cs paper 2

what is the internet, go from internet to web page. and what is a url

internet: globally connected network system

internet-www-website-webpage

URL (Uniform Resource Locator): address you type into a browser to visit a website or search something online

accessing a website

every website is stored on a server, you send a request to that server when accessing

Browser → asks DNS server → gets IP → contacts web server → gets webpage

what is a DNS

DNS (Domain Name Server): translates human readable domain names into machine readable IP addresses, used when accessing a website

• like a phonebook

what is a protocol and the types

protocol: a set of rules that govern how data i transmitted ex.HTTP,TCP/IP

• format, time, sequencing

• important for communication, packet switching

1. HTTP (Hypertext Transfer Protocol)

   • used for transmitting information on the WWW, used used anytime you request a webpage

   • requests response between server and client

2. HTTPS (Hypertext Transfer Protocol Secure)

   • secure version of HTTP

   • data is encrypted using SSL which is established at the IP step

3. TCP/IP

   • Makes sure the messages are broken into smaller packets and reassembled correctly

TCP/IP vs HTTP

• TCP/IP: how the data travels (ex. roads, vehicles)

• HTTP: what the message says (ex. language, what you want)

What are ports

doors that allow programs to send and receive data over a network-reach the right service

• important for running multiple networks on a device

• HTTP sends a request to the web using a port number

static vs dynamic web pages

static: fixed content, same for every visitor, no server side processing (HTML) ex. about us, menu

dynamic: dynamic content, changes for every visitor, server side processing (PHP, java) ex. instagram, amazon, facebook

client-side scripting vs server-side scripting

Client-side scripting: can run in your browser, adds interactive behavior (HTML, CSS)
Server-side scripting: runs on a server, handles user login, databases (PHP, Python).

XML (extensive markup language)

like HTML, but it’s used to structure data so computers can read and share it easily

• both human and machine language

web browser vs search engine

web browser: application used to access and display www content ex. chrome, safari

search engine: a program that enables searching information with keywords, phrases, uses algorithms to search through data

search engine process

1. Crawling: search engine crawler scans the web, following links, collecting content

2. Organizing: Content is organized and stored in an index (page info, title, URL)

3. Ranking: Algorithm retrieves the most relevant pages and ranks them

4. Deliver results: Based on ranking, relevance, authority, freshness, user experience

Metatags: HTML tags that give info about a webpage and help search engines understand content, stored in the head section

Search engine algorithm types

1. Page Rank (google’s alogirthm) “General importance”

   • based on how many pages link to it

   • each page given a score between 0 and 1

   • fewer outlinks means higher value

2. HITS (hyperlink induced algorithm) “hub or authority”

   every page gets 2 scores:

   1. Authority (experts): number and quality of incoming links

      • good authority if many good hubs link to it

   2. Hub (recommenders): number of outgoing links

      • good hub if if it links to many good authorities

types/layers of webs

1. Surface Web 0.5%

   • content accessible by standard engine, and is publicly available

2. Deep Web 99.5%

   • private databases hidden behind logins or firewalls

3. Dark Web 0.01%

   • Intentionally hidden, usually illegal

   • Requires specialized software like TOR

what is SEO and types

SEO-search engine optimization: improving a website so it appears higher on search engine results

1. white hat SEO: ethical ways to optimize results

   • keyword optimization

   • content creation

   • link building

2. black hat SEO: unethical techniques

   • cloaking

   • link farming

   • hidden texts

Computing types

computing: use of computers to perform calculations, process data, run programs

1. Grid computing: a network of connected computers solving complex tasks over a network in different geographical locations

   PROS: can solve complex problems faster, easy collaboration

   CONS: Security risks due to sharing data, complex set up, relies on network connectivity

2. Mobile computing: use of portable devices

   PROS: portability, cost, connectivity

   CONS: limited screen size, battery life, security risks

3. Ubiquitous computing: concept of integrating computer technology into daily lives

   ex. mobile devices, smart homes, brainchips

   PROS: convenience, improvement of quality of life

   CONS: privacy concerns, security risks, technological dependency

4. P2P computing: decentralized network where each computer acts as both a server and a client

   PROS: effective sharing, cost effective, enhanced privacy, fault tolerance

   CONS: lack of control, scalability/lack of resources

5. Cloud computing: use of remote servers, computing over the internet

   PROS: flexibility, scalability, cost effective

   CONS: security concerns, downtime, dependency on 3rd party

Interoperability and standards

• different systems, devices, applications working together

1. Standardization: interoperability relies on standardized protocols, formats, interface

2. standards: guidelines making sure everyone builds systems the same way

   • open standards: publicly available specifications ex. HTML, bluetooth, TCP/IP

   • benefits: interoperability, innovation, longevity

3. Flexibility: Interoperability systems are designed to be flexible, allowing a range of systems

ISO and creative commons license

ISO (international organization for standardization): creates standards internationally

creative commons license: work is publicly available, but authors still have control over how its used, like a copyright

graph theory

• used to represent how websites are connected

directed graph (web graph):

1. core (SCC): central, most densely connected part of the web, small number of highly interconnected pages (ex. reddit, google, facebook)

2. In components: pages that have links to the core, none from the core (ex. a blog linking google)

3. out components: pages the core links out to (ex. news site linked on reddit)

4. Tendrils: connect to the in and out groups but not directly to the core (ex. small blog linking a news site, but no big sites link back to it)

5. Tubes: pages that link the in and out section, like a shortcut (ex. blog linking booking site and is also linked from other blogs)

Diameter: longest shortest path between 2 pages, worst case scenario how many links it takes

Ambient and collective intelligence

ambient: technology built into the environment, use of sensors, networks ex. smart home

collective: a group of individuals pooling their knowledge to solve tasks, decisions ex. wikipedia, google traffic

power law distribution and ontology, folksonomy

power law distribution: small number of pages have a disproportionately number of links

• it’s why the web graph is highly centralized around a few core hubs

• Inequality

ontology: organize and categorize knowledge for computers

• ex. medicine: so computers can organize and understand data

folksonomy: tagging done by regular people

• models natural behavior

• ex. social media, #