SMA

XML and JSON

• Markup Language (like HTML)
• Designed to store and transport data
• Self-descriptive
• hierarchical/tree structure with root element, that contains all the other elements of a document
• The base unit of XML are elements (block of text within a document, pair of tags): 
  • start and end tag (names can be choosen freely)
  • <paragraph> Paragraph text </Paragraph text>
• You can only write text in the lowest tags (title and paragraph in this case)

The Document Type Definition (DTD) define the components allowed in the construction of an XML document

• Defines the legal elements and attributes within the document. You cannot use any other elements except those defined. A kind of "vocabulary" for the files that will use it
• It defines the structure of each element (e.g., what each element can contain, the order, the quantity of elements that can appear, etc.). A kind of "grammar"
• Finally, it provides some mechanisms to simplify document management (e.g., the ability to import parts of other DTDs

An XML Schema describes the structure of an XML document

• The XML Schema language is also referred to as XML Schema Definition (XSD)
• XML Schema is an XML-based (and more powerful) alternative to DTD.

The purpose of an XML Schema is to define the legal building blocks of an XML document:

• The elements and attributes that can appear in a document
• The number of (and order of) child elements
• Data types for elements and attributes
• Default and fixed values for elements and attributes 

DTD wird nicht in XML-Sprache geschrieben, XML Schema (XDS) gingegen schon

HyperText Transfer Protocol (HTTP) is an application layer protocol used as the primary system for transmitting information on the Web. 

• HTTP is a protocol that works with a Client/Server architecture: the client executes a request, and the server returns the response
• In common use, the client is the browser and the server is the remote machine on which the Website resides.
• There are therefore two types of HTTP messages: request messages and response messages.

Web is based on client/server network --> so it is centralized (in regards to infrastructure and content-creation)

The Decentralized Web is like the World Wide Web we have today, filled with amazing, interactive content and information — the only difference is that the underlying architecture is decentralized, so that it becomes much harder for any one entity (whether through malicious censorship or accidental failure) to take down any single Web page, website, or service.

Nowadays we are in an era of the dynamic web (e.g.flight booking page --> dynamically generates resultspage depending on search terms)

Simple scripts (like hover menu or simple presentation things) are on the client side and can be seen in the source of the page

More complex things (light flight blooking) are on the server-side an I can't see it in the source code of the page

• Web 1.0 is a retronym that refers to the first stage of the evolution of the World Wide Web
• In Web 1.0 most users can enjoy the contents but only a small part (the experts) become content generators. Content managed by server's file system instead of DBMS.
• Web Pages connected by hyperlinks (static instead of dynamic)
• Menus created through the use of GIF images, pages structured in frames
• Web characterized by one-way communication 
• Initially through the mailto protocol: a user fills out a form and, by clicking on the form submit button, her/his email client starts and tries to send an email containing the form details 

• First used by Darcy DiNucci in 1999 and popularized several years later by Tim O'Reilly and Dale Dougherty 
• Web 2.0 does not refer to an update of any technical specification, but to changes in the way Web pages are designed and used
• The transition has been gradual and there is no precise date that can identify the transition between Web 1.0 and Web 2.0 
• A Web 2.0 site can allow users to interact and collaborate with each other in virtual communities, generating and exchanging content.
• Web 2.0 gives almost all users the same freedom to contribute (communication is bidirectional)

Compared to Web 2.0, Web 3.0 has the following evolutionary aspects:

• Semantic Web and Artificial intelligence, associated with a more structured data storage ⇒ Possibility of developing search engines that allow querying through natural language and the retrieval of information through AI
• Greater computing capacity and new algorithms aimed at the construction of truly usable 3D environments

• Term coined by Tim Berners-Lee
• Transformation of the Web into an environment where documents (HTML pages, files, images, and so on) are associated with information and data (metadata) that specify their semantic context in a format suitable for querying and interpretation (e.g., through search engines) and, more generally, automatic processing
• Information can be expressed with assertions consisting of triples formed by subject, predicate and value (subject, verb, object)

Resource Description Framework (RDF) ⇒ allows semantic interoperability between applications that share information on the Web.

• Web 3.0 and 4.0 are not clearly defined and differentiated
• Web 4.0 is not used by a lot of people and is still in development
• Augmented Reality (e.g. Smart Glasses)
• Digital alter ego: As we populate the web with our personal contents, we will create a real virtual alter ego, which will allow us to make the two identities interact in real-time: the real one and the digital one
• New interfaces, Meta-verse

• Virtual Data
• Digitized Data
• Digital Data

Concept is related to social presence

 The concept of self-presentation is related to the concept of self-disclosure