A great amount of research papers stated that there are clinical data captured in narrative texts (e.g. clinical notes, discharge letters), and proposed techniques/methods to transform such unstructured information into structured data that could be used for the secondary use.. However, little research has been conducted to answer questions about the data itself in the first place:

• What are the unstructured clinical data captured in hospitals?
• Why such data is captured in free-text?
• Are there any difference of unstructured clinical data among hospitals?
• How to quantitatively measure how unstructured these data is or how difficulty it is to process them?
• etc.

In many cases, researchers or practitioners just skip such questions and move directly to develop tools to transform unstructured data into structured information. We believe a better understanding of such data will provide useful insights for developing data transformation tools or improve the efficiency and effectiveness of such existing tools in practice.