General Computer Science 320201 GenCS I & II Lecture ... - Kwarc

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c○: Michael Kohlhase 355 We will now go through and introduce the infrastructure components of the WWWeb in the order we encounter them. We start with the user agent; in our example the web browser used by the user to request the web page by entering its URL into the URL bar. Web Browsers Definition 526 A web Browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web, enabling users to view Web pages and to jump from one page to another. Practical Browser Tools: Status Bar: security info, page load progress Favorites (bookmarks) View Source: view the code of a Web page Tools/Internet Options, history, temporary Internet files, home page, auto complete, security settings, programs, etc. Example 527 (Common Browsers) MSInternetExplorer is provided by Microsoft for Windows (very common) FireFox is an open source browser for all platforms, it is known for its standards compliance. Safari is provided by Apple for MacOSX and Windows Chrome is a lean and mean browser provided by Google WebKit is a library that forms the open source basis for Safari and Chrome. c○: Michael Kohlhase 356 The web browser communicates with the web server through a specialized protocol, the hypertext transfer protocol, which we cover now. HTTP: Hypertext Transfer Protocol Definition 528 The Hypertext Transfer Protocol (HTTP) is an application layer protocol for distributed, collaborative, hypermedia information systems. June 1999: HTTP/1.1 is defined in RFC 2616 [FGM + 99]. 203
Definition 529 HTTP is used by a client (called user agent) to access web resources (addressed by Uniform Resource Locators (URLs)) via a http request. The web server answers by supplying the resource Most important HTTP requests (5 more less prominent) GET Requests a representation of the specified resource. safe PUT Uploads a representation of the specified resource. idempotent DELETE Deletes the specified resource. idempotent POST Submits data to be processed (e.g., from a web form) to the identified resource. Definition 530 We call a HTTP request safe, iff it does not change the state in the web server. (except for server logs, counters,. . . ; no side effects) Definition 531 We call a HTTP request idempotent, iff executing it twice has the same effect as executing it once. HTTP is a stateless protocol (very memory-efficient for the server.) c○: Michael Kohlhase 357 Finally, we come to the last component, the web server, which is responsible for providing the web page requested by the user. Web Servers Definition 532 A web server is a network program that delivers web pages and supplementary resources to and receives content from user agents via the hypertext transfer protocol. Example 533 (Common Web Servers) apache is an open source web server that serves about 60% of the WWWeb. <strong>II</strong>S is a proprietary server provided by Microsoft. nginx is a lightweight open source web server. Even though web servers are very complex software systems, they come preinstalled on most UNIX systems and can be downloaded for Windows [XAM]. c○: Michael Kohlhase 358 Now that we have seen all the components we fortify our intuition of what actually goes down the net by tracing the http messages. Example: An http request in real life Connect to the web server (port 80) (so that we can see what is happening) telnet www.kwarc.info 80 Send off the GET request GET /teaching/<strong>GenCS</strong>2.html http/1.1 Host: www.kwarc.info User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.4) Gecko/20100413 Firefox/3.6.4 Response from the server HTTP/1.1 200 OK Date: Mon, 03 May 2010 06:48:36 GMT 204
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General Computer Science 320201 Gen
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Java programmer” on the practical
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Contents 1 Preface i 2 Representati
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4 Search and Declarative Computatio
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Fundamental Algorithms and Data str
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To earn an audit you have to take t
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i.e. to function as a member of the
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a factor two in speed. This ability
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“Applets, Not Craplets tm ” (-
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c○: Michael Kohlhase 17 Can be re
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Example 10 (Kruskal’s algorithm,
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n 100n µs 7n 2 µs 2 n µs 1 100
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2.2 Elementary Discrete Math 2.2.1
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Axiom 19 (P 1) “ ” (aka. “zer
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Theorem 36 is a very useful fact to
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Definition 43 The unary product ope
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y stating element-hood (a ∈ S) or
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Idea: We need a notion of “counti
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Example 64 On sets of persons, the
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Definition 82 We say that a set A i
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clean enough to learn important con
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Definition 90 anonymous variables (
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c○: Michael Kohlhase 66 Defining
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- fun both_plus (x:int,y:int) = fn
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+(〈n, o〉) = n (base) and +(〈m
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the axiom says that any object that
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epresent them as a data type, where
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Example 127 〈{N}, {[o: N], [s: N
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The central idea here is what we ha
