text: The Semantic Web Rule Language (SWRL) was created because there are certain kinds of inferences that 
  can’t be done by Description Logic (DL) axioms. Also, in my experience there are also times where an 
  inference can be done using DL, but it can be more intuitive to define that inference as a rule. 
  
  There are actually two UI’s for SWRL in Protégé. There is the SWRL tab and there is also a Rules view 
  that can be added to the UI as we added a view in section 8.2. The SWRL tab is the one that is being more 
  actively developed and I recommend you always use that. This chapter will focus on the SWRL tab. 
  Everything in this chapter applies to the SWRL tab and will be slightly different in the Rules view. For an 
  overview of the Rules view see the SWRL Process Modeling tutorial listed at the end of this chapter. 
  
  Like all rule systems, SWRL consists of a left-hand side (called the antecedent) and a right-hand side 
  (called the consequent). The two are separated by an arrow created with a dash and a greater than 
  character like this: ->. Each expression in a SWRL rule is separated by a ^ sign. The consequent of the 
  rule fires if and only if*every*expression in the antecedent is satisfied. Since the antecedent can be 
  satisfied multiple times, this means that SWRL rules can do iteration. They will fire for every 
  combination of values that can satisfy the antecedent. All parameters (variables that are wildcards and get 
  bound dynamically as the rule fires) are preceded by a ?. 