Lesson 2 Flashcards
organizational environment in which users own their data exclusively
Flat-file approach
most elemental piece of potentially useful data in the database.
Data attribute
state of data elements being represented in all user files.
Data redundancy
efficient information system that captures and stores data only once and makes this single source available to all users who need it.
-To meet the private data needs of users, organizations must incur the costs of both multiple collection and multiple storage procedures.
Data storage
the periodic updating of data stored in the files of an organization.
This adds significantly to the cost of data management
Data updating
the problem associated with the flat-file model because of its failure to update all the user files affected by a change in status; may result in decisions based on outdated information.
Currency of information
the user’s inability to obtain additional information as his or her needs change.
user’s information set is constrained by the data that he or she possesses and controls.
Task-data dependency
The most obvious change from the flat-file model is the pooling of data into a common database that is shared by all the users.
THE DATABASE APPROACH
software system that controls access to the data resource.
programmed to know which data elements each user is authorized to access
database management system (DBMS)
database model that represents data in a hierarchical structure and permits only a single parent record for each child record.
hierarchical model
individuals who employ systems, receive information, and act on the information received.
Users
a data model that is more flexible than traditional navigational models. It allows users to create new and unique paths through the database to solve a wide range of business problems.
relational model
models that possess explicit links or paths among data elements.
Navigational models
physical arrangement of records in the database.
internal view
Elements of the Database Environment
Users
The DBMS
The database administrator
The physical database
programming language used to define the database to the database management system.
Data definition language (DDL)
description of the entire database.
CONCEPTUAL VIEW (SCHEMA)
set of data that a particular user needs to achieve his or her assigned tasks.
USER VIEW (SUBSCHEMA
a technique used to locate records and navigate through the database.
DBMS OPERATION: Access method
language used to insert special database commands into application programs written in conventional languages.
Data manipulation language (DML)
sequential file structure accessed via an index.
indexed sequential file
The indexed sequential file is a sequential file structure accessed via an index.
Query Language
the individual responsible for managing the database resource.
database administrator (DBA)
description of every data element in the database.
data dictionary
lowest level of the database containing magnetic spots on magnetic disks.
physical database
sequential file structure accessed via an index.
indexed sequential file
a cross-reference created from multiple indexes.
The inverted list
proposed the principles of the relational model in the late 1960s.
E. F. Codd
blueprint for what ultimately will become the physical database.
data model
detailed analysis of the organization’s information needs.
A top-down approach
a client organization’s database developers may modify the model to suit the company’s specific needs.
bottom-up approach
resource, event, or agent
entity
documentation technique used to represent the relationship among data entities in a system.
entity relationship (ER) diagram
high-level perspective of the overall schema, which presents only the key entities and their relationships; it does not show the data types and keys contained within the entities.
entity-level ER diagram
describes how data in one entity are related to data in another entity.
relation
describe the number of instances or records that pertain to a specific entity.
Occurrence
the equivalents to adjectives in the English language that serve to describe the objects.
Attributes
relationship among record types.
Association
numerical mapping between entity instances.
Cardinality
the formal name for a row in the table.
tuple
set of characteristics that uniquely identify each record in the tables.
Primary key
keys that permit the physical connection of logically related tables to achieve the associations described in the data model.
Foreign keys
negative operational symptoms caused by improperly normalized tables.
Anomalies
low degree of normalization of relational database tables.
The first normal form (INF)
table that is free of both repeating group and partial dependencies.
second normal form (2NF)
normalization that occurs by dividing an unnormalized database into smaller tables until all attributes in the resulting tables are uniquely and wholly dependent on (explained by) the primary key.
third normal form (3NF)
an unintentional updating of data in a table, resulting from data redundancy.
update anomaly
an unintentional insertion of data into a table.
insertion anomaly
multiple values for a particular attribute exist in a specific tuple.
Repeating groups
combining the data needs of all users into a single schema or enterprise-wide view
View integration
unintentional deletion of data from a table.
deletion anomaly
one or more nonkey attributes are dependent on (defined by) only part of the primary key rather than the whole key.
Partial dependencies
comprised of two attributes: INVOICE NUM and PROD NUM.
composite key
is reorganizing the IT function into small information processing units (IPUs) that are distributed to end users and placed under their control.
Distributed data processing (DDP)
table where nonkey attributes are dependent on another nonkey attribute and are independent of the table’s primary key.
Transitive dependencies
database retained in a central location.
Centralized database
a firm’s data files accurately reflect the effects of its transactions.
Data currency
occurs during accounting transactions, account balances pass through a state where the values are incorrectly stated.
Temporary inconsistency
software control (usually a function of the DBMS) that prevents multiple simultaneous accesses to data.
database lockout is software control (usually a function of the DBMS) that prevents
database approach that splits the central database into segments or partitions that are distributed to their primary users.
Partitioned database
is a “wait” state that occurs between sites when data are locked by multiple sites that are waiting for the removal of the locks from the other sites.
deadlock
database approach in which the central database is replicated at each site.
Replicated databases
method in which the root segment (customer file) of the database is organized as an indexed file.
Hierarchical indexed direct access method
system that ensures that transactions processed at each site are accurately reflected in the databases at all other sites.
Concurrency control
