Term Entity-relationship Model (E-R Model)Definition A logical representation of the data for an organization or for a business area, using entities for categories of data and relationships for associations between entities.Term Entity-relationship Diagram (E-R Diagram, or ERD)Definition A graphical representation of an entity-relationship model.Term Definition A statement that defines or constrains some aspect of the business. It is intended to assert business structure or to control or influence the behavior of the business.Term Definition A person, a place, an object, an event, or a concept in the user environment about which the organization wishes to maintain dataTerm Definition A collection of entities that share common properties or characteristics.Term Definition A single occurrence of an entity type.Term Definition An entity that exists independently of other entity types.Term Definition An entity type whose existence depends on some other entity type.Term Definition The entity type on which the weak entity type depends.Term Definition The relationship between a weak entity type and its owner.Term Definition A property or characteristic of an entity or relationship type that is of interest to the organizationTerm Definition An attribute that must have a value for every entity (or relationship) instance with which it is associated.Term Definition An attribute that may not have a value for every entity (or relationship) instance with which it is associated.Term Definition An attribute that has meaningful component parts (attributes).Term Simple (or Atomic) AttributeDefinition An attributes that cannot be broken down into smaller components that are meaningful to the organization.Term Definition An attribute that may take on more than one value for a given entity (or relationship) instance.Term Definition An attribute whose values can be calculated from related attribute values.Term Definition An attribute (or combination of attributes) whose value distinguishes instances of an entity type.Term Definition An identifier that consists of a composite attribute.Term Definition A meaningful association between (or among) entity types.Term Definition An association between (or among) entity instances where each relationship instance associates exactly one entity instance from each participating entity type.Term Definition An entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances.Term Definition The number of entity types that participate in the relationship.Term Definition A relationship between instances of a single entity type.Term Definition A relationship between the instance of two entity types.Term Definition The simultaneous relationship among the instances of three entity types.Term Definition A rule that specifies the number of instances of one entity that can (or must) be associated with each instance of another entity.Term Definition The minimum number of instances of one entity that may be associated with each instance of another entity.Term Definition The maximum number of instances of one entity that may be associated with each instance of another entity.Term Definition A time value that is associated with a data value, often indicating when some event occurred that affected the data value. Business rule: A statement that defines or constrains some aspect of the business. It is intended to assert business structure or to control or influence the behavior of the business. Show
Term: A word or phase that has a specific meaning for the business. Fact: An association between two or more terms. Entity-relationship model (E-R model): A logical representation of the data for an organization or for a business area. Entity-relationship diagram (E-R diagram): A graphical representation of an entity-relationship model. Entity: A person, place, object, event or concept in the user environment about which the organization wishes to maintain data. Entity type: A collection of entities that share common properties or characteristics. Entity instance: A single occurrence of an entity type. Strong entity type: An entity that exists independently of other entity types. Weak entity type: An entity whose existence depends on some other entity type. Identifying owner: The entity type on which the weak entity type depends. Identifying relationship: The relationship between a weak entity type and its owner. Attribute: A property or characteristic of an entity type that is of interest to the organization. Composite attribute: An attribute that can be broken down into component parts. Simple attribute: An attribute that cannot be broken down into smaller components. Multivalued Attribute: An attribute that may take on more than one value for a given entity instance. Derived attribute: An attribute whose values can be calculated from related attribute values. Identifiers: An attribute (or combination of attributes) that uniquely identifies individual instances of an entity type. Composite Identifiers: An identifier that consists of a composite attribute . Relationship types : A meaningful association between (or among) entity types. Relationship instance : An association between (or among) entity instances where each relationship instance includes exactly one entity from each participation entity type. Associative entity: An entity type that associates the instance of one or more entity types and contains attributes that are particular to the relationship between those entity instances. Degree: The number of entity types that participate in a relationship. Degree -> Unary relationship : A relationship between the instance of a single entity type. Degree -> Binary relationship : A relationship between the instances of two entity types. Degree -> Ternary relationship : A relationship between the instances of three entity types. Cardinality constraint : Specifies the number of instances of one entity that can (or must) be associated with each instance of another entity. Minimum Cardinality: The minimum number of instances of one entity that may be associated with each instance of another entity. Maximum Cardinality: The maximum number of instances of one entity that may be associated with each instance of another entity. Time stamp : A time value that is associated with a data value. Questions from Companion WebsiteMultiple Choice1. The E-R model is most often used as a tool during the ___ phase of database development. 2. Good business rules are 3. A good data name should be 4. Which is NOT included in the definition of an entity? 5. Which is NOT an example of a strong entity type? 6. A property or characteristic of an entity type is a(n) 7. If EMPLOYEE is the entity type, then SMITH, JOHN is the entity ____. 8. An attribute whose value can be calculated from related attribute values is a(n) ___ attribute. 9. An attribute that can be broken down into component parts is a ____ attribute. 10. A meaningful association between entity types is a(n) 11. The most common type of relationship encountered in data modeling is the ____ relationship. 12. The _______ specifies the number of instances of one entity that can (or must) be associated with each instance of another entity. 13. An example of a good relationship name is 14. Which is NOT a basic construct of an E-R model? 15. An example of a multivalued attribute might be True/False Questions1. The E-R model was introduced in an article by Chen in the 1980s. 2. Business rules should be determined primarily by interviewing executives in the business. 3. Data names should relate to business but not be overly technical. 4. Diagrams are not usually used for data definitions. 5. An E-R diagram consists of entities and resources. 6. There is no standard notation for an E-R diagram. 7. A strong entity type does not need an identifier. 8. STUDENT_REGISTRATION_FOR_CLASS is a good entity type name. 9. A cardinality constraint specifies the maximum number of attributes an entity may have. 10. An entity can have only one defined attribute. 11. A multivalued attribute is an attribute that is common to many entities. 12. A relationship is an association between attributes. 13. The degree of a relationship is the number of entity types that participate in a relationship. 14. A ternary relationship is a simultaneous relationship between more than three entity types. 15. A time stamp is a time that is saved whenever the database is opened. Essay Questions1. Why is the E-R model so popular? 2. Why is data modeling often considered the most important part of the systems development process? The characteristics of the data, and the facts and rules are essential for ensuring data integrity. Data, not processes, are the most complex aspects of many information systems and require a central role in structuring system requirements. Data tend to be more stable than the business processes, so an information system based on data will be useful for a longer period of time. What is the entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances?Ordinary I. An entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances. A named property or characteristic of an entity that is of interest to the organization.
Is an association between the instances of one or more entity types?44) An aggregation is an association between the instances of one or more entity types that is of interest to the organization.
What is an association entity type?An associative entity is a term used in relational and entity–relationship theory. A relational database requires the implementation of a base relation (or base table) to resolve many-to-many relationships. A base relation representing this kind of entity is called, informally, an associative table.
Which of the following is an instance of an entity type?Answer: An entity type is a collection of entities that share common properties. An entity instance is a single occurrence of an entity type. So, for example, STUDENT is an entity type and John Smith is an entity instance. How is a strong entity different from a weak entity?
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