Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Undeleted > COMP2004 - DB Conceptual modelling > Flashcards

COMP2004 - DB Conceptual modelling Flashcards

0
Q

Entity Relationship Diagram

A

Specify entities in a system along with their relationships

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

Conceptual modelling

A
  • model objects
  • identify;
    Relationships btwn them
    Their cardinality and participation
    Identify strong and weak entities
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Modelling

A
  • objects - from nouns in UML
  • attributes - properties of objects
  • associations - relationships btwn objects
  • cardinality - 1 to many, many to many
  • participation - optional, mandatory
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Weak entities

A

Can only exist in the presence of a strong entity ( composite notation)
so on UPDATE/DELETE CASCADE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Composite notation

A

It is only called composite if the objects it refers to are really its parts, i.e. have no independent existence. For details, see the aggregation section below.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

High level model - Conceptual model

A

Understanding at a high level the different concepts in the system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Middle level model - Logical model

A

Adding details to the data - middle step between the two

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Low level model - physical model

A

how it is implemented in the database

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Functional dependency

A

Constraint btwn two sets of attributes in a relation from a database

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Relation

A

Is a set of tuples where each element is a member of a data domain. Each distinct domain used in the definition of a relation is called an attribute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Relation

A

Attribute
| | | | |
—————————–
Tuple | | | | |
—————————–
| | | | |
—————————–
The whole thing is relation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Deriving tables

A

Objects become tables with the primary key chosen appropriately

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Tuple/ Row

A

A sequence or ordered list of finite length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Column/Attribute

A

Defines properties of an individual

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Relation

A

Table

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Tuple

A

Row

16
Q

Attribute

A

Column

17
Q

Domain/Type

A

Attribute type

Defines how a given item is constrained

18
Q

Schema

A

Defines a structure of a database
Name ({ as })
Degree of relationship is the number of attributes in a table
Known as relation intension

19
Q

Model

A

Structure
Operations
Constraints
Eg relational, semistructure (xml)

20
Q

Relational model

A

Model
Schema
State

21
Q

Super keys

A

Set of attributes which uniquely identify all other attributes
Values for the attributes in a superkey will identify one unique record

22
Q

Candidate key

A

A subset of the super keys which contain the minimal number of attributes to uniquely identify a record

23
Q

Primary key

A

One of the candidate keys which the user has specified will be the unique identifier for a record. Irreducible. Not null
PRIMARY KEY FIELDS ARE IN CAPITAL LETTERS

24
Q

Foreign key

A

Refers to a candidate key in another table

25
Q

Functional dependency

A

Where a subset of attributes A2 is determined by another subset of attributes A1 such that A2 depends on A1.
A1(determinant) ->A2 (dependent)
Means A1 determines A2 or A2 is determined by A1

26
Q

ACID

A

Atomicity
Consistency
Isolation
Durability

27
Q

Atomicity

A

All the operations in the transaction occur or nothing occurs
An operation must start and then run to dinish without being interrupted or stopped along the way. ATOMOS=indivisible

28
Q

Consistency

A

Any transaction will bring the state of the database from one valid state to another (neither state can invalidate any of the defined rules).
Eg. Transaction transferring funds ensures that sum of both accounts is the same before and after.

29
Q

Isolation

A

Events within a transaction are hidden from other transaction running concurrently. Uses synchronisation techniques.
Concurrent operations on the database must leave the system in a state as if they were run sequentially.

30
Q

Durability

A

Once a transaction has been completed and committed it must guarantee these results survive subsequent malfunctions. The user must have a guarantee that what has happened has actually happened.
A change committed to the database must be permanent, regardless of other operations, power failure, crashes etc

31
Q

Structure of a transaction

A

START A TRANSACTION
SQL STATEMENTS
COMMIT = the statements are installed permanently or ROLLBACK - the transaction aborts, database is restored to the original state

32
Q

Two phase locking

A

Is the ensuring that within each transaction all lock actions precede all unlock actions. This ensures that any legal schedule of transactions remains conflict serialisible.

33
Q

Semi structured data

A

Form of structured data that does not have a matching schema. It still has correct tags (is still well fromed) but tags might not be consistent across whole document.

34
Q

Well formed XML

A

Is syntactically correct XML

Conforms to XML spec and can be parsed

35
Q

Valid XML

A

Is gramatically correct for a given grammar.

Valid XML must also be Well Formed XML

36
Q

DTD

A

Document Type Definition

Undeleted (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions