Class: Pho::ResourceHash::SetAlgebra

Inherits:
Object
  • Object
show all
Defined in:
lib/pho/resource_hash.rb

Overview

Class providing set algebra methods over triple hashes

Class Method Summary collapse

Class Method Details

.minus(first, second) ⇒ Object

Accepts two triple hashes, expressed as RDF-in-JSON and returns a new Ruby data structure that constitutes the different between the two graphs

i.e. the return value will be a hash containing the triples that are in the first graph but which are not present in the second.

first

the first graph

second

the second graph.



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# File 'lib/pho/resource_hash.rb', line 20

def SetAlgebra.minus(first, second)
  
  difference = Hash.new        
  first.each do |uri,properties|          
    if second.has_key?(uri)           
      properties.each do |predicate,value|              
        if second[uri].has_key?(predicate)                
          #second hash has same uri and predicate, so check value arrays                
          second_value = second[uri][predicate]
          value.each do |val|
            
            if !object_in_array?(second_value, val)

              difference[uri] ||= Hash.new
              difference[uri][predicate] ||= Array.new
              difference[uri][predicate] << val                      
            end
          end
           
        else                
          #uri is in second, but not this property and value
          difference[uri] ||= Hash.new
          difference[uri][predicate] = value                
        end              
      end
    else
      #uri not in second, so pass all straight-through
      difference[uri] = properties            
    end
    
  end
  
  return difference
  
end

.object_in_array?(array, val) ⇒ Boolean

Is there an object in the specified array, that matches the provided description

Returns:

  • (Boolean) 


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# File 'lib/pho/resource_hash.rb', line 57

def SetAlgebra.object_in_array?(array, val)
  array.each do |entry|

    if entry["type"] == val["type"] 
       if entry["value"] == val["value"]

         if entry["type"] == "literal"
           if entry["datatype"] == val["datatype"] && 
              entry["lang"] = val["lang"]
              return true
           end                     
         end
         return true   
       end
      
    end
  end
  return false
end