Ecology lab
Database Management Approaches
Distributed Databases
• Computers, Servers and Databases at various sites
• Connected with communications network or network (internet)
o Computers in a network communicate through messages
• Set up concerns
o Location Transparency
▪ users do not need to be aware of location of data in a distributed database
▪ Remote site: site other than one where user is
▪ Local site: site where user is
o Replication Transparency
▪ making sure data is consistent across vast distances
▪ users unaware of steps taken by DDBMS to update various copies of data
▪ Data replication creates update problems that can lead to data inconsistencies
o Fragmentation Transparency
▪ DDBMS can divide and manage a logical object among various locations under its control
▪ Data placed at the location where it is most often accessed
▪ users unaware of fragmentation
o Communication time
▪ = access delay + (data volume / transmission rate)
▪ Access delay required for every message
Distributions Set ups
• Homogeneous DDBMS
o same local DBMS at each site
• Heterogeneous DDBMS
o at least two sites at which local DBMSs are different
Non-distributed Database System
• One DB, many users connect to it
|Non-distributed System |
|[pic] |
List Advantages/Disadvantages, and identify various issues
|Advantages |Disadvantages |
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|Location Issues (transparency): |
|Replication Issues: |
|Fragmentation: |
|Communication Time: |
Homogeneous DDBMS
• “same” database placed in two (or more) areas to break up traffic
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|[pic] |
List Advantages/Disadvantages, and identify various issues
|Advantages |Disadvantages |
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|Location Issues (transparency): |
|Replication Issues: |
|Fragmentation: |
|Communication Time: |
Heterogeneous DDBMS
• at least two sites at which local DBMSs are different
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|[pic] |
List Advantages/Disadvantages, and identify various issues
|Advantages |Disadvantages |
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|Location Issues (transparency): |
|Replication Issues: |
|Fragmentation: |
|Communication Time: |
Advantages of Distributed Databases
• Local control of data
• Increased database capability
• System availability
• Improved performance
Disadvantages of Distributed Databases
• Update of replicated data
o Primary copy
• More complex query processing
• More complex treatment of concurrent update
o Local deadlock: occurs at a single site in a distributed database
o Global deadlock: involves more than one site
• More complex recovery measures
o Two-phase commit: one site acts as coordinator
• More difficult management of data dictionary
• More complex database design
• More complicated security and backup requirements
Rules for Distributed Databases
• Local autonomy
• No reliance on a central site
• Continuous operation
• Location transparency
• Fragmentation transparency
• Replication transparency
• Distributed query processing
• Distributed transaction management
• Hardware independence
• Operating system independence
• Network independence
• DBMS independence
What do each mean?? (Keep it simple)
Client/Server Systems
• Basic terms
o Server
▪ computer providing data to clients
▪ also called Back-end processor or back-end machine
o Clients
▪ computers connected to a network and used by users to access data
▪ also called Front-end processor or front-end machine
• File server architecture
o stores user files on the network
o NOT a great option if file(s) are routinely used
▪ more requests/longer time to process
|File Server Architecture |
|[pic] |
What are some other advantages/disadvantages??
• Two-tier architecture
o called two tiered since server and client perform completely different tasks
o Server performs ONLY database functions
▪ server ONLY delivers data from queries
• smaller than entire files
o Clients perform presentation (shows and manipulates the data) functions
o Fat client
▪ client performs business applications
• calculations
▪ each client would need to be updated is applications change
o Thin client
▪ server performs the business applications
▪ can cause bottlenecks
▪ but all updates are performed in one spot
|Two-tier architecture |
|[pic] |
• Three-tier architecture
o Clients perform presentation functions
o Database server performs database functions
o Application servers perform business functions and interface between clients and database server
|Three-tier architecture |
|[pic] |
Advantages of Client/Server Systems
• Lower network traffic
• Improved processing distribution
• Thinner clients
• Greater processing transparency
• Increased network, hardware, and software transparency
• Improved security
• Decreased costs
• Increased scalability
Web Access to Databases
• been doing this the entire time!!!
|Web Access to Databases |
|[pic] |
What is XML?
• XML stands for EXtensible Markup Language
• XML is a markup language much like HTML
• XML was designed to carry data, not to display data
• XML tags are not predefined. You must define your own tags
• XML is designed to be self-descriptive
• XML was designed to transport and store data.
