Chapter 2 Flashcards
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.
data model
Constructs are used to define the database ______
structure
_________ typically include elements (and their data
types) as well as groups of elements (e.g. entity, record,
table), and relationships among such groups.
constructs
T/F: Constraints specify some restrictions on valid data; these
constraints must be enforced at all times.
true
Operations on the data model may include basic
model operations (e.g. generic insert, delete,
update) and __________ operations (e.g.
compute_student_gpa, update_inventory)
user-defined
T/F: Data model operations are used for specifying database retrievals and updates by referring to the
constructs of the data model.
true
Name 4 Categories of Data Models
- Conceptual (high-level, semantic)
- Physical (low-level, internal)
- Implementation (representational)
- Self-Describing
_____________ data models are also called entity-based or object-based data models.
conceptual (high-level, semantic)
___________ data models provide concepts that are close to the way many users perceive
data.
conceptual (high-level, semantic)
__________ data models provide concepts that describe details of how data is stored in the computer. are usually specified in an ad-hoc manner through DBMS design and administration manuals.
Physical (low-level, internal)
________ data models provide concepts that fall between the high-level and low-level data models, used by many commercial DBMS implementations (e.g. relational data models
used in many commercial systems)
Implementation (representational) data models
___________ data models combine the description of data with the data values. Examples
include XML, key-value stores and some NOSQL systems
self-descibing
___________ is the description of a database. It includes descriptions of the database structure, data types, and the constraints on the database.
Database Schema
_________ is an illustrative display of (most aspects of) a database schema.
Schema Diagram
_____________ is a component of the schema or an object within the schema, e.g., STUDENT, COURSE.
Schema Construct
___________ is the actual data stored in a database at a particular moment in time. This includes the
collection of all the data in the database.
Database State
________ is also called database instance (or occurrence or snapshot).
Database State
T/F: Valid state refers to the content of a database at a moment in time.
false, database state not valid state.
___________ is a state that satisfies the structure and constraints of the database.
valid state
__________ refers to the database state when it is initially loaded into the system.
Initial Database State
T/F: The database schema changes every time the
database is updated.
false, database state not the database schema.
the database schema changes VERY INFREQUENTLY.
________ is also called intension.
Schema
_______ is also called extension.
State
___________ is proposed to support DBMS characteristics of Program-data independence, Support of multiple views of the data, and self-describing nature of DB system. (Not explicitly used in commercial DBMS products,
but has been useful in explaining database
system organization.)
Three-Schema Architecture
Three-Schema Architecture defines DBMS schemas at three levels: ________ schemas, _________ schemas , and ________ schemas.
internal, conceptual, external.
________ schemas are at the external level to describe the various user views. It usually uses the same data model as the conceptual schema.
external
The conceptual schema uses a conceptual or an __________ data model.
implementation
__________ schemas are at the internal level to describe physical storage structures and access paths (e.g indexes). It typically uses a physical data model.
internal
__________ among schema levels are needed to
transform requests and data.
Mappings
T/F: In mappings among schema levels, programs refer to an external schema, and are mapped by the DBMS to the internal schema for
execution.
true.
(Logical/Physical) data independence isthe capacity to change the conceptual schema without having to change the external schemas and their associated application programs.
logical
T/F: Physical data independence is the capacity to change the external schema without having to change the conceptual schema.
false, internal not external.
T/F: Generally, logical data independence exists in
most databases and file environments.
false, physical not logical
When a schema at a lower level is changed, only the ________ between this schema and higherlevel schemas need to be changed in a DBMS
that fully supports data independence. The higher-level schemas themselves are
unchanged. Hence, the application programs need not be changed since they refer to the external schemas.
mappings
Name the 2 DBMS Languages.
- Data Definition Language (DDL)
- Data Manipulation Language (DML)
T/F: High Level or Non-procedural languages must be embedded in a programming language while Low Level or Procedural Languages do not.
false, low level or procedural languages must be embedding in a programming language while high level or non-procedural language can be used in a standalone way or MAY be embedded in a programming language
What are the two types of DML languages?
- High level or non-procedural
- low level or procedural
___________ Langauge is used to specify database retrievals and updates.
Data Manipulation Language (DML)
T/F: DML commands (data sublanguage) can be
embedded in a general-purpose programming
language (host language).
true
_____________ are stand-alone DML commands that can be applied directly.
Query Language
___________ Language is used by the DBA and database designers to specify the conceptual schema of a database.
Data Definition Language (DDL)
T/F: In many DBMSs, the DML is also used to define
internal and external schemas (views).
false, DDL not DML.
