Is an entity type that is meaningful to the organization and that shares common attributes or relationships distinct from other sub groupings?

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A detailed model that captures the overall structure of organizational data that is independent of any database management system or other implementation considerations. Independent of any database management system (DBMS) or other implementation considerations.

Conceptual Data Modeling Process

- Develop a data model for the current system. - Develop a new conceptual data model that includes all requirements of the new system. - In the design stage, the conceptual data model is translated into a physical design. - Project repository links all design and data modeling steps performed during SDLC.

1. Planning - Enterprise wide data model (E-R with only entities)/Conceptual data model (E-R with only entities for specific project) 2. Analysis - Conceptual data models (E-R attributes) 3. Design - Logical data model (relational) and physical file and database design (file organizations) 4. Implementation - Database and file definitions 5. Maintenance - Data model evolution

Entity-relationship Data Model (E-R Model)

A detailed, logical representation of the entities, associations, and data elements for an organizational or business area. It is expressed in terms of: Data entities in the business environment, Relationships or associations among those entities, and Attributes or properties of both the entities and their relationships.

Entity-relationship Diagram (E-R Diagram)

A graphical representation of an E-R model. 

A person, place, object, event or concept in the user environment about which data is to be maintained. 

Entity Type (entity class)

Collection of entities that share common properties or characteristics. Each of these are given a name because the name represents a class or set, it is singular. 

Single occurrence of an entity type.

- A singular noun. - Descriptive and specific to the organization. - Concise. - Should be named for the result of the vent, not the activity or process of the event.

An entity type definition should:

- Include a statement of what the unique characteristic(s) is (are) for each instance. - Make clear what entity instances are included and not included in the entity type. - Often include a description of when an instance of the entity type is created or deleted.

For some entity types the definition must specify:

- When an instance might change into an instance of another entity type. - What history is to be kept about entity instances.

A named property or a characteristic of an entity that is of interest to the organization. EX: Student_ID, Student_Name, Home_address, Phone_Number, Major

- Attribute name is a noun and should be unique. - Make it unique for clarity, each attribute name should follow a standard format. - Similar attributes of different entity types should use similar but distinguishing names.

- States what the attribute is and possibly why it is important. - Should make it clear what is included and what is not included. - Contain any aliases/alternative names. - States the source of values for the attribute. - If a value for the attribute is required/optional. - If a value for the attribute may change. - Any relationships that attribute has with other attributes.

An attribute (for combination of attributes) that uniquely identifies each instance of an entity type. EX: Student_ID for a STUDENT entity type.

A candidate key that has been selected as the unique, identifying characteristic for an entity type. 

Selection rules for an identifier:

- Choose a candidate key that will not change its value. - Choose a candidate key that will never be null. - Avoid using intelligent keys. - Consider substituting single value surrogate keys for large composite keys.

An attribute that may take on more than one value for each entity instance.EX: Skill is one of the attributes of EMPLOYEE. If each employee can have more than one skill, Skill is considered this type of attribute. It is enclosed in curly brackets { }.

A set of two or more multivalued attributes that are logically related. 

An attribute that must have a value for every entity instance.

An attribute that may not have a value for every entity instance. (Date_of_Birth/Employee_Age)

An attribute that has meaningful component parts. EX: Employee_Name (First_Name, Last_Name as atomic components)

An attribute whose value can be computed from related attribute values. EX: Employee_Age (derived from today's date and Date_of_Birth)

An association between the instance of one or more entity types that is of interest to the organization. An association usually means that an event has occurred or that there ecists some natural linkage between entity instances and for this reason, they are labeled with verb phrases. EX: "Completes" between EMPLOYEE and COURSE entity types.

The number of entity types that participate in relationship. EX: There are two of these in the EMPLOYEE and COURSE figure.

Unary Relationship (Recursive Relationship)

A relationship between instances of one entity type. EX: Is_married_to shows a one-to-one relationship between instances of the PERSON entity type. That is, each person may be currently married to one other person.

