Explain common XML terminology such as elements, attributes, tags, and entities with examples.
XML (eXtensible Markup Language) is a markup language used to define document structures with a focus on data representation. Here are some common XML terminology definitions with examples:
### 1. Elements
Elements are the fundamental building blocks of XML. An element consists of a start tag, content, and an end tag. Elements can also be nested within other elements.
**Example:**
```xml
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
```
In this example, `<note>` is a parent element that contains four child elements: `<to>`, `<from>`, `<heading>`, and `<body>`.
### 2. Attributes
Attributes provide additional information about elements. They are defined within the start tag of an element and come in name-value pairs.
**Example:**
```xml
<note date="2023-10-01" priority="high">
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
```
In this example, the element `<note>` has two attributes: `date` and `priority`. Each attribute has a corresponding value.
### 3. Tags
Tags are used to define elements. A tag marks the beginning and end of an element. There are two types of tags: start tags and end tags.
**Example:**
```xml
<from>Jani</from>
```
- **Start Tag:** `<from>`
- **End Tag:** `</from>`
Relying on the previous example of the `<note>` element, the full XML structure shows both start and end tags for each element.
### 4. Entities
Entities are a way to represent special characters in XML. They can also be predefined or user-defined. Common predefined entities include `<` for `<`, `>` for `>`, `&` for `&`, and `"` for `"`.
**Example:**
```xml
<note>
<to>Tove <3</to>
<from>Jani</from>
<body>Don't forget me this weekend!</body>
</note>
```
In this example, the text "Tove <3" within the `<to>` element will be displayed as "Tove <3" when rendered, with `<` represented by the entity `<`.
### Summary
- **Elements** are the building blocks of an XML document, comprising a start tag, content, and an end tag (optional in the case of self-closing tags).
- **Attributes** provide additional information about elements and are included in the start tag.
- **Tags** are the markers for the beginning and end of elements.
- **Entities** allow the use of special characters that have specific meanings in XML or that cannot be used directly in text.
By combining these elements, XML allows for the structured and meaningful representation of data.