Wolf under stars

David Wolf

What is a DTD (Document Type Definition) in XML?

Learn what a DTD (Document Type Definition) is in XML.

When is a XML document valid?

To be valid, an XML document must to meet some requirments. You can find a list of these requirments right here: is well-formed and valid according to the…

When is XML document well-formed?

Example of a well-formed XML document <?xml version="1.0"?> <solar-system> <stars> <star>Sun</star> </stars>…

Database Relations: 1:1, 1:N, N:N

Entities in databases can have relationships with other entities. These relationships are called relations. In this article we will learn about the different…

How to bake cookies using HTTP: The «Set-Cookie» and «Cookie» HTTP headers

You can create a cookie by adding a Set-Cookie HTTP header to an HTTP response. The client browser which receives that response uses the provided directive to…

Introduction into the Hypertext Transfer Protocol (HTTP)

The Hypertext Transfer Protocol (HTTP) is how web browser (client side) and web server (server side) communicate with each other. Communication in terms of…

Rough Overview of the Transmission Control Protocol (TCP)

The Transmission Control Protocol (TCP) is used to transfer data across the internet. On top of that, the protocol ensures that the transferred data retrieves…

Let's bake some Cookies: Introduction into Cookies on the Web (HTTP Cookies)

You heard about cookies. At least, you get penetrated with these annoying "we use cookies" banners or even dialogue boxes. You ever asked yourself…

What is an Entity-Relationship Model (ER Model)?

Entity-relationship models are a graphical abstraction of data models. They can be used to describe how different entities are related to each other. In other…

HTTP Clear-Site-Data: How to force cache clearing for all of your website

Everybody knows this situation: You just rolled out that fresh new feature to your website. It is online now. Yeah. You refresh your website in the browser and…