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Designing a logical data model is all about preparing for the physical data design. Whether physical elements end up being a simple database, a complex data warehouse, or some other data store, the ideas behind the logical design remain the same. In this stage of development, try not to gear any design to a specific physical structure. Keep in mind that we are still just planning the system, and decisions about the physical elements have yet to be made. Even though the physical elements have yet to be determined, there is a definite correlation between what we see in the logical model and what will end up being present when the model takes on a physical form. There is almost a one-to-one mapping between the objects in the logical stage of development and similar objects in the physical databases, tables, files, and other physical articles. Although there are many data storage possibilities, the largest percentage of them are databases, the storage mechanism of choice for most systems. Relational databases are databases in which data is organized into related objects. All objects contained in a database are related to one another in some way. Relational databases, based on the paper written by Dr. E.F. Codd in 1970, store sets of data in relations, called tables. The tables are often related to one another through dependencies, but this is not required. In all the time that has passed from then to .NET, modeling relational data structures still remains based on this concept. |