The entity-attribute-value model allows for a restricted set of attributes to be attached to an entity, reducing unused data variables and allowing for easy addition of new attributes. It provides flexibility in data modeling and can be used alongside traditional relational structures. Metadata is necessary for effective implementation.
An entity-attribute-value model is a method of representing a collection of data within a computer. The model is designed to allow an entity to be described by a restricted set of attributes selected from a larger list of possible attributes. By indexing the largest list of attributes, only relevant information can be attached to the data structure of the entity. This approach allows a program or database to maintain a dynamic list of all possible attributes that can grow as needed while maintaining the integrity of the already recorded data.
One way for a person to visualize the entity-attribute-value model is to imagine a personal address book in relation to a complete telephone directory. The address book lists each person in an area. A personal address book lists only those people in the address book who are relevant to the owner. It would be inefficient to carry a personal address book that lists thousands of unknown people, so the personal address book only contains people who are relevant to the owner. In this example, the names of the people in the address book are the attributes and their phone numbers are the values of those attributes.
This approach to creating databases or other types of information management software has many advantages. All possible attributes are stored in a single list, so each record doesn’t have to have a large amount of unused data variables or fields. This reduces the size of archived records. It also keeps the information attached to an entity relevant and concise so that you don’t have to traverse through hundreds of empty attribute fields to see fields with a value. New attributes can be easily added without the need for a full database conversion or even changes to existing records.
Another advantage of using the entity-attribute-value model is that the attributes in the list need not all be of the same data type. Not only can each attribute be a different data type, but in object-oriented programming, they can be entirely different classes of program. This provides great flexibility in designing a database that relies on this form of data modeling.
The entity-attribute-value model is not a unique data model. In most databases, traditional relational structures can also be used to represent data where it is more practical to do so. The surrounding data record can be managed relationally while fields internals are managed with the entity-attribute-value model.
A database or program that uses the entity-attribute-value model of data modeling will most likely need to use metadata. Metadata is a collection of rules and guidelines that bridge the gap between the user and the data. It can define what values are valid for a given attribute, how the value should be displayed and possibly also how the attributes could be organized during report generation. Without the implementation of metadata, the model entity-attribute value can become a inflexible and cumbersome database structure.
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