Basic Terminology: E/R, RA, Database, File Systems

Question 1

What are three other names for row?

Answer 1

• occurrence, example (E/R modeling)
• record (file systems)
• tuple (relational algebra)

Question 2

What is a domain?

Answer 2

• a “vertical part” in a relation (relational algebra term)
• aka column / attribute / field

Question 3

What is a record?

Answer 3

• a “horizontal part” of a file (file system term)
• aka row / occurrence, example / tuple

Question 4

What is a database?

Answer 4

• a collection of related data
• represents some aspect of the real world (miniworld)
• a logically coherent collection with some inherent meaning
• designed, built, populated with data for a specific purpose, with intended users and applications of interest

Question 5

What is the schema of a database?

Answer 5

• the skeleton structure that represents the logical grouping of the entire database
• defines a database’s entities and the relationships among them
• a set of formulas (sentences) called integrity constraints imposed on a database
• specified during design, not expected to change often

Question 6

What is a file?

Answer 6

• aka table / relation / entity
• file system term for “the whole thing”

Question 7

What are three other names for column?

Answer 7

• attribute (E/R modeling)
• field (file systems)
• domain (relational algebra)

Question 8

What is an entity?

Answer 8

• “the whole thing” in E/R Modeling
• aka table / file / relation
• represents a real-world object or concept (e.g., employee or project)

Question 9

What is an attribute?

Answer 9

• a “vertical part” in an entity in E/R Modeling
• aka column / domain / field
• represents some property of interest that further describes an entity (e.g., employee’s name or salary)

Question 10

What is a relation?

Answer 10

• “the whole thing” in relational algebra terms
• aka table / entity / file

Question 11

What is a tuple?

Answer 11

• a “horizontal part” in a relation (relational algebra term)
• aka row / occurrence, example / record

Question 12

What is the relational data model?

Answer 12

• data model which represents a database as a collection of tables, where each table can be stored as a separate file
• all data is represented in terms of tuples, grouped into relations

Question 13

What are three other names for table?

Answer 13

• entity (E/R modeling)
• file (file systems)
• relation (relational algebra)

Question 14

What is an occurrence or example?

Answer 14

• a “horizontal part” of an entity in the E/R Model
• aka row / tuple / record

Question 15

What is data?

Answer 15

known facts that can be recorded and that have implicit meaning

Question 16

What is a field?

Answer 16

• a “vertical part” of a file (file system term)
• aka column / attribute / domain

Question 17

How do you state a “relationship sentence”?

• give a template sentence for a relationship between 2 entities
• state what options you have (crossbar, arrowhead)

Answer 17

Each __(entity)__ must be / may be __(relationship)__ one or more / one and only one __(entity)__.

• must be (if there’s a cross bar)
• *may be** (no cross bar)
• one or more (if there’s an arrowhead/branch)
• *one and only one** (otherwise)