In software development, semantics refers to the meaning or purpose of code or data. It focuses on what a program is supposed to do, as opposed to syntax, which deals with how the code is written.
a = 5
b = 0
print(a / b)2. HTML Semantics:
<header> instead of <div> for a webpage header.3. Semantic Models:
In software development, syntax refers to the formal rules that define how code must be written so that it can be correctly interpreted by a compiler or interpreter. These rules dictate the structure, arrangement, and usage of language elements such as keywords, operators, brackets, variables, and more.
Language-Specific Rules
Every programming language has its own syntax. What is valid in one language may cause errors in another.
Example:
Python relies on indentation, while Java uses curly braces.
Python:
if x > 0:
print("Positive Zahl")Java:
if (x > 0) {
System.out.println("Positive Zahl");
}Syntax Errors
Syntax errors occur when the code does not follow the language's rules. These errors prevent the program from running.
Example (Syntax error in Python):
print "Hello, World!" # Fehlende Klammern3. Syntax vs. Semantics
4. Tools for Syntax Checking
Variable Naming: Variable names cannot contain spaces or special characters.
Variablenbenennung: Variablennamen dürfen keine Leerzeichen oder Sonderzeichen enthalten.
my_variable = 10 # korrekt
my-variable = 10 # Syntaxfehler{ ... }.
An object-oriented database management system (OODBMS) is a type of database system that combines the principles of object-oriented programming (OOP) with the functionality of a database. It allows data to be stored, retrieved, and managed as objects, similar to how they are defined in object-oriented programming languages like Java, Python, or C++.
Object Model:
Classes and Inheritance:
Encapsulation:
Persistence:
Object Identity (OID):
Complex Data Types:
Object-oriented databases are particularly useful for managing complex, hierarchical, or nested data structures commonly found in modern software applications.
Dynamic HTML (DHTML) is a combination of technologies used to create interactive and dynamic web content. It’s not a standalone standard or programming language but rather a collection of techniques and tools that work together. DHTML enables websites to update content dynamically and provide interactivity without reloading the entire page.
HTML (Hypertext Markup Language)
Provides the basic structure of the webpage.
CSS (Cascading Style Sheets)
Controls the appearance and layout of the webpage. CSS can be dynamically altered to create effects like hover states or style changes.
JavaScript
Adds interactivity and dynamic behavior, such as updating content without a page reload.
DOM (Document Object Model)
A programming interface that allows access to and manipulation of the webpage’s structure. JavaScript interacts with the DOM to change content or add new elements.
Here’s a simple example of a button changing text dynamically:
<!DOCTYPE html>
<html>
<head>
<style>
#text {
color: blue;
font-size: 20px;
}
</style>
<script>
function changeText() {
document.getElementById("text").innerHTML = "Text changed!";
document.getElementById("text").style.color = "red";
}
</script>
</head>
<body>
<p id="text">Original text</p>
<button onclick="changeText()">Click me</button>
</body>
</html>Nowadays, DHTML has been largely replaced by modern techniques like AJAX and frameworks (e.g., React, Vue.js). However, it was a crucial step in the evolution of interactive web applications.
Data Definition Language (DDL) is a part of SQL (Structured Query Language) that deals with defining and managing the structure of a database. DDL commands modify the metadata of a database, such as information about tables, schemas, indexes, and other database objects, rather than manipulating the actual data.
1. CREATE
Used to create new database objects like tables, schemas, views, or indexes.
Example:
CREATE TABLE Kunden (
ID INT PRIMARY KEY,
Name VARCHAR(50),
Alter INT
);2. ALTER
Used to modify the structure of existing objects, such as adding or removing columns.
Example:
ALTER TABLE Kunden ADD Email VARCHAR(100);3. DROP
Permanently deletes a database object, such as a table.
Example:
DROP TABLE Kunden;4. TRUNCATE
Removes all data from a table while keeping its structure intact. It is faster than DELETE as it does not generate transaction logs.
Example:
TRUNCATE TABLE Kunden;DDL is essential for designing and managing a database and is typically used during the initial setup or when structural changes are required.
Platform as a Service (PaaS) is a cloud computing model that provides a platform for developers to build, deploy, and manage applications without worrying about the underlying infrastructure. PaaS is offered by cloud providers and includes tools, frameworks, and services to streamline the development process.
In summary, PaaS enables fast, simple, and flexible application development while eliminating the complexity of managing infrastructure.
A Remote Function Call (RFC) is a method that allows a computer program to execute a function on a remote system as if it were called locally. RFC is commonly used in distributed systems to facilitate communication and data exchange between different systems.
The Document Object Model (DOM) is a standardized interface provided by web browsers to represent and programmatically manipulate structured documents, especially HTML and XML documents. It describes the hierarchical structure of a document as a tree, where each node represents an element, attribute, or text.
Tree Structure:
<html> element, with child nodes such as <head>, <body>, <div>, <p>, etc.Object-Oriented Representation:
Interactivity:
<p> element or insert a new <div>.Platform and Language Agnostic:
1. Accessing an Element:
let element = document.getElementById("myElement");2. Changing Content:
element.textContent = "New Text";3. Adding a New Element:
let newNode = document.createElement("div");
document.body.appendChild(newNode);The DOM is defined and maintained by the W3C (World Wide Web Consortium) standards and is constantly updated to support modern web technologies.
A Software Development Kit (SDK) is a collection of tools, libraries, documentation, and examples that developers use to create applications for a specific platform, operating system, or application programming interface (API). An SDK simplifies and standardizes the development process.
SDKs are typically used for:
The Android SDK includes everything developers need to build Android apps, such as emulators and libraries for Android-specific features like GPS or notifications.
In summary, an SDK streamlines development, reduces complexity, and ensures developers work consistently with the target platform.
A Character Large Object (CLOB) is a data type used in database systems to store large amounts of text data. The term stands for "Character Large Object." CLOBs are particularly suitable for storing texts like documents, HTML content, or other extensive strings that exceed the storage capacity of standard text fields.
TEXT types, which function similarly to CLOBs.TEXT or specialized data types.
Leaner Style Sheets - LESS
