Designing the data storage architecture is an important activity in system design. There are two main types of data storage formats： files and databases. Files are electronic of data that have been optimized to perform a particular transaction. There are several types of files that differ in the way they are used to support an application. （ ） store core information that is important to the business and , more specifically , to the application , such as order information or customer mailing information. （ ） contain static values , such as a list of valid codes or the names of cities . Typically, the list is used for validation. A database is a collection of groupings of information that are related to each other in some way. There are many different types of databases that exist on the market today. （ ） is given to those databases which are based on older , sometimes outdated technology that is seldom used to develop new applications . （ ） are collections of records that are related to each other through pointers In relational database , （请作答此空） can be used in ensuring that values linking the tables together through the primary and foreign keys are valid and correctly synchronized.