Database Management System Chapter 2 – Flashcards
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data modeling
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the process of creating a specific data model for a determined problem domain
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data model
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a representation, usually graphic, of a complex "real-world" data structure. used in the database design phase of the Database Life Cycle
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entity
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a person, place, thing, concept, or event for which data can be stored
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attribute
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a characteristic of an entity or object. has a name and a data type
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relationship
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an association between entities
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one-to-many (1:M or 1..*) relationship
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associations among two or more entities that are used by data models. one entity instance is associated with many instances of the related entity
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many-to-many (M:N or *..*) relationship
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association among two or more entities in which one occurrence of an entity is associated with many occurrences of a related entity and one occurrence of the related entity is associated with many occurrences of the first entity
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one-to-one (1:1 or 1..1) relationship
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associations among two or more entities that are used by data models. one entity instance is associated with only one instance of the related entity
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constraint
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a restriction placed on data, usually expressed in the form of rules. help to ensure data integrity
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business rule
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a description of a policy, procedure, or principle within an organization
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hierarchical model
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an early database model whose basic concepts and characteristics formed the basis for subsequent database development. based on an upside-down tree structure in which each record is called a segment. the top record is the root segment. each segment has a 1:M relationship to the segment directly below it
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segment
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in the hierarchical data model, the equivalent of a file system's record type
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network model
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an early data model that represented data as a collection of record types in 1:M relationships
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schema
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a logical grouping of database objects, such as tables, indexes, views, and queries, that are related to each other
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subschema
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the portion of the database that interacts with application programs
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data manipulation language (DML)
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the set of commands that allows an end user to manipulate the data in the database, such as SELECT, INSERT, UPDATE, DELETE, COMMIT, and ROLLBACK
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data definition language (DDL)
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the language that allows a database administrator to define the database structure, schema, and subschema
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relational model
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developed by E. F. Codd of IBM in 1970, the relational model is based on mathematical set theory and represents data as independent relations. each relation (table) is conceptually represented as a two-dimensional structure of intersecting rows and columns. the relations are related to each other through the sharing of common entity characteristics (values in columns)
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table (relation)
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a logical construct perceived to be a two-dimensional structure composed of intersecting rows (entities) and columns (attributes) that represents an entity set in the relational model
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tuple
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in the relational model, a table row
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relational database management system (RDBMS)
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a collection of programs that manages a relational database. the software translates a user's logical request (queries) into commands that physically locate and retrieve the requested data
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relational diagram
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a graphical representation of a relational database's entities, the attributes within those entities, and the relationships among the entities
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entity relationship (ER) model (ERM)
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a data model that describes relationships (1:1, 1:M, and M:N) among entities at the conceptual level with the help of ER diagrams. developed by Peter Chen
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entity relationship diagram (ERD)
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a diagram that depicts an entity relationship model's entities, attributes, and relations
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entity instance (entity occurrence)
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a row in a relational table
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entity set
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a collection of like entities
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connectivity
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the type of relationship between entities. classification include 1:1, 1:M, and M:N
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Crow's Foot notation
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a representation of the entity relationship diagram that uses a three-pronged symbol to represent the "many" sides of the relationship
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class diagram notation
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the set of symbols used in the creation of class diagrams
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object-oriented data model (OODM)
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a data model whose basic modeling structure is an object
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object
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an abstract representation of a real-world entity that has a unique identity, embedded properties, and the ability to interact with other objects and itself
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object-oriented database management system (OODBMS)
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data management software used to manage data in an object-oriented database model
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semantic data model
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the first of a series of data models that more closely represented the real world, modeling both data and their relationships in a single structure known as an object. published in 1981, was developed by M. Hammer and D. McLead
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class
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a collection of similar objects with shared structure (attributes) and behavior (methods). encapsulates an object's data representation and a method's implementation. organized in a class hierarchy
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method
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in the object-oriented data model, a named set of instructions to perform an action. represent real-world actions, and are invoked through messages
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class hierarchy
