Security, Privacy and Storage: Appunti di Sistemi

Chapter 5. Storing and Organizing Information

DATABASE RELATIONAL DATABASE,

A is an organized collection of data and the most used by organizations are the since

DATABASE MANAGEMENT SYSTEMS (DBMS)

they can store different types of “information”. Databases are managed by

that create, maintain and use databases. Applications handle the processing of data so usually they require data from the

DBMS, which provides them, and after the elaboration data are sent back from the application to the DBMS, which

updates the actual databases with the updated information.

Databases can’t be substituted by spreadsheets because the latter cause problems as data duplication, inconsistent data,

DATABASES

difficult data retrieval and difficult data relations. The main difference between the two is that are good at

SPREADSHEETS

storing and organizing information while are good for analyzing and displaying information visually.

Anyway it is easy to export data from a database into a spreadsheet so it is possible to use both.

Relational databases stores data in the form of connected tables, which are made up of rows (RECORDS, set of field that

TABLE

all pertain to the same thing) and columns (FIELDS, characteristics of the thing). Each stores data about a separate

thing and this structure permits flexibility when you have to retrieve data minimizing redundancy (unnecessary repetition

of facts). Anyway storing each piece of information only once, we ensure consistent data. To identify the data an identifier

PRIMARY KEY

has to be used and it is called (with eventual composite primary keys) that can also be created ex novo.

FOREIGN KEYS

Because the tables are related each other is important to use also to combine them.

The fact that in a relational database each row/column intersection can store at most one item of data permits the system

INCONSISTENCY ONE-TO-MANY,

to eliminate (anomalies or redundant information). The tables can relate each other with

MANY-TO-MANY ONE-TO-ONE

(that requires a creation of a new table that links the two related tables) and relationship.

ENTITY-RELATIONSHIP DIAGRAMS (ERD)

A database can be shown visually thanks to an that shows the data elements and

relationship among them. It is made up of rectangles (tables) with primary keys, foreign keys and fields written inside.

Arrows show the relationships between the tables. Online databases are used by organizations, and not, to reach important information.

Chapter 6. Analyzing Information for Business Decision-Making

Decision-making skills become increasingly important because the higher the levels, the more complex they are and they

have greater impacts. Making good decision requires good information otherwise the impacts are devastating. The

information can have impacts over the constraints of potential alternatives, the alternatives themselves, the forecast of

potential outcomes and the means of comparing alternatives. The decisions range from STRUCTURED (made under

established situations), SEMI-STRUCTURED and UNSTRUCTURED (under emergent situations). The decision making process

has the following steps: identify the problem; define the requirements and goals; identify alternatives; define the criteria;

select the appropriate decision tools; evaluate the alternatives and check the solution).