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16 Cards in this Set
- Front
- Back
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describe a data model |
data models embody a set of concepts to describe a database. |
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How do you distinguish between a specification of a database and the database itself? |
Schema is equivalant to specification - contains relationships of all entities. intensional database. Instances are a valid state of a database at any one time. extensional database. |
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Name the 5 steps of database application development. |
Problem investigation. Data Modelling Database Design. Database Implementation. Database modelling/tuning. UML Diagrams Conceptual Diagrams DBMS-specific conceptual schema Internal schema and database Optimized database. |
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what are three important things to consider when data modelling? ERC |
1) Entities - what data objects are relevant? 2) Relationships - How are they related? 3) Constraints - What constraints must be satisfied? |
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how would you produce a data model? |
through an entity relationship model. |
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name differences between an ER and an EER? |
EER has subclass and superclasses data is drawn from multiple entities. |
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define a database, database management system and meta data |
database - a collection of related data database management system - provides functionality to access and manage a database meta data - defines what data is stored and how it is structured |
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why do we use database management systems? |
to avoid: 1) redundant data 2) redundant processes 3) data inconsistancy to enable: 1) ease of maintanance 2) sharing of data |
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name 5 characteristics of a DBMS |
1) data is integrated - combining data from different sources and providing a unified view of these data. 2) data is shared - data can be viewed/modified by multiple users 3) data is persistent - not likely to be modified 4) data is self-describing - contains all info to be able to understand it 5) there are multiple views of data |
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what is a database schema |
a model description of how data is stored |
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what is an instance of a database? |
the data stored in a database at a particular time |
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define 3 roles in a DBMS |
1) database designer identify data to be stored, structure to be used and constraints. 2) database administrator manages/oversee the database's resources, authorisations and security 3) application programmer develop and implement user requirements |
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define a data model |
a data model is an abstract model which organizes elements of data and standardizes how they relate to each other. |
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what are the three types of data model |
1) conceptual high level requirements of the user through classes, relationships and business rules 2) representational adds attributes to conceptual and their heirachy 3) low level table names, formats, data types like a class diagram of a database |
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what are the 5 things to consider when data modelling? |
1) what data objects are relevant (classes) 2) the attributes of each object 3) relations between objects - associations 4) the hierachy of super and sub types - inheritance 5) what constraints must be satisfied |
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what is an entity relationship model |
a model to show data objects and the relationships between them |
