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IS605/606: Information Systems Instructor: Dr. Boris Jukic. Relational Database Systems in Enterprise Information Systems. File systems. File systems rely on coded file management programs to access, insert and modify their content As such, file systems are plagued by two main problems
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IS605/606: Information SystemsInstructor: Dr. Boris Jukic Relational Database Systems in Enterprise Information Systems
File systems • File systems rely on coded file management programs to access, insert and modify their content • As such, file systems are plagued by two main problems • Structural dependence refers to the fact that if a file structure is changed (such as deletion or addition of a field), the related file management programs have to be modified accordingly • Data dependence refers to the fact that the changes in data characteristics, such as changing a field from integer to decimal (or even just changing the length of the field), will cause the related file management programs to be changed • Finally, there is a problem of data redundancy
Data Redundancy • When the same data is stored in more than one location (in multiple files or multiple fields within one file) It may lead to: • Data integrity (inconsistency) problems • may be caused by either data entry errors or failure to update all multiple copies of the same data • Data anomalies: modification, insertion and deletion
Data Redundancy in File Systems and Resulting Anomalies • Modification anomaly: if PlainSounder model description changes • Insertion Anomaly: if a new customer (Toyota for example) is added to the list of those who buy BetterBox product
Database Systems • Database Systems achieve data independence and structural independence • If data type of as filed is changed or a field is eliminated or a new one added, the existing management programs (queries) do NOT have to be modified • If properly designed, databases have a low level of redundancy, eliminating most of the insertion, deletion and modification anomalies • Logically related data instead of physically separated and unrelated files
Four (Logical) Data Models • Hierarchical Model (Legacy) • Standard tree-like structure • Network Model (Legacy) • More than one parent allowed • Relational Model • First truly data and structurally independent model • No predetermined navigational maps as in two older models • The Database technology of choice • Object Model • Tables become objects
RELATIONAL DATABASE ADVANTAGES • Database advantages from a business perspective include • Increased flexibility • Increased scalability and performance • Reduced information redundancy • Increased information integrity (quality) • Increased information security
Relational Database Management System • In RMDBS, all data appears to be stored in a collection of tables (or relations), which are independent of one another, but can be linked through common entries in one of the tables' columns or fields (controlled redundancy) • Relational Schema: The graph depicting relationship types between tables
Reduced Data Redundancy Products Customers
Tables in RDBMS • Tables: Logical constructs containing individual entity sets. • Tables are always two-dimensional: rows and columns • each row represents a single entity (or entity instance) from the entity set • each (uniquely named) column represents one attribute • each row-column intersection results in a single data value • Each table must have a primary key : An attribute uniquely identifying each row (entity), satisfying the entity integrity conditions. Null value (no entry) is not permitted for a primary key. • The order of rows and columns within the table is irrelevant • Foreign Key is an attribute in one table whose values must either match the value of a primary key in another table or be set to null (no value). These conditions are known as referential integrity constraint.
Relationships within the relational database: • One-to-one relationships: • One-to many relationships: • Examples: • professor - class • department - employee • Many to-many relationships • Examples: parts – product, student – class, … • it is recommended to break it into a set (usually two) of one-to-may relationships through a so called composite (bridge) entity
Enterprise data planning • A large component of the business informational needs can be captured by the mapping of all entities the organizations need to keep track of and the relationships among them • E-R (Entity-Relationship) modeling is a standard technique that provides a simplified picture of the relationship among entities.
Keys and Relationships: transaction processing system example
RELATIONAL DATABASE ADVANTAGES • Database advantages from a business perspective include • Increased flexibility • Increased scalability and performance • Reduced information redundancy • Increased information integrity (quality) • Increased information security
Increased Flexibility • A well-designed database should: • Handle changes quickly and easily • Provide users with different views • A database has only one physical view • Physical view – deals with the physical storage of information on a storage device such as a hard disk • A database can have multiple logical views • Logical view – focuses on how users logically access information to meet particular business needs
Increased Scalability and Performance • A database must scale to meet increased demand, while maintaining acceptable performance levels • Scalability – refers to how well a system can adapt to increased demands • Performance – measures how quickly a system performs a certain process or transaction
Reduced Information Redundancy • Databases reduce information redundancy • Redundancy – the duplication of information or storing the same information in multiple places • Inconsistency is one of the primary problems with redundant information
Increase Information Integrity (Quality) • Information integrity – a measure of the quality of information • Integrity constraints – rules that help ensure the quality of information • Operational integrity constraints – rules that enforce basic and fundamental information-based constraints • Business-critical integrity constraints – rules that enforce business rules vital to an organization’s success and often require more insight and knowledge than operational integrity constraints
Increased Information Security • Information is an organizational asset and must be protected • Databases offer several security features including: • Passwords – provide authentication of the user • Access levels – determine who has access to the different types of information • Access controls – Determine types of user access, such as read-only access
DATABASE MANAGEMENT SYSTEMS • Database management systems (DBMS) – software through which users and application programs interact with a database
INTEGRATING INFORMATION AMONG MULTIPLE DATABASES • Organizations typically maintain multiple systems, each with its own database • Integration – allows separate systems to communicate directly with each other
INTEGRATING INFORMATION AMONG MULTIPLE DATABASES • Forward integration – takes information entered into a given system and sends it automatically to all downstream systems and processes
INTEGRATING INFORMATION AMONG MULTIPLE DATABASES • Backward integration – takes information entered into a given system and sends it automatically to all upstream systems and processes
INTEGRATING INFORMATION AMONG MULTIPLE DATABASES • Building a central repository specifically for integrated information