HTTP

• What is the first part of a CSS rule?
• How are the selectors and DOM related?
• How are the DOM and Javascript related?
• What does href in the anchor tag mean?
• How are animations accomplished with Javascript?

• URL used day-to-day
• URL technically a type of URI
• URL provides both an identifier and a way to locate it (eg. protocol and

server)

• URN almost never used in the web, though seeing some pickup on mobile (eg.

tel:)

• "Resource" something we'll cover more in depth, but for the common case it is a file
• Technically any concept you can "name" or "identify" is a resource

• http://www.yelp.com/biz/jupiter-berkeley#query:jupiters
• specifies how the rest of the URI is laid out
• Typically protocols

• http(s)
• git
• mailto

• http://www.yelp.com/biz/jupiter-berkeley#query:jupiters

• "Directions" to the resource through hosts and folders

• http://www.yelp.com/biz/jupiter-berkeley#query:jupiters

• "Site" or machine name

• http://www.yelp.com/biz/jupiter-berkeley#query:jupiters

• Similar to directories, but not necessarily linked!
• Groups common resources together

• https://www.google.com/?q=ischool&ref=class

• Starts with ?
• key=value pairs, delimited by &

• https://www.ischool.berkeley.edu:443/index.php

• Specifies a port number to connect to
• Ports are like doorways to a server
• Common ports: 80 for HTTP, 443 for HTTPS

• http://en.wikipedia.org/wiki/URI_scheme#Examples

• http://en.wikipedia.org/wiki/URI_scheme #Examples
• Specify a sub-resource, eg. a section on a page
• Browser will jump to element id

• We've been dealing with .html files so far, what are other types of files?
• What determines a filetype?

• They are specified with a character
• / on Unix & Apple, \ on Windows
• A starting / specifies an "absolute" path

Absolute

Specified from the "root" directory. Doesn't matter which directory you're currently in.

Relative

Directory name is contained in your current directory

• Logical set of data
• To interact with a concept we need to make it real, or have representation of it

• next slide details

• We'll go over how browsers can request the different representations

• http://bearfacts.berkeley.edu/studentlist.xls
• http://bearfacts.berkeley.edu/studentlist.csv
• http://bearfacts.berkeley.edu/studentlist.html
• Bad! all the same resource, should have the same universal resource identifier!
• OK: we know what a resource is. We know what it's representations could be, how do we get those resources and interact with them?

• going over some questions
• We need some way to "link" to another resource! Can't just say "The teacher's slides" which teacher are you talking about? When two people say that in difference classes, are they referring to the same thing?
• Same thing with APIs: {id: 242421}. ID of what? a tweet? review? how do I access it?
• URIs allow us to consistently refer to resources
• Not only that, but a UR L specifically instructs the browser on how to get a representation of the resource.

• TCP is the network layer, which we'll study later
• Basically guarantees that the data we send will either get to the computer or we'll get an error
• Text means you can write out the protocol with your keyboard

• HW sneak peek

• telnet is somehow transferring our keystrokes to another machine…
• Magic! For now. We just assume that what we type gets there, will learn how in a later course

• What resource was it getting?
• What does this remind you of? (HTML)
• Use one method per request

GET

used almost everywhere

PUT

used increasingly by APIs, still limited browser support. Typically will save the representation (eg. in a database)

HEAD

sometimes used for efficiency

DELETE

used increasingly by APIs, still limited browser support

POST

used anytime you want to send data

• GET
• POST
• PUT
• HEAD

• Refer back to Demo
• Flask will use 1.0: it will end the connection on each request
• We will go into the differences in another lecture

• refer to demo
• ischool.berkeley.edu and people.ischool.berkeley.edu could be served off same physical server
• Host header tells the server which we want
• Metadata… remind you of anything? (HTML)