DB Midterm Exam
Explain the role of System Designers and Implementors
- Design and implement DBMS packages in the form of modules and interfaces, test and debug them. - The DBMS must interface with applications, language compilers, operating system components, etc.
What are the Database System Utilities?
- Loading data stored in files into a database; Includes data conversion tools - Backing up the database periodically on tape - Reorganizing database file structures - Performance monitoring utilities - Report generation utilities - Other functions, including sorting, user monitoring, data compression
What is a relationship set?
- The current set of relationship instances represented in the database - The current state of a relationship type
Explain the self-describing nature of the Database Approach
A DBMS catalog stores the description of a particular database (e.g. data structures, types, and constraints) (meta-data). This allows the DBMS software to work with different database applications.
What is an Entity Type?
A collection of entities with the same basic attributes
What is a Database?
A collection of related data
What is a Schema Construct?
A component of the schema or an object within the schema, e.g., STUDENT, COURSE.
What is a Database Management System?
A data collection program which enables the user to create and maintain the database
What is a Data Model?
A set of concepts to describe the structure of a database, the operations for manipulating these structures, and certain constraints that the database should obey.
What is a Valid (Database) State?
A state that satisfies the structure and constraints of the database.
What are Active and Passive data dictionaries?
Active: is accessed by DBMS software and users/DBA. Passive: is accessed by users/DBA only.
What are the two groups of Users? Explain each.
Actors on the Scene - Those who actually use and control the database content, and those who design, develop and maintain database applications Workers behind the Scene - Those who design and develop the DBMS software and related tools, and the computer systems operators
Explain the Sharing of data and multi-user transaction processing of the Database Approach
Allowing a set of concurrent users to retrieve from and to update the database. Concurrency control with a DBMS guarantees that each transaction is correctly executed or aborted. Recovery subsystems ensures each completed transaction has its effect permanently recorded in the database.
What is the Key attribute of a entity type?
An attribute of an entity type for which each entity must have a unique value. Employee SSN for example
What is a Schema Diagram?
An illustrative display of (most aspects of) a database schema.
How do applications interact with a database? Explain each item by their definition.
By Generating Queries: To access different parts of data and formulate the result of a request or Transactions: may read some data; 'update' certain values or generate new data, and store that in the database
What are the Categories of End Users? Explain what each one does.
Casual - Access the database occasionally when needed Naive or Parametric - Makes of a large section of the end user population which use previously well-defined functions in the form of "canned transactions" against the database. Sophisticated End User - Engineers, Scientists, Business Analysts, and others. They thoroughly familiarize themselves with facilities of the DBMS. Standalone - Has a local/personal copy of the database
What is the Centralized DBMS Architecture?
Combines everything into single system including - DBMS software, hardware, application programs, and user interface processing software. User can still connect through a remote terminal - however, all processing is done at centralized site.
What are the categories of Data Models? Explain each of them.
Conceptual(high level, semantic): Provide concepts that are close to the way many users perceive data. Physical(low level, internal): Provide concepts that describe details of how data is stored in the computer. These are usually specified in an ad-hoc manner through DBMS design and administration manuals. Implementation (representational): Provide concepts that fall between the above two, used by many commercial DBMS implementations (e.g. relational data models used in many commercial systems). Self-Describing: Combine the description of data with the data values. Examples include XML, key-value stores and some NOSQL systems.
When is it OK to not to use a DBMS?
Cost of the DBMS(High cost of Hardware and Overhead for providing the function of the DBMS) When it seems unnecessary(simple and not subject to change/not expecting multi users) When a DBMS is unfeasible When a DBMS will not suffice(Usually stringent real-time requirements)
What are the types of Actors on the Scene?
Database Administrators Database Designers End Users System Analysts and Application Developers
What are the many Functionalities of the DBMS?
Defining Meta-Data Constructing or Loading Manipulating Processing and Sharing Protection or Security Active Processing Presentation and Visualization Maintenance
Explain the role of Tool Developers
Design and implement software systems for modeling and designing databases, performance monitoring, prototyping, test data generation, user interface creation, simulation etc. Facilitate building of applications and allow using database effectively .
What is an Entity Set?
Each entity type will have a collection of entities stored in the database. Is the current state of the entities of that type that are stored in the database.
Explain the Support for Multiple Views of the Database Approach
Each user may see a different view of the database, which describes only the data of interest to that user
What are mini-world entities?
Entities which fit the description within the databases mini-world
State is also called _______
Extension
What is the 3-Tier Client Server Architecture?
Has an intermediate layer in which is the application layer. Common for Web Applications.
What are the types of Database Manipulation Languages(DML)?
High Level or Non-procedural Language: Are "set"-oriented and specify what data to retrieve rather than how to retrieve it. A declarative language. Low Level or Procedural Language: Retrieve data one record-at-a-time; Constructs such as looping are needed to retrieve multiple records, along with positioning pointers.
What are Data Model Operations?
Operations used for specifying database retrievals and updates by referring to the constructs of the data model. These operations may include basic model operation(generic insert, delete, update) and user-defined operations(compute student gpa and update inventory)
When a schema at a lower level is changed, only the _______________ between this schema and higher-level schemas need to be changed in a DBMS that fully supports data independence.
mappings
What are Attributes?
properties used to describe an entity.
