Tuesday, July 01, 2014

Entity–Attribute–Value Data Model

Entity–attribute–value model - Wikipedia, the free encyclopedia:

Entity–attribute–value model (EAV) is a data model to describe entities where the number of attributes (properties, parameters) that can be used to describe them is potentially vast, but the number that will actually apply to a given entity is relatively modest. In mathematics, this model is known as a sparse matrix. EAV is also known as object–attribute–value model, vertical database model and open schema.

define:entity - Google Search
a thing with distinct and independent existence.

define:item - Google Search
an individual article or unit, especially one that is part of a list, collection, or set.

define:attribute - Google Search
a quality or feature regarded as a characteristic or inherent part of someone or something.

The Datomic Information Model
For Datomic, that unit is the atomic fact, something we call a Datom.
A Datom has the following components:

  • Entity
  • Attribute
  • Value
  • Transaction (database time)
  • Add/Retract
RDF graphs are sets of subject-predicate-object triples

An RDF graph with two nodes (Subject and Object) and a triple connecting them (Predicate)

BigTable maps two arbitrary string values (row key and column key) and timestamp (hence three-dimensional mapping) into an associated arbitrary byte array. It is not a relational database and can be better defined as a sparse, distributed multi-dimensional sorted map

Key–Value stores use the associative array (also known as a map or dictionary) as their fundamental data model. In this model, data is represented as a collection of key–value pairs, such that each possible key appears at most once in the collection


  • Customer Account—Represented by the entire spreadsheet, it refers to the Amazon Web Services account to which all domains are assigned.
  • Domains—Represented by the domain worksheet tabs at the bottom of the spreadsheet, domains are similar to tables that contain similar data.
    You can execute queries against a domain, but cannot execute queries across different domains.
  • Items—Represented by rows, items represent individual objects that contain one or more attribute name-value pairs.
  • Attributes—Represented by columns, attributes represent categories of data that can be assigned to items.
  • Values—Represented by cells, values represent instances of attributes for items. An attribute can have multiple values.
Comparing Windows Azure Table Storage and Amazon SimpleDB — GauravMantri.com
A “Table” in WATS and a “Domain” in ASDB may look like a table but they are not.
Essentially think of them as a container containing collections of similarname/value pairs representing data.

Each entity (in WATS) and item (in ASDB) consists of one or more attributes. An attribute is a name/value (name/value/data type in WATS) collection

AWS | Amazon DynamoDB | FAQs
The data model for Amazon DynamoDB is as follows:

  • Table: A table is a collection of data items
  • Item: An Item is composed of a primary or composite key and a flexible number of attributes.
  • Attribute: Each attribute associated with a data item is composed of an attribute name and a value or set of values

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