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Agricultural to Industrial to Information Age

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1 Agricultural to Industrial to Information Age
Data Bits and Bytes e.g Information organized and presented in a form suitable for decision making e.g. (518) Knowledge Ref. Alvin Toffler (1980) Data is raw, unsummarized and unanalyzed facts. We are Data rich and Information poor 1

2 Desirable Attributes of Information
Shareable Transportable Secure Accurate Timely Relevant Readily accessed by more than one person at a time Easily moved to a decision maker Protected from unauthorized use and and destruction Reliable, precise records Current and up to date Appropriate to the decision information: Shareable, Transportable, NOT secure Accurate, Timely & Relevant ? Depends on situation

3 Where do companies get information from?
They buy it Consultants, publications, news services etc. They generate it Computer systems (programs process data stored in databases) Employees (apply experience and intelligence) Who needs it? Higher level managers need less detailed information e.g.. I need your names My chair needs only my class size The president needs only growth trends How is it stored? Tape or disk 2

4 Where do we store Intangible Assets -- Information?
In people’s heads On paper In card-files In computers Computers are like intricate card files with better indexing Information is the content, and the delivery mechanism is technology e.g if a water utility company created the best pipes, taps and dams but when the customer turns it on, brown sludge comes out!!

5 Entities, Attributes, and Relationships
Entity – a person, place, thing, or event Attribute – a property of an entity For the entity “Person,” attributes could include eye color and height Relationship – an association between entities Publishers are related to the books they publish, and a book is related to its publisher Weak or dependent entity (child) is existence-dependent on some other entity type (strong or parent) E.g. next of kin is a weak entity (requires employee) Attributes can be simple or composite (e.g. address)

6 Terminology Fields - attribute
Domain -Description of allowed values for an attribute Records - logically connected set of one or more fields. Files - collection of records A field is some characteristic of the real-world object that is being modeled A domain is the pool of potential values. The concept of a domain is actually too complex for most systems to support

7 History of Data Processing
Manual record-keeping High labor costs and human errors Data file – stores information on a single entity and the attributes of that entity Database – a structure that can store information about multiple types of entities, the attributes of these entities, and the relationships among the entities Manual record keeping works well if you only have to store and retrieve items, but breaks down if you want to cross-reference information. File -based systems are more efficient but take a decentralized approach so a lot of data is duplicated. Each application program defines the physical structure and storage of the data file and records. 4

8 Limitations of File-Based Systems
Separation and Isolation of Data Duplication of Data Data dependence Incompatibility of files Fixed queries / proliferation of application programs / pressure on DP staff 1) Difficult to access data (need to synchronize the processing of two or more files) 2) Duplication wastes time and money with data entry and takes up computer storage space. Also could lead to inconsistencies. 3) For example, to change the size of a field in a file, need to write a new program to replace the original but also need to identify any other program that accesses that file and modify them, even if they do not use that particular field. 4) The structure of a file generated by COBOL is different from that of a file generated by a C program and so cannot process the files jointly 5) All queries and reports have to be written by an application programmer, so no ad hoc queries

9 Database A self-describing collection of integrated records
Properties of a Database: It represents some aspect of the real world It is a logically coherent collection of data with some inherent meaning It is designed, built, and populated with data for a specific purpose It has users and applications A shared corporate resource that has minimum duplication The description of the data is called a system catalog or data dictionary or meta-data. This provides program-data independence If we add a field or create a file, existing applications are unaffected, but if we delete a field from a file that an application program uses, then that program must be modified. 6

10 Spreadsheet or Database?
Data size Data storage format Data structure extent to which relationships among data items are fixed Data sharing Data control degree of data input editing and validating SS can handle about 5000 records, DB can effectively handle up to a million DB can open, use and store files that are pictures, graphs, audio, video, spreadsheets and word documents If relationships are static (use the data in the same way always) SS may be OK, but for dynamic queries, need DB. Number of users who have access to data . If low (e.g if only for acctg dept) use SS, but if acctg, sales and inventory all query the data then it remains undisturbed in a DB. Hi control in DB (e.g. sales data as opposed to forecasting estimates)

11 Static Dynamic Structure Low High Low High Sharing High Low High Low High Low High Low Control Spreadsheet DB Database Either SOLUTION

12 DBMS A software system that :
Enables users to define, create and maintain the database Provides controlled access to this database File processing systems support a limited schema through the creation of directory structures for files They do not support a query language They do not guarantee against data loss if it is not backed up Do not support efficient access to data items whose location in a particular file is not known When they allow concurrent access, they will not prevent two users from modifying the same file at the same time 11

13 DBMS components Machine Data Human Hardware Software Procedures People
Hardware: PC, mainframe or network of computers (e.g. client-server architecture) Software consists of the DBMS software itself along with application programs, the operating system, and network software (if it is used over a network). Data bridges the machine and human components Procedures consist of instructions on how to log on to the DBMS, how to start and stop it, how to make backup copies, handle hardware and software problems etc.