What is a Relationship?
relates two or more distinct entities with a specific meaning.
What is a Value Set?
specifies the set of values associated with an attribute
Explain the role of Business Analysts with databases
• Analyze vast amounts of business data and real-time data ('Big Data') for better decision making related to planning, advertising, marketing etc.
What are the Advantages of the Database Approach?
• Controlling redundancy in data storage, in development and maintenance efforts • Sharing of data among multiple users • Restricting unauthorized access to data. Only the DBA staff uses privileged commands and facilities. • Persistent storage for program Objects - Object-oriented DBMSs make program objects persistent • Providing Storage Structures (e.g. indexes) for efficient Query Processing • Optimization of queries for efficient processing • Providing backup and recovery services • Providing multiple interfaces to different classes of users • Representing complex relationships among data • Enforcing integrity constraints on the database • Drawing inferences and actions from the stored data using deductive and active rules/triggers
What are the Type of Actors Behind the Scene?
System Designers and Implementors Tool Developers Operators and Maintenance Personel
Explain Program Data Independence of the Database Approach
The DBMS is the middleman between the programs that use it and the data. It allows changing data structures and storage organization without having to change the DBMS access programs.
What is the Database System?
The DBMS software together with the database. Often applications are included.
What is a Database State?
The actual data stored in a database at a particular moment in time. This includes the collection of all the data in the database. Also known as the database instance(occurance or snapshot).
Explain the Three-Schema Architecture
The architecture used to support (1) use of a catalog to store the database description (schema) so as to make it self-describing, (2) insulation of programs and data (program-data and program-operation independence), and (3) support of multiple user views. It is defined in three levels: Internal, conceptual, and external
What is the difference between a database schema and database state?
The database schema changes infrequently while the database state changes every time the database is updated.
What is a Database Schema?
The description of a database which includes descriptions of the database structure, data types, and the constraints on the database.
What is a mini-world?
The domain of the database
The higher-level schemas themselves are ______________.
Unchanged
Explain the role of System Analysts with databases
Understand the user requirements of naïve and sophisticated users Design applications including canned transactions to meet those requirements.
Database Definition Language(DDL)
Used by the DBA and database designers to specify the conceptual schema of a database.
What are Constructs within Data Models?
Used to define the database structure. Typically include elements(with data types) as well as groups of elements (e.g. entity, record, table), and relationships among such groups
Database Manipulation Language(DML)
Used to specify database retrievals and updates
Explain Data Abstraction of the Database Approach
Usually, a data model is used to hide storage details and present the users with a conceptual view of the database. Programs refer to the data model constructs rather than data storage details
Each attribute has a ____________ associated with it
Value Set
Can an entity type have more than one key?
Yes
Can key attributes be composite?
Yes
What is an Entity?
are specific things or objects in the mini-world that are represented in the database.
What is the many types of cardinality ratios for relationships?
One-to-one One-to-many or Many-to-one Many-to-many
What is OLTIP?
Online Transaction Processing, which allows hundreds of cocurrent transactions to execute per second.
Schema is also called __________
Intention
What is Meta-Data in a Database?
It provides the database definition or description that is stored by the DBMS in the form of a database catalog or dictionary.
What are the different types of data independence? Explain each one.
Logical: The capacity to change the conceptual schema without having to change the external schemas and their associated application programs.(adding data items, changing constraints) Physical: The capacity to change the internal schema without having to change the conceptual schema.(Reorganizing file structures, creating new indexes to improve database performance)
What are the three types of Manipulation in a Database?
Modification - Insertions, deletions, and updates of content Retrieval - Querying, and generating reports Accessing - Through a web application
What are the implications of the Database Approach?
Potential for enforcing standards Reduced application development time Flexibility to change data structures Availability of current information Economies of scale
What is the 2-Tier Client Server Architecture?
Specialized servers with specialized functions
What are Constraints within Data Models?
Specify some restrictions of valid data; these constraints must be enforced at all times.
What is the Initial Database State?
Refers to the database state when it is initially loaded into the system.
What is a relationship type?
Relationships of the same type are grouped or typed into a relationship type - Is the schema description of a relationship - Identifies the relationship name and the participating entity types - Also identifies certain relationship constraints
Explain the Responsibilities of the Database Administrators
Responsible for - authorizing access to the database - coordinating and monitoring database use - Acquiring software and hardware resources, controlling its use and monitoring efficiency of operations
Explain the Responsibilities of the Database Designers
Responsible for - defining the content, the structure, the constraints, and functions or transactions against the database - communicating with the end-users and understand their needs
What are the main characteristics of the Database Approach?
Self-Describing Nature Insulation between programs and data(Program data independence) Data Abstraction: Support for multiple views of data Sharing of data and multi-user transaction processing
What are the types of attributes?
Simple Composite Multi-valued
Explain the role of Operators and Maintenance Personel
They manage the actual running and maintenance of the database system hardware and software environment.
Explain what End Users do?
They use the data for queries, reports and some update the database content.
Explain the role of Application Developers with databases
• Implement the specifications developed by analysts • Test and debug them before deployment.
