1 files changed, 23 insertions, 1 deletions
diff --git a/src/unitConverter/unit/UnitSystem.java b/src/unitConverter/unit/UnitSystem.java
index 2e3a5d8..ce8c249 100755
--- a/src/unitConverter/unit/UnitSystem.java
+++ b/src/unitConverter/unit/UnitSystem.java
@@ -16,16 +16,38 @@
  */
 package unitConverter.unit;
 
+import java.util.Objects;
+
+import unitConverter.dimension.UnitDimension;
+
 /**
  * A system of units. Each unit should be aware of its system.
  * 
  * @author Adrien Hopkins
  * @since 2018-12-23
+ * @since v0.1.0
  */
 public interface UnitSystem {
 	/**
-	 * @return name of system
+	 * Gets a base unit for this system and the provided dimension.
+	 * 
+	 * @param dimension
+	 *            dimension used by base unit
+	 * @return base unit
+	 * @throws NullPointerException
+	 *             if dimension is null
 	 * @since 2019-01-25
+	 * @since v0.1.0
+	 */
+	default BaseUnit getBaseUnit(final UnitDimension dimension) {
+		Objects.requireNonNull(dimension, "dimension must not be null.");
+		return new BaseUnit(dimension, this);
+	}
+
+	/**
+	 * @return name of system
+	 * @since 2018-12-23
+	 * @since v0.1.0
 	 */
 	String getName();
 }