• XML provides a robust and SIMPLE format for information storage and transmission
o it uses plain-text file formats
• XML is free.
Why use XML?
• XML allows documents which are all the same type to be created and handled consistently and without structural errors, since it uses
• XML information can be manipulated programmatically (Java, C++),
o XML documents can be pieced together from disparate sources, or taken apart and re-used in different ways.
o They can be converted into any other format with no loss of information.
• XML lets you separate form (appearance) from content.
o Your XML file contains your document information (text, data) and identifies its structure: your formatting and other processing needs are identified separately in a stylesheet or processing system. The two are combined at output time to apply the required formatting to the text or data identified by its structure (location, position, rank, order, or whatever).
What does XML Look like??
• open and closed tags denote fields
• setup much like tables/fields
[pic]
Log into your PHPMyAdmin accounts. “Export” one of your tables to your desktop and take a look.
Data Warehouses
• RDBMS
o remote database management system
o Used for analysis of existing data, and for better performance by moving data not commonly used (or used less often)
• Online transaction processing (OLTP) systems
o Users use transactions when interacting with an RDBMS
o smaller, exact rows of data
o NOT USED FOR MASS QUIERES that merge many tables together
|RDBMS System |
|[pic] |
Online analytical processing (OLAP)
• software for access to a data warehouse
• Data cube: a shape for visualizing a data warehouse as a multidimensional database
• Data mining: uncovering new knowledge, patterns, trends, and rules from data in a data warehouse
Rules for OLAP Systems
• Multidimensional conceptual view
• Transparency
• Accessibility
• Consistent reporting performance
• Client/server architecture
• Generic dimensionality
• Dynamic sparse matrix handling
• Multiuser support
• Unrestricted, cross-dimensional operations
• Intuitive data manipulation
• Flexible reporting
• Unlimited dimensions and aggregation levels
Object-Oriented DBMSs
• Complex objects: graphics, drawings, photographs, video, sound, voice mail, spreadsheets, etc.
• RDBMSs store complex objects using special data types
o Binary large objects (BLOBs)
• Object-oriented DBMSs used with applications whose focus is on complex objects
What Is an Object-Oriented DBMS?
• Object: set of related attributes along with associated actions
• Object-oriented database management system (OODBMS): database management system in which data and associated actions are encapsulated into objects
Introducing the Theory of Objects
• PROGRAMMER DEFINED data types
• int, float, double, etc… all hold ONE variable’s value
o ex:
|Lupoli_age | |Lupoli_IQ | |Lupoli_weight |
|300 | |267 | |200 |
int Lupoli_age = 300;
int Lupoli_IQ = 267;
int Lupoli_weight = 200;
• we would have to create a separate variable for each, even though the variables are ALL related!!
• OBJECT
o group related variables into ONE table/object
|Base Object |Instance #1 |Instance #2 |
|PERSONAL INFO |Aisa |Kenton |
| | | |
|age |21 |21 |
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|IQ |151 |5 |
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|weight |-10 |260 |
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o programmer defined variable
o creating your OWN data type/template
o everything inside a object is GLOBAL or PUBLIC
o need to only create one for each person or “instance”
Why use Objects?
basic data types
• good data type to JUST hold data, very basic (used in C)
What is UML?
• Unified
• Modeling
• Language
• Standard way to specify, construct and document systems that use object-oriented methods
o this is NOT a programming language!!
o stuff you develop in UML will likely later be implemented in an OOP (object-oriented program) language
• nine different diagram types you can use to model a system
o Use case
o Class
o Object
o Sequence
o Collaboration
o Statechart
o Activity
o Component
o Deployment
Why UML
• create top-view diagrams of the BUSINESS processes that allow you to focus on functionality
• lets you start with a generic view while you introduce details later
o (storyboarding??)
• good for non-programmer minded developers
“Use Case” Diagrams
• shows how a business model works from the perspective of those who will use it
o employees, customers, suppliers, etc…
o called actors
• DO NOT necessary represent ALL the functions or functionality of a system ONLY THOSE VISIBLE TO THE “ACTORS”
• using this diagram system will enable you to see division in functional and logical parts
• can use for MULTIPLE actors
[pic]
ALL OF THESE ARE ACTIONS!!!
Create one of STUDENTS, INSTRUCTORS and ADMIN
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Mr. Lupoli
Open Locked Classroom
The Use Case is to open a classroom
Security
The communication in this case is calling
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