public static bool HasSubSetOf(this List <AttributeList> list, AttributeList attrs)
{
foreach (var a in list)
{
if (attrs.Contains(a) && a.Count < attrs.Count)
{
return(true);
}
}
return(false);
}
public bool Contains(AttributeList attrList)
{
foreach (var a in attrList.attributes)
{
if (!attributes.Contains(a))
{
return(false);
}
}
return(true);
}
public static bool HasSupersetOf(this List <AttributeList> list, AttributeList attrs)
{
foreach (var a in list)
{
if (a.IsSupersetOf(attrs))
{
return(true);
}
}
return(false);
}
public bool IsSupersetOf(AttributeList other)
{
if (other.Count > Count)
{
return(false);
}
for (var i = 0; i < other.Count; i++)
{
if (attributes[i] != other[i])
{
return(false);
}
}
return(true);
}
public static List <AttributeList> FindKeys(AttributeList relation, List <FunctionalDependency> fdList)
{
var superKeys = FindSuperKeys(relation, fdList);
var result = new List <AttributeList>();
foreach (var superKey in superKeys)
{
if (!superKeys.HasSubSetOf(superKey))
{
result.Add(superKey);
}
}
return(result);
}
public static List <AttributeList> FindSuperKeys(
AttributeList relation, List <FunctionalDependency> fdList)
{
var result = new List <AttributeList>();
var combinations = GetCombinations(relation);
foreach (var attrList in combinations)
{
var closure = ComputeClosure(attrList, fdList);
if (closure.Count >= relation.Count)
{
result.Add(attrList);
}
}
return(result);
}
public static AttributeList ComputeClosure(
AttributeList attr, List <FunctionalDependency> fdList)
{
var size = 0;
var result = new AttributeList(attr);
do
{
size = result.Count;
foreach (var fd in fdList)
{
if (result.Contains(fd.LeftHandSide))
{
result.Add(fd.RightHandSide);
}
}
} while (size != result.Count);
return(result);
}
public static List <AttributeList> GetCombinations(AttributeList list)
{
var result = new List <AttributeList>();
var count = (int)Math.Pow(2, list.Count);
for (var i = 1; i <= count - 1; i++)
{
string str = Convert.ToString(i, 2).PadLeft(list.Count, '0');
var combi = new AttributeList();
for (var j = 0; j < str.Length; j++)
{
if (str[j] == '1')
{
combi.Add(list[j]);
}
}
result.Add(combi);
}
return(result);
}
public static void Main(string[] args)
{
Console.WriteLine("Exercise_2_1_1\n");
var relation = new AttributeList("A,B,C,G,H,I");
Console.WriteLine($"Relation: {relation}");
Console.WriteLine();
//test 2
var fdList = new List <FunctionalDependency>()
{
new FunctionalDependency("A", "B"),
new FunctionalDependency("A", "C"),
new FunctionalDependency("C G", "H"),
new FunctionalDependency("C G", "I"),
new FunctionalDependency("B", "H")
};
Console.WriteLine("Functional dependencies:");
fdList.Print();
Console.WriteLine();
var keys = AttributeClosure.FindKeys(relation, fdList);
Console.WriteLine("Keys:");
foreach (var key in keys)
{
Console.WriteLine(key);
}
Console.WriteLine();
var superkeys = AttributeClosure.FindSuperKeys(relation, fdList);
Console.WriteLine("Superkeys:");
foreach (var key in superkeys)
{
Console.WriteLine(key);
}
}
public AttributeList(AttributeList attrList)
{
attributes = new List <string>(attrList.attributes);
}