Lesson 2 Data Modeling And Data Models Flashcards
Data modeling
The process of creating a specific data model for a determined problem domain. This is an iterative, progressive process.
Data model
Simple representation, usually graphical of more complex real world data structures. Main function is to help you understand the complexities of the real world environmentDescription of the data structure that will store the end user dataA set of enforceable rules to guarantee the integrity of the dataA data manipulation methodology to support the real world data transformations
Entity
A person, place, thing or event about which data will be collected and stored. May be physical objects or abstractions such as flight routes.
Attribute
Characteristic of an entity
Relationship
An association among entitiesCan be one to may,Many to many,and One to one
Building blocks of a data model
EntityAttributeRelationship
One-to-many (1:M or 1..*) relationship.
Each record from first table is associated with many records in second table but each record in second table is associated with one record in first table
Many-to-many (M:N or ..) relationship.
Each record from first table is associated with many records in second table and one record in second table is associated with many records in first table
One-to-one (1:1 or 1..1) relationship.
Single record in the first table is related to only one record in the second table and vice versa
Constraint
A restriction placed on the data such as a GPA must be between 0.00 and 4.00
Business rule
Brief, precise, and unambiguous description of a policy, procedure, or principle within a specific organization.Derived from a detailed description of an organizations operationsMust be rendered in writing and updated to reflect any changes in the organization's operational environmentUsed to define entities, attributes, and relationships, and constraints.
Business rules are essential for a database because
It helps to standardize the company's view of dataIt can be a communication tool between users and designersIt allows the designer to understand the nature, role, and scope of the data.It allows the designer to understand business processesIt allows the designer to develop appropriate relationship participation rules and constraints and to create an accurate data model
Noun in a business rule
Translate into an entity in the model
Verb in a business rule that associates the nouns
Translates into a relationship among entities
Properly identify relationship type
How many instances of B are related to one instance of A?How many instances of A are related to one instance of B?In how many classes can one student enroll? Answer: many classes.How many students can enroll in one class? Answer: many students.Therefore, the relationship between student and class is many-to-many (M:N)
Entity Names
According to the data-modeling checklist, _____ should be nouns that are familiar to business, should be short and meaningful, and should document abbreviations, synonyms, and aliases for each entity.
Attribute names
Descriptive of the data represented by that attributePrefix the name of an attribute with the name or abbreviation of the entity in which it occursFor example, in the CUSTOMER entity, the customer's credit limit may be called CUS_CREDIT_LIMIT.
Hierarchical model
Basic logic structure represented by an upside down treeContains levels or segmentsThe top record is the root segment. Each segment has a 1:M relationship to the segment directly below it.Each parent can have many children, but each child has only one parent
Segment
The equivalent of a file systems record type within a Hierarchical model
Network Model
An early data model that represented data as a collection of record types in 1:M relationships.More effective than the hierarchical modelAllows a record to have more than one parent
Schema
Conceptual organization of the entire database as viewed by the database administrator
Subschema
Defines the portion of the database seen by the application programs that actually produce the desired information from the data within the database
Data Manipulation Language (DML)
Defines the environment in which data can be managed and is used to work with the data in the database
Data Definition Language (DDL)
Enables the database administrator to define the schema components
Relational model
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).
Table relation
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.
Tuple
In the relational model, a table row
Relational database management system (RDBMS)
A collection of programs that manages a relational database. The RDBMS software translates a user's logical requests (queries) into commands that physically locate and retrieve the requested data.Hides complexities of the relational model from the userTables are related to each other through the sharing of a common attribute (A value in a column)Easily associate the data between independent tables
Relational diagram
A graphical representation of a relational database's entities, the attributes within those entities, and the relationships among the entities.
End user interface
The interface that allows the end user to interact with the data(by automatically generating SQL code)
Collection of tables stored in the database
In a relational database, all data is perceived to be stored in tables. Each table is independents. Rows in different tables are related by common values in common attributes
SQL engine
Executes all queries
Entity relationship model (ER)
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. The model was developed by Peter Chen.
database terms
Entity: It is a "thing" or "object" in our environment that we want to keep track of.Record: It is a collection of related data items.Attribute: It is a property of, a characteristic of, or a fact that we know about an entity.Field: The fact is represented as a column.Entity set: It is a collection of entities of the same type.File: It is an entire structure.
object-oriented data model (OODM)
Both data and its relationships are contained in a single structure known as an object
Object
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
Object-oriented database management system (OODBMS)
Data management software used to manage data in an object-oriented database model.Attributes describe the properties of an object. For example, a PERSON object includes the attributes Name, Social Security Number, and Date of Birth.Objects that share similar characteristics are grouped in classes
semantic data model
The first of a series of data models that more closely represented the real world.
Class
A collection of similar objects with shared structure(attributes) and behavior(methods)
Structure
Attributes
Behavior
Methods
Method
Represents a real world action such as finding a selected PERSON's name, changing a PERSON's name, etc...
Class diagram
A diagram used to represent data and their relationships in UML object notation.
Unified Modeling Language
A language based on objected-oriented concepts that provides tools such as diagrams and symbols to graphically model a system
Inheritance
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
Class hierarchy
The organization of classes in a hierarchical tree in which each parent class is a superclass and each child class is a subclass
NoSQL
Database management systems that handle non-relational data like documents, increasingly used for maintaining and querying the large amounts of data from the Internet. Queries can be made using "Not only Structured Query Language."
extended relational data model (ERDM)
A model that includes the object-oriented model's best features in an inherently simpler relational database structural environment
3 Vs of Big Data
volume, velocity, variety
Hadoop
A Java based, open source, high speed, fault-tolerant distributed storage and computational framework. Hadoop uses low-cost hardware to create clusters of thousands of computer nodes to store and process data.
Hadoop Distributed File System (HDFS)
A highly distributed, fault-tolerant file storage system designed to manage large amounts of data at high speeds. Write once, read many model. Once data is written it cannot be modified
MapReduce
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.
key value
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. The key-value data model is also called the associative or attribute-value data model.