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Flashcards in Information Management Deck (23)
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What is data versus information and true belief?

Data | 52 --- Structured representation (encoding) Information | J Smith's final score is 52% --- Data + Meaning Knowledge | I've passed! --- True belief


For managing data, what features must the storage tool provide?

Data definition, Data entry, Data editing, Querying and persistence (data existing beyond a single operation or program invocation


What is a database?

Is an entity in which data can be stored in a structured manner, with as little redundancy as possible. It is viewable by many users at the same time (controlled concurrent access.)


Main difference of a Local Database?

Can be used on one machine by one user only


Main difference of a Distributed Database?

The information is stored on remote machines and can be accessed over a network.


What is a DBMS?

Is a suite of services (software applications) for managing databases, which involves: - Enabling simple access to data - Allowing multiple users access to the information - Manipulating the data found in the database (inserting, deleting, editing)


Data bases avoid redundancy because?

Ambiguity - Same thing with different name in different files. Inconsistency - If data changes in one place it should also change in the other files it exists in. Wasted Effort - Should share data where possible to save time and effort


What are the five stages of a database design lifecycle?

Requirements Analysis, Conceptual Design, Logical Design, Schema Refinement, Physical Design/Tuning


Creating a database involves?

Capturing user requirements Representing them in a MODEL Converting model into a SCHEMA Implementation on a DBMS


When designing a database, How can you identify User requirements?

Talk to client (CEO of company etc) Talk to customers (End users, those who might view) Talk to different levels of users (admin, programmers etc)


When designing a database, How can you identify Data requirements?

Write down all the different 'Things' that you need to store data about. Take not e of any relationships between the things talked about.


Describe High Level Conceptual Data Models

They describe data in a manner close to there real world(external) meaning - as entity types, attributes and relationships.


Describe Implementation-Level Logical Data Models

High level conceptual model can be converted into conceptual schema describing how the data is stored - as tables and records, for instance.


Describe Low-Level or Physical Data Models

Low- Level or Physical Data Models describe how data is stored on the computer: files, storage structures etc.


What is a Relational Model?

Information is represented by a collection of two dimensional tables with rows and columns


What is a Network Model?

Information is represented as a tree of records organised in sets connected by ownership links


What is an Object Oriented Model?

Collections of 'classes' with certain 'behaviours'/methods


For Referential Integrity, What does Restrict do?

Ban any alterations to a primary key if there are foreign key references to it.


For Referential Integrity, What does Cascade do?

Cascade the effect to all relations in all tables that refer to it.


For Referential Integrity, What does the option 'Set to NULL' do?

Allow update in original table to set all corresponding FK values to NULL.


Two sets are equal if and only if they?

Have the same elements. Order does NOT matter, Repetition does NOT matter.


Sets usually group together items with?

Similar properties


What is a power set?

The set of all the subsets of a given set