complex behaviors It runs on the newest CRAM version (0.4.0). Consult the installation page to get the latest version.

gaya gravatar image gaya  ( 2017-09-18 14:09:49 -0600 )edit

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Asked: 2017-09-13 09:47:17 -0600

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Last updated: Sep 13 '17