A conceptual schema is a collection of conceptual diagrams that define views of the domain. Concepts and links may be shared between diagrams. A conceptual schema should include enough diagrams to show all the links that a concept may have and the various configurations in which the links may occur, but it is not necessary to show each state in the concept's lifecycle. For example, a marker allele may have a name and a frequency in a certain population, or it may have a size and a frequency in a certain population, but alleles do not typically have both names and sizes. When the database is developed, there may be a user view which corresponds exactly to a single (or a few) conceptual diagrams.