14 Data Life Cycle Data acquisition Data use
data modeling and populating with ultimate goal of storing data Data use Combines data that has been previously stored and interprets output in a decision making context (Data Warehousing) In Access, Tables deal with the first stage of the life cycle (data acquisition) and Queries, Forms and Reports deal with the second stage (data use) 17

15 Data acquisition Logical database design Physical database design
E/R diagrams, normalization, database models Physical database design Integrity constraints, indexes, denormalization Populating the database data entry, import, download Update records data dictionary, metadata Data modeling and design are the responsibility of the IT group whereas populating the database is the responsibility of the functional manager(s) that use the data 18

16 Data Use Define view Retrieve data Manipulate data Present results
Query design, DDL (SQL or QBE) Retrieve data Query performance and optimization, concurrency controls Manipulate data Sort, aggregate, classify, analyze Present results Reports, forms Query design and processing is the province of the IT professionals, whereas manipulation and presentation is the purview of the end-user In Access, Queries deal with the first three and reports and forms deal with the last Forms are primarily used for data entry and reports for printouts 20

17 Access Database Objects
Tables Stores data as records Queries Answers questions about the database Forms Presents data using a customized layout Reports Formats the data (primarily for printouts) Macros Used to automate repetitive tasks Modules Pages Tables contain the permanent data Query datasheets are temporary Modules require programming in Basic. Note: Access automatically saves the active database periodically and when you close. So do not remove the diskette from the drive when the database is open. The SAVE button saves the design of the table, query, form or report. Although for Word you can undo last 100 changes, for Access you can only undo the last one. Access saves changes in the current record as soon as you move to the next or when you close the table.

18 Users Administrators Data Administrator Database Administrator
Database designers Conceptual and logical design (WHAT?) Physical design (HOW?) Application programmers End users naïve (e.g checkout assistant) sophisticated DA manages data and consults with senior managers to ensure that the database supports corporate objectives. The DBA is more technically oriented and is in charge of security and integrity control and ensures satisfactory performance for the application and the users. The importance of the corporate resources is reflected in the allocation of teams of staff to each role (in some organizations there is no distinction between the DA and the DBA) The logical database designer is concerned with the data, the relations between the data and the constraints on the data (must know business rules) 9

19 Everyday Database Systems
Supermarket Credit card Travel Agent Insurance Library University 1) Purchase goods and the barcode reader finds the price of each item from a products database and reduces the number of items on stock. 2) When you use your credit card to purchase goods, a card reader linked to a computer system checks the database to see if the price of goods you wish to buy along with the sum of purchases you have already made this month is within your credit limit. The program also checks that the card is not on the list of lost or stolen cards before authorizing the purchase. When your purchase is confirmed,the details of the purchase are added to the database.

20 Applications of DBMS Airline reservations systems Banking systems
Reservations (customer name, assigned seat) Flights (airports, arrival and departures) Tickets (prices, requirements, availability) Banking systems Customers (names, addresses, accounts, loans) Corporate records Accounts (payable, receivable) Employees (names, addresses, salary, benefits) Airline: Queries: Which seats available and at what prices Modifications: Book a flight, assign a seat, indicate a meal preference Protect against data loss if system fails, Protect against two agents assigning the same seat Banking: Queries: Account balance Modifications: Deposit to account If money has been ejected from ATM machine the bank must record the debit even if the power fails immediately Corporate: Queries: Printing of weekly paychecks Modifications: Employees fired or hired 16

21 Creating a Table in Access
Datasheet view To add, delete or edit records Design View To define table the initially and specify its fields In Word or Excel you can have several documents open at a time. But Access only allows you to open one database at a time. Table names must start with a letter and cannot contain spaces. Field names can contain (not at the start) spaces. Given the choice between one wide field and several narrow ones, the latter is more flexible. (It is easier to concatenate fields than to separate one large field into several sub-fields.) Leave extra room for growth in numeric data items. Do not store calculated data on a record (use dates rather than numbers to represent time duration). .

22 Custom Tables Validation rules Input masks Default values
Lookup fields Format To set a validation rule linking two fields in a table use table properties Input masks ease data entry by providing formatting Lookup wizard can be used to look up values from a field in another table Use >(<) in Format to convert all letters to upper (lower)case Can state criteria for advanced filters Tools->Analyze->Documenter builds a data dictionary for each object in the database

23 Advantages of Database Processing
Getting more information from the same amount of data When all the data for various systems are stored in a single database, the information becomes available, as well as the process of retrieving the information can be quick and easy Combine budget and resources to create important applications for the whole organization. Information is quickly and easily accessible, since it is integrated

24 Advantages of Database Processing
Sharing of data Several users can have access to the same piece of data (Concurrency control allows shared access) Balancing conflicting requirements A person or group, often called Database Administration/Administrator (DBA) can structure the database in such a way that it benefits the entire organization, not just a single group Can write new applications for same data with DBA balancing users’ conflicting requirements

