Managing Data Resources Chapter Seven. SoftwareInformation Systems for Management2 Hierarchy of Data Bit Byte Field Record File Database Database management

Managing Data Resources

Chapter Seven

Software Information Systems for Management

2

Hierarchy of Data

• Bit• Byte• Field• Record• File• Database• Database management system


3

Traditional Data Environment

• Files for each application/department/function• Duplicated/redundant data/files• Inability to link data/files• Program-data dependence (change one, you

must change the other)


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Problems with Traditional Data Environment

Data redundancy leads to• Lack of data integrity• Program-data dependence• Lack of flexibility (no ad hoc reports/different

views• Poor security (access)• Lack of data sharing & availability


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DBMS Approach

• Database: Collection of one or more files containing data organized to serve multiple applications by minimizing redundant data.

• Database management system controls organization of & access to data and database files by acting as interface between the data & application programs and as an environment for developing and using databases.


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Views/Schemas

• Logical view: How end users perceive the data is organized– Schema: The view of all the data– Subschema: A partial view of the data accessible to

an end user (e.g., “view only” a subset of screens/data)

• Physical view: How the data are actually organized on physical storage media


7

Components of a DBMS #1

• Data definition language (DDL)– Formal language associated with DBMS– Used by both end users & programmers to

manipulate data

• Data manipulation language– Commands to modify/extract data & to develop apps– Structured Query Language (SQL)– Can use various languages in addition to/ instead of

SQL


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Components of a DBMS #2

• Data dictionary

–Defines each data element (# bytes, text/numeric, etc., format, range, access, use, ownership, physical representation)

–Used for communication between developers & users and for standardization of data/databases/ programs

–Some data dictionaries are active; changes automatically change related databases/programs

NOTE: Any properly developed information system should have a data dictionary.


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Database Models (Types) #1

– Hierarchical• Upside-down tree-like structure• Root (top most data element) is the key field• Each child record can have only one parent record (1:M relationships); parents can have many children• Pointers for expressing relationships• Hard to change & limited retrieval capabilities• “Legacy” systems

– Network• Similar to hierarchical but M:M relationships between

records• Complex and hard to change


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Database Models (Types) #2

• Relational– 2-dimensional tables (relations)– Physically appear similar to files (but are not)– Row/record/tuple– Column/field/attribute/data element– Ability to link relations on-the-fly

• Select creates a subset of all records that meet specified criteria

• Join combines tables into a single new table• Project creates a subset of columns in a table, resulting in

new tables/views


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SQL

• Principal data manipulation language for relational DBMS

• Versions that can run on almost any OS & computer (mainframe, PC, etc.)

• Easy to learn & use– Select lists desired columns from desired table(s)– From identifies tables/views from which to select

columns– Where are conditions for selecting specific records &

for joining multiple tables


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SQL Example

SELECT Part:Part_Number, Supplier:Supplier_Number, Supplier:Supplier_Name, Supplier:Supplier_Address

FROM Part, Supplier

WHERE Part:Supplier_Number=Supplier:Supplier_Number AND Part_Number=137 OR Part_Number=152

Note: No line returns in any of the commands


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Object-Oriented Databases (OODBMS)

• Store data & procedures that act on the data as objects that can be automatically retrieved & shared

• Objects can contain multimedia• Object-relational databases: Relational

databases that can store both traditional data & object-oriented data that store graphics & multimedia


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Designing Databases

• Entity-relationship diagram (E-R diagram)– Documents database by showing relationships

among entities in database

• Normalization– Creates small, stable data structures (tables) from

complex groups of data– Example: Student data: Normalization results in

several DB tables of student data: Name/address, Courses taken, Funds/received/distributed, etc.

– See Figures 7-14 & 7-15

E-R Diagram

ORDER

PART

Includes

Delivered by

SUPPLIER

1

M

M

1Figure 7-13, p. 217


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Distributed Databases

• Stored in more than one physical location• Reduce vulnerability• Increase responsiveness• Can run on cheaper computer systems• Weakness: Vulnerability of telecommunications• Sometimes, locals can depart from acceptable DB

practices– Partitioned: Each remote processor has its own necessary data– Duplicated: Duplicated database (reconciled periodically)


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Data Administration

• Information policy: Planning & rules governing DB operations & information use

• Data planning: Enterprise analysis• Maintenance of data dictionaries• Data quality standards• Database Administration

– Technical– Operational– May include personnel, purchasing, etc. for DB

function


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DB Trends

• Multidimensional Data Analysis– Online analytical processing (OLAP)

• Ability to “slice and dice” data interactively• Multiple perspectives• Matrices or cubes


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Data Warehouses & Datamining

• Data warehouse– Consolidates & stores current & historical data

extracted from various operational systems– Meta-data (summaries of transactional data)– Reporting & query tools, including OLAP & data

mining

• Data mart: Subset of data warehouse• Datamining: Analysis of data in data

warehouses to find patterns/rules to aid in decision making


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Databases & the Web

• Hypermedia database– Organize data in network of nodes linked in user-

specified patterns/relationships– Text, graphics, sound, video, programs

• Linking internal DBs to the Web– Middleware is interface between DB & browser– Application server uses middleware to interface

between DB & browser– Common gateway interface (CGI) written in a

language interfaces between DB, app server, & browser


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Ford & Firestone: Tire Disaster

• Late September, 2001: Firestone recalled another 3.5 million Wilderness tires

• How does this crisis represent an information management problem?

• Why did management of these two companies (and government officials) not see the trends in the data?

• What would you suggest should have been done in terms of database management & queries?


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Next Classes:

• October 17: Midterm– Bring a pencil for Scantron sheets– Bring a pen if you prefer to answer short answer

questions in pen rather than pencil– Room 343: 6-8:00 p.m.– Bring your UM ID; it will be checked

• October 22– Chapter 8: Telecommunications & Networks– Case Study: Monitoring Employees on Networks