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the organization of classes in a hierarchical tree in which each parent class is a superclass and each child class is a sublcass
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inheritance
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in the object-oriented data model, the ability of an object to inherit the data structure and methods of the classes above it in the class hierarchy
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Unified Modeling Language (UML)
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a language based on object-oriented concepts that provides tools such as diagrams and symbols to graphically model a system
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class diagram
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a diagram used to represent data and their relationship in UML object notation
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extended relational data model (ERDM)
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a model that includes the object-oriented model's best features in an inherently simpler relational database structural environment
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object/relational database management system (O/R DBMS)
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a DBMS based on the extended relational model (ERDM). the ERDM, championed by many relational database researchers, constitues teh relationsl model's response to the OODM. includes many of the object-oriented model's best features within an inherently simpler relational database structure
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Extensible Markup Language (XML)
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a metalanguage used to represent and manipulate data elements. permits the manipulation of a document's data elements. facilitates the exchange of structured documents such as orders and invoices over the Internet
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Big Data
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a movement to find new and better ways to manage large amounts of web-generated data and derive business insight from it, while simultaneously providing high performance and scalability at a reasonable cost
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3 Vs
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three basic characteristics of Big Data databases: volume, velocity, and variety
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Hadoop
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a Java based, open source, high speed, fault-tolerant distributed storage and computational framework. uses low-cost hardware to create clusters of thousands of computer nodes to store and process data
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Hadoop Distributed File System (HDFS)
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a highly distributed, fault-tolerant file storage system designed to manage large amounts of data at high speeds
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name node
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one of the three types of nodes used in the Hadoop Distributed File System (HDFS). stores all the metadata about the file system
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data node
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one of three types of nodes used in the Hadoop Distributed File System (HDFS). stores fixed-size data blocks (that could be replicated to other data nodes)
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client node
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on of three types of nodes used in the Hadoop Distributed File System (HDFS). acts as the interface between the user application and the HDFS
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MapReduce
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an open-source application programming interface (API) that provides fast data analytics services; one of the main Big Data technologies that allows organizations to process massive data stores
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NoSQL
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a new generation of database management systems that is not based on the traditional relational database model
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key-value
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a data model based on a structure composed of two data elements: a key and a value, in which every key has a corresponding value or set of values. also called the associative or attribute-value data model
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sparse data
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a case in which the number of table attributes is very large but the number of actual data instances is low
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eventual consistency
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a model for database consistency in which updates to the database will propagate through the system so that all data copies will be consistent eventually
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American National Standards Institute (ANSI)
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the group that accepted the DBTG recommendations and augmented database standards in 1975 through its SPARC committee
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external model
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the application programmer's view of the data environment. works with a data subset of the global database schema
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external schema
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the specific representation of an external view; the end user's view of the data environment
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conceptual model
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the output of the conceptual design process. provides a global view of an entire database and describes the main data objects, avoiding details
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conceptual schema
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a representation of the conceptual model, usually expressed graphically
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software independence
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a property of any model or application that does not depend on the software used to implement it
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hardware independence
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a condition in which a model does not depend on the hardware used in the model's implementation. therefore, changes in the hardware will have no effect on the database design at the conceptual level
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logical design
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a stage in the design phase that matches the conceptual design to the requirements of the selected DBMS and is therefore software-dependent. used to translate the conceptual design into the internal model for a selected database management system, such as DB2, SQL Server, Oracle, IMS, Informix, access, or Ingress
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internal model
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in database modeling, a level of data abstraction that adapts the conceptual model to a specific DBMS model for implementation . the representation of a database as "seen" by the DBMS. requires a designer to match the conceptual model's characteristics and constraints to those of the selected implementation model
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internal schema
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a representation of an internal model using the database constructs supported by the chosen database
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logical independence
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a condition in which the internal model can be changed without affecting the conceptual model. (the internal model is hardware-independent because it is unaffected by the computer on which the software is installed. therefore, a change in storage devices or operating systems will not affect the internal model)
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physical model
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a model in which physical characteristics such as location, path, and format are described for the data. both hardware- and software-dependent
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physical independence
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a condition in which the physical model can be changed without affecting the internal model
