Why entity data model

DataModel : In order to solve a problem, objects interact with each other. Some objects share a relationship among them and consequently, form a data model that represents the objects and the relationship between them. In an application managing customer orders, for instance, if we have a customer and order object then these objects share a many to many relationship between them.

The data model is eventually dependent on the way our objects interact with each other. In a database, we see the data model as a network of tables referring to some other tables. To know more about object relationships visit my blog post: Basics of Object Relationships. Adding relationships between entities creates a "data model". Next step is to normalise it to ensure it meets "normal form".

In ERD terms, you may have "logical" and "physical" models. The logical describes the data-model in simple high-level terms that witholds the technical detail required to implement it. It represents the system solution overview. The physical model includes technical details required to actually implement the system such as "many-to-many join tables" needed to implement "many-to-many" relationships. I'm not quite sure what you mean by "model" and "view model" in a related context.

Here, a model is some data component and the view represents an observer of that data such as a table or graph UI component. There's lots on-line explaining "model view controller" or "MVC". This representation will be mapped to a table in a database and its attributes will be transformed into columns. An entity is written using a POCO class that is a simple class, as you can see in the following example in C :.

Working with UI creation is a complex task. To keep things organized, programmers separate their applications into layers. Each layer is responsible for a task and this prevents the code from being messed up. Within the MVC we have a layer responsible for representing the data previously stored, a given could be an instance of a person modeled in the previous example.

This layer is the Model. This template will be used to construct the view. However a ViewModel is a simplified representation of the data with only the information that is required for the construction of a view. It is simply an abstract model this model is different from the MVC layer model which establishes the relationships that exist between the elements that represent real-world entities.

It is a very comprehensive subject. First of all,to know about Entity you must know about Class. All of them represent same fields but the terminology changes based on declaration. Association instances are logically grouped in an association set.

Association sets and entity sets are logically grouped in an entity container. Entity types contain properties that define their structure and characteristics. Properties in a conceptual model are analogous to properties defined on a class in a computer program. In the same way that properties on a class define the shape of the class and carry information about objects, properties in a conceptual model define the shape of an entity type and carry information about entity type instances. A property can contain primitive data such as a string, an integer, or a Boolean value , or structured data such as a complex type.

A conceptual model is a specific representation of the structure of some data as entities and relationships. One way to represent a conceptual model is with a diagram. The following diagram represents a conceptual model with three entity types Book , Publisher , and Author and two associations PublishedBy and WrittenBy :.

This representation, however, has some shortcomings when it comes to conveying some details about the model. For example, property type and entity set information are not conveyed in the diagram. The richness of a conceptual model can be conveyed more clearly with a domain-specific language DSL. The ADO. The following is the CSDL definition of the conceptual model in the diagram above:. Every association has two association ends that specify the entity types involved in the association.

Each association end also specifies an association end multiplicity that indicates the number of entities that can be at that end of the association. Entities at one end of an association can be accessed through navigation properties, or through foreign keys if they are exposed on an entity type. Entity types contain properties that define their structure and characteristics.

For example, a Student entity type may have properties such as Student Id, Name etc. A property can contain primitive data such as a string, an integer, or a Boolean value , or structured data such as a complex type.

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