Data is always an issue to someone. Big data is a new issue because it is 'big', by which I mean no only the size, but the variety of sources, types, complexities and so on. For example, in healthcare domain, we collect data about people, medicines, food, environment and so on. In any of these aspects, there could be a lot of sub-domains we are interested in.
issue 1: collection
What should we collect? we can collect what we selected or what exist.
How to collect? it is a challenge trying to collect big data about large population for a long period
issue 2: cleansing
issue 3: integration
