 The usefulness of one conceptualization over another depends largely on construct validity.To address the non-observability of constructs, U.S. federal agencies such as the National Institutes of Health National Cancer Institute has created a construct database termed Grid-Enabled Measures (GEM) to improve construct use and reuse.Concepts that are considered "constructs" by this definition include that which is designated by the symbol ""3"" or the word ""liberty"".