In some DBMSs, separate __________ (SDL) and ____________(VDL) are used to define internal and external schemas.
storage definition language, view definition language.
In (Low-level/High-level) DML langauge, Constructs such as looping are needed to retrieve multiple records, along with positioning pointers.
low-level
(Low-level/High-level) DML langauge retrieves data one “record”-oriented (record-at-a-time).
low-level
(Low-level/High-level) DML langauge are “set”-oriented (set-at-a-time) and specify what data to retrieve rather than how to retrieve it.
high-level
(Low-level/High-level) DML langauge are also called declarative languages.
high-level
The SQL relational language is an example of (Low-level/High-level) DML langauge.
high-level.
Name 3 DBMS Interfaces.
- Stand-alone query language interfaces
- Programmer interfaces for embedding DML in
programming languages - User-friendly interfaces (Menu-based, forms-based, graphics-based, mobile-interfaces, natural language [requests in written english])
- Speech : Input query and Output response
- Web Browser with keyword search
Creating user accounts, granting authorizations, Setting system parameters, Changing schemas or access paths are interfaces for the __________.
DBA
__________ are used to store schema descriptions and other information such as design decisions, application program descriptions, user information, usage standards, etc.
Data dictionary / repository
There are two kinds of data dictionaries: _______ data dictionary is accessed by DBMS software and users/DBA, while the ___________ data dictionary is accessed by users/DBA only.
Active, Passive
____________ DBMS Combines everything into single system including DBMS software, hardware, application programs, and user interface processing software.
Centralized
T/F: In a centralized DBMS architecture a user can still connect through a remote terminal. however, all processing is done at centralized site.
true
T/F: In Basic 2-tier Client-Server Architectures, clients can accesss the specialized servers with specialized functions (ex: print server, file server, email server, etc) as needed.
true
T/F: In 2-tier client-server architectures, Clients may be diskless machines or PCs or Workstations with disks with only the client software installed, and are connected to the servers via some form of a
network (LAN: local area network, wireless network, etc.).
true
T/F: In 2-tier client-server architectures, appropriate interfaces are provided through a client
software module to access and utilize the various
server resources.
true
_____________ provides database query and transaction services to the
clients
DBMS Server
_________ DBMS servers are often called SQL servers, query servers, or transaction servers
Relational
T/F: Applications running on clients utilize an Application Program Interface (API) to access server databases via standard interface such as: ODBC or JDBC.
true
T/F: Client and server must install any client
module and server module software for ODBC or
JDBC.
false, must install appropriate,
A client program may connect to several DBMSs,
sometimes called __________.
the data sources.
Three Tier Client-Server Architecture are common for _________ applications.
web
In general, data sources can be ______ or other
____________ that manages data
files, non-DBMS software
In the Three Tier Client-Server Architecture, the intermediate layer called ________ or ________ server.
application, web
The ______________ in the Three Tier Client-Server Architecture, stores the web connectivity software and the business logic part of the application used to access the corresponding data from the database server.
intermediate layer
The ___________ in the Three Tier Client-Server Architecture acts like a conduit for sending partially processed data between the database server and the client.
intermediate layer
T/F: Three-tier Architecture Can Enhance Security.
True, because the database server only accessible via middle tier as in cannot directly access the database server.
Name 3 classifications of DBMSs
- Based on the data model used
- Single-user (typically used with personal computers) vs. multi-user (most DBMSs).
- Centralized (uses a single computer with one
database) vs. distributed (multiple computers, multiple DBs)
Network and Hierarchical are ________ data model based classifications of DBMSs.
legacy
Relational, Object-oriented, Object-relational are ________ data model based classifications of DBMSs.
currently used
Name 3 Variations of Distributed DBMSs
(DDBMSs).
- Homogeneous DDBMS
- Heterogeneous DDBMS
- Federated or Multidatabase Systems
T/F: Distributed Database Systems have now come to be known as client-server based database
systems.
true, because They do not support a totally distributed
environment, but rather a set of database servers
supporting a set of clients
In (homogeneous/Federated or Multidatabase Systems), Participating Databases are loosely coupled with high degree of autonomy.
Federated or Multidatabase Systems
Name 3 Cost considerations for DBMSs.
- Cost Range: from free open-source systems to
configurations costing millions of dollars. - Different licensing options: site license, maximum number of concurrent users (seat license), single user, etc.
- Commercial DBMS offer additional specialized modules.
- Type of access paths within database system.
- General Purpose vs. Special Purpose.
