Notes, summaries, assignments, exams, and problems for Computers

Test Strategy

• Test Planning
• Design test cases
• Test Run
• Collection and evaluation

The software is tested to discover errors made inadvertently when carrying out their design and construction.

The tests are a set of activities you can plan ahead and carry out systematically. For this reason, you must define the process of software engineering template for software testing.

A software testing strategy should include: evidence of low-level, high level evidence.

Verification: a set of activities to ensure that software correctly implements a specific function.

Validation: different set of activities to ensure that software built is consistent with customer requirements.

Only once the software architecture comes into play is completed Independent Test Group.

Starting a Session and Destroying Variables (inicio.php)

session_start();
unset($_SESSION["host"]);

Creating a Session and Attempting a Connection (marco.php)

session_start();
$conn = @mysql_connect($host, $user, $password) or die("Incorrect user or password");
@mysql_select_db($db, $conn) or die("Cannot open the DB");

Assigning Connection Parameters to Session Variables

$_SESSION["host"] = $host;
$_SESSION['User'] = $user;

Starting a Session, Connecting to the Database, and Sending an Insertion Query (altas.php)

<?
 session_start();
 $conn = mysql_connect($host, $user, $password) or die("Incorrect user or password");
 mysql_select_db($db, $conn) or die("Not selected");
 $query = "insert into departments values ($dep, '$nom', '$crazy')";
 $result

Features of Free Software

Free software provides the following freedoms:

• The freedom to run the program for any purpose.
• The freedom to study how the program works and adapt it to your needs.
• The freedom to redistribute copies so you can help others.
• The freedom to improve the program and release improvements to the public, so that the whole community benefits.

Sharing Resources in Windows

To share network resources in Windows, you need to ensure that file and printer sharing is enabled in the local area network configuration. To do this, go to "Network Connections", right-click on "Local Area Connection", and select "Properties".

Types of Users

• Administrator or Root: Responsible for configuration and maintenance.
• User: Uses the system and accesses resources

Processor Front

The processor front involves three components: source, destination, and message. The source (e.g., a terminal or computer) sends a message. The destination (e.g., another terminal or computer) receives the message. The front-end processor acts as the connection between the source and destination, managing the message transfer. It frees the host processor from communication tasks, handling message routing, transmission monitoring, code translation, and encryption. All data transmitted to or from the host processor are managed through this specialized front-end processor, allowing the host processor to operate more efficiently and focus on application processing.

Types of Communications

A network enables computer connections to share... Continue reading "Computer Network Communications" »

Software Development Models

Attributes of Effective Requirements (AtrERS): Correct, unambiguous, complete, verifiable, consistent, modifiable, concise, organized, searchable, understandable by the client, regardless of design.

Scaling Factors: Correctness, reliability, efficiency, integrity, ease of use and maintenance, flexibility, ease of testing, portability, reusability, ease of interoperation.

Life History: Succession of stages through which a software product passes during its existence. Attempts to determine the order of the steps involved and the criteria associated with the transition between these stages.

Software Engineering: Application of scientific knowledge to the design and construction of computer programs and associated documentation... Continue reading "Software Development Models: Waterfall, Prototype, and More" »

Advanced Features

Advanced features facilitate consultation similar to a spreadsheet because they work based on rows and columns.

• COUNT(): Count the number of rows in the column set
• MIN(): Find the minimum value of the column set
• MAX(): Find the maximum value of the column set
• AVG(): Gets the average values in the column set
• SUM(): Gets the total value implied by the values obtained in the column provided

Modifying the Database

SQL DDL has modules for the definition of data that allows us to create or modify table structure.

The instructions for these operations are:

• CREATE TABLE: Allows you to create an empty data table.
• INSERT: Allows you to store records in a table created.
• UPDATE: You can modify data records stored in the table.
• DELETE: Deletes a record

System Calls: Core OS Interaction

A system call is the mechanism used by an application program to request a service from the operating system.

How a System Call is Made

When a call is made, it involves placing a set of parameters in a specific memory location and then executing a machine language instruction for the processor.

Common POSIX System Calls

In operating systems, common POSIX system calls include: open, read, write, close, wait, exec, fork, exit, and kill.

Understanding Processes

A process is an abstraction of a running program, also referred to as a task.

Process Model Properties

1. All software executables are organized into several sequential processes.
2. A process includes the running program, the current values of the program counter, registers,

Web Engineering Models

Data Model

Compatible with the entity-relationship model and UML class diagrams.

Hypertext Model

• Composition: Site pages, content units of pages.
• Unit: Atomic content element, used to publish the information specified in data models.
• Navigation: Specified by links.
• Links: Between units of a page, between units of different pages, or between pages.
• Defines both the content and navigation.

Presentation Model

• The appearance of web pages.
• Does not include specific elements for conceptual modeling; notations are used.
• XML.
• The presentation is specified using XSL stylesheets.

Web Engineering UML-Based Methodology (UWE)

• Proposal based on UML and the Unified Process, adapted to the web.
• Specific object-oriented techniques are used.
• Proposes an

Network Topologies

Ring Topology

Connects hosts in a physical ring. The last host connects to the first.

Star Topology

Connects all cables to a central point.

Extended Star Topology

Connects individual stars using hubs or switches, extending network coverage.

Hierarchical Topology

Similar to extended star, but uses a computer to control traffic instead of hubs/switches.

Mesh Topology

Provides maximum protection by connecting each host to others, ensuring service continuity.

Network Communication Methods

Broadcast

Each host sends data to all others on the network. Access is first-come, first-served (e.g., Ethernet).

Transmission Tokens

Controls access via sequential token transmission. Hosts send data when they have the token (e.g., Token Ring, FDDI).

Network

AI Meets AI: Leveraging Query Executions to Improve Index Recommendations

How artificial intelligence (AI) can benefit automated indexing (AI)?: Comparing the execution cost of two plans (different index configurations of same query) is key for index tuning. Instead of using optimizer’s estimates for such comparison, formulating it as a classification task in machine learning results in significantly higher accuracy.

MOTIVATION:

• Being able to fully automate index recommendation and implementation is a significant value-add for improving query execution cost.
• Requirement: creating or dropping indexes should not cause significant query performance regressions - users enforce a no query regression constraint.
• Using the optimizer’s estimates to