25 Advantages of Database Processing
Controlling redundancy Not only saves space, but makes the updating process easier Consistency Consistency is a direct result of redundancy, so by reducing redundancy, there is much less potential for this sort of inconsistency with the database approach Reducing redundancy improves consistency e.g. in 1805, Austria, Britain, Russia &Sweden were at war with Napoleon. The Austrian and Russian commanders collaborated on a combined attack of the French Army. They agreed to meet on Oct 20th but the Austrians were using the Gregorian calendar whereas the Russians were still using the Julian calendar which was 10 days behind and so the Austrians got wiped out. (However, Napoleon was defeated at the Battle of Trafalgar by Nelson on Oct 21st and so did not invade Britain.) A Mars probe was lost in Sep 1999 due to a mix-up by its flight controllers between imperial and metric units

26 Advantages of Database Processing
Integrity An integrity constraint is a rule that must be followed by data in the database Example: Not allowing a person’s age to be lower than zero Security The prevention of access to the database by unauthorized users Recovery control restores the data to previous consistent state after hardware/software failure According to European legislation, it is a criminal offense if data is not accurate or up-to-date

27 Advantages of Database Processing
Increasing productivity A good DBMS comes with many features that allow users to gain access to data without having to do any programming at all Data independence A property that allows the structure of a database to be changed without the programs that access the database having to change Information is quickly and easily accessible, since it is integrated Reduced program maintenance for programmers due to data independence, improved data accessibility for end-users

28 Disadvantages of Database Processing
DBMS size DBMSs are large programs that occupy a large amount of disk space as well as internal memory DBMS complexity The complexity and breadth of the functions provided by a DBMS make it a complex product to use Mainframe multi-user projects are complex, with recurrent annual maintenance costs Also costs of converting legacy systems (hardware, training etc.) A file-based system is written for a particular application, so performs well, but DBMS is more general, so not as fast.

29 Disadvantages of Database Processing
Greater impact of a failure A failure on the part of any one user that damages the database in some way may affect all the other users on the system More difficult recovery If the database is being updated by a large number of users, all updates must be redone since the time of its restoration Greater vulnerability to multiple users as well as poor design. Failure on the part of any user that damages the database will affect all users sharing that database Multiple users mean that all updates will have to be restored

30 When can an organization justify a database?
Application needs are constantly changing Rapid access is required for ad hoc queries Need to reduce long lead times and high development costs for new systems Data elements are shared by users Need to communicate and relate data across functional and departmental boundaries Need to improve quality of data resources and control access to them Uncertainty as to important data elements and expected volume Substantial dedicated programming assistance is not available Need to improve quality and consistency of data resources 14

31 History of DBMS IBM developed the Generalized Update Access Method (GUAM) in 1964 for North American Rockwell, the prime contractor for the APOLLO project GUAM was made available for the general public under the name Data Language/I (DL/I) in 1966

32 History of DBMS DL/I became the data management component for the Information Management System (IMS), which was the dominant DBMS for many years In the mid-1960s, General Electric developed Integrated Data Store (I-D-S) Enterprises nowadays maintain two distinct databases, one containing operational or production (day to day) data another containing decision support data (summary data that is extracted periodically from the operational database)

33 History of DBMS First generation Second generation Third generation
Hierarchical and network models Second generation Relational models Third generation Object oriented models

34 Data Models Record Based Object Based Hierarchical (60’s)
Network (70’s) Relational (80’s) Object Based Entity-Relationship (70’s) Semantic data models (80’s) Object-oriented (90’s) Relational systems specify what data is to be recovered Network and hierarchical systems specify how the data is to be recovered Even the most complicated hierarchical and network models can be represented using a relational model (2-dimensional tables) Forms the basis for future object oriented databases

35 Record-Based Data Models
Hierarchical Parent-child relationships with only one parent (N:1 relationships are not supported) Network Extends hierarchical model by allowing multiple parents Associations are created via pointers Relational Hierarchical models evolved from tape systems Suited for sequential processing Generally not implemented on PCs DML is more difficult than SQL or QBE Relational DBMS is the dominant data processing software in use today 23

36 Hierarchical Model Perceived by the user as a collection of hierarchies, or trees More restrictive structure than a network model GUAM, DL/I, and IMS are examples of DBMSs that conform to the hierarchical model Represents data as composed of a hierarchy of data records Tree structures (parent-child relationships, with only one parent record type allowed for any record type).

37 Network Model Perceived by the user as a collection of record types and relationships between these record types I-D-S is an example of a DBMS that conforms to the network data model Represents data as records and relationships are represented by sets (records appear as nodes and sets as edges in the graph)

38 Assignment 1 MS Access 2000 Pages AC 2.34 –2.36 #1-16
Database should have at least 4 entities

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