Acceleo and Capella Query Language

Hello everyone,
I was asking if there is a specific document or a link to learn the language on how to query the the model using Acceleo.

have a look to Capella Eclipse Help, all sections in Capella Guide > User Manual > Model Analysis > Model Queries
Best regards,

To complete Michel’s answer.
Acceleo 3 is an implementation of the Object Management Group (OMG) MOF Model to Text Language (MTL) standard. So the ‘language’ is MTL. The documentation is available here:
See also
Acceleo Operations Reference and
OCL Operations Reference
Note for an usage with Capella, there is some tips in the thread below sg_2203
Be careful not to confuse with
AQL (Acceleo Query Language), a slightly different language, used in many others Capella related components (for example in the interpreter view).

Thanks for your answer. Sorry for asking again but I am new to this, so I want to make sure.
I used a sample code that was provided in this thread: ;goto=2169
I was able to output a template using this code.
My question is what is the language used in this part AQL or MTL?

Your sample is in Acceleo 3 (MTL)