A relationship between instances of two entity types. This is the most common type of relationship encountered in data modeling. 

A simultaneous relationship among instance of three entity types. Not the same as binary relationships. 

The number of instances of entity B that can (or must) be associated with each instance of entity A. Minimum - The minimum number of instances of entity B that may be associated with each instance of entity A. Maximum - The maximum number of instances of entity B that may be associated with each instance of entity A. 

Mandatory vs. Optional Cardinalities

Specifies whether an instance must exist or can be absent in the relationship.

- It is a verb phrase (EX: Assigned_to, Supplies, or Teaches). They represent actions, usually in the present tense. It states the action taken, not the result of the action (EX: Assigned_to, not Assignment). - Avoid vague names, such as Has or Is_related_to. Use descriptive verb phrases taken from the action verbs found in definition of the relationship.

- Explain what action is to be taken and why is it important. - Give examples to clarify the action. - Explain any optional participation. - Explain the reason for any explicit max. cardinality other than many. - Explain any restrictions on participation in the relationship. - Explain the extent of history that is kept in the relationship. - Explain whether an entity instance is involved in a relationship instance can transfer participation to another relationship instance.

Associative Entity (Gerund)

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. The data modeler chooses to model the relationship as an entity type.

A subgrouping of the entities in an entity type. It is meaningful to the organization and shares common attributes or relationships distinct from other subgroupings. EX: STUDENT is an entity type in a university. Two things that would represent this is are GRADUATE STUDENT and UNDERGRAD STUDENT. 

A generic entity type that has a relationship with one or more subtypes. EX: PATIENT is connected with a line to circle, which in tern is connected by a line to each of the two subtypes, OUTPATIENT and RESIDENT PATIENT. 

Total Specialization Rule

Specifies that each entity instance of the supertype must be a member of some subtype of the relationship.

Partial Specialization Rule

Specifies that an entity instance of the supertype does not have to belong to any subtype. 

Specifies that if an entity instance of the supertype is a member of one subtype, it cannot simultaneously be a member of any other subtype.

Specifies that an entity instance can simultaneously be a member of two or more subtypes.

Specifications that preserve the intergrity of the logical data model. 

Four types of business rules:

1. Entity integrity: unique, non-null identifiers 2. Referential integrity constraints: rules governing relationships between entity types 3. Domains: constraints on valid values for attributes 4. Triggering operations: other business rules that protect the validity of attribute values

The set of all data types and values that an attribute can assume. Some advantages include: verifying that the values for an attribute are valid, ensures that various data manipulation operations are logical, and help conserve effort in describing attribute characteristics.

An assertion or rule that governs the validity of data manipulation operations such as insert, update, and delete. 

Triggering operation includes:

1. User rule - a concise statement of the business rule to be enforced by the triggering op. 2. Event - the data implementation operation (insert, delete, or update) that initiates op. 3. Entity name - The name of the entity being accessed and/or modified. 4. Condition - The condition that causes the operation to be triggered. 5. Action - The action taken when the operation is triggered.

Packaged Data Models - Universal Data Models

Templates for one or more core subject areas (customers, products, accounts, documents) and/or core business functions (purchasing, accounting, receiving, project management).

Packaged Data Models - Industry Specific Data Models

This is designed to be used by organizations within specific industries. These models are based on the premise that data model patterns for organizations are similar within a particular industry. 

Benefits of Database Patterns and Packaged Data Models

- Validated, cost reduction, anticipate the future, facilitates systems analysis, and consistent and complete. - Dramatically reduced implementation times and costs - provides a starting point for asking requirements questions. - Higher-quality models - represents "best practice" data modeling techniques and data model components whose quality often exceeds that which can be achieved by internal development teams, given typical organizational pressures.

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?

What is a subtype entity?

What are the attributes of each entity?

What is the term that refers to the number of instance of entity from a relation that can be associated with the relation?