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Substitutions Definition 149 Let A
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Idea: Well-formed parts of construc
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Other programming languages chose a
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generally: fn+1 := fn + fn−1 plus
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input/output: the interesting bit a
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exception NaN; (* Not a Number *) f
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Example 191 If A = {a, b, c}, then
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Example 210 The Morse Code in the t
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The first 32 characters are control
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Idea: Unicode supports multiple enc
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2.5 Boolean Algebra We will now loo
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What a mess! Iϕ((x1 + x2) + (x1
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c○: Michael Kohlhase 140 The defi
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(f ≤a g), iff there is an n0 ∈
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P.1.2.3 then there are ei ∈ Ebool
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2.5.4 The Quine-McCluskey Algorithm
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the disjunctive normal form, and th
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Proof: by contradiction: let p /∈
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So, the minimal polynomial of f is
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2.6 Propositional Logic 2.6.1 Boole
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Idea: Import semantics from Boolean
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which we can always do, since we ha
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e quite difficult to establish in g
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H 0 axioms are valid Lemma 316 The
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c○: Michael Kohlhase 188 The enta
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The deduction theorem and the entai
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Inference with local hypotheses [A
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2.7 Machine-Oriented Calculi Now we
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Thus the tableau procedure can be u
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A ∨ BT AT BT A ⇒ BT AF BT
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Proof: P.1 It is easy to see tahat
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(P ⇒ Q ⇒ R) ⇒ (P ⇒ Q) ⇒ P
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⎧ ⎪⎨ We represented the maze
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defined a directed graph to be a se
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Paths in Graphs Definition 373 Giv
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This allows us to view Boolean expr
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Computing with Combinational Circui
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Corollary 399 A fully balanced tree
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X 1 X 2 X 3 X n = if L i =X i if L
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3.2 Arithmetic Circuits 3.2.1 Basic
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S S ψ ψ −1 fS = ψ −1 ◦ fT
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The Full Adder Definition 415 The
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first summand 3 4 7 9 8 3 4 7 9 2 s
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c○: Michael Kohlhase 249 The anal
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Problems of Sign-Bit Systems Gener
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generate the n-bit binary number re
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and an + bn + (icn(a, b, c)) = 〈
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Summary: We have built a combinatio
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To understand the operation of the
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Example 443 (Address decoder logic
Page 159 and 160: 3.4 Computing Devices and Programmi
Page 161 and 162: Our notion of time is in this const
Page 163 and 164: instructions LOADIN 1 and LOADIN 2
Page 165 and 166: Definition 457 An ASM program VM is
Page 167 and 168: instruction effect VPC peek i push
Page 169 and 170: c○: Michael Kohlhase 289 With the
Page 171 and 172: Imperative Stack Operations: peek l
Page 173 and 174: A SW program (see the next slide fo
Page 175 and 176: arguments to arithmetic operations
Page 177 and 178: µML, a very simple Functional Prog
Page 179 and 180: call pushes the return address (of
Page 181 and 182: [proc 2 26, con 0, arg 2, leq, cjp
Page 183 and 184: [proc 2 26, con 0, arg 2, leq, cjp
Page 185 and 186: eturn takes the current frame from
Page 187 and 188: label instruction effect comment
Page 189 and 190: Compiling µML Expressions (Continu
Page 191 and 192: c○: Michael Kohlhase 325 We want
Page 193 and 194: State Machine: 1 1,R 1 1,R 1 1,L 1
Page 195 and 196: The coded description acts as a pro
Page 197 and 198: the turing function uses will_halt
Page 199 and 200: Terabyte (T B) 1,000,000,000,000 by
Page 201 and 202: Layers in TCP/IP: TCP/IP uses encap
Page 203 and 204: name comment 4 version IPv4 or IPv6
Page 205 and 206: Domain names must be registered to
Page 207 and 208: That was almost all, but we close t
Page 209: c○: Michael Kohlhase 353 Note tha
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Page 215 and 216: Server-Side Scripting: Programming
Page 217 and 218: c○: Michael Kohlhase 367 Indeed,
Page 219 and 220: presentation tools), but can also i
Page 221 and 222: 1. reads web page 2. reports it hom
Page 223 and 224: Definition 570 Let A be a web page
Page 225 and 226: can combine both to falsify communi
Page 227 and 228: Candidates for one-way/trapdoor fun
Page 229 and 230: on a UNIX system, you can create a
Page 231 and 232: conceptually: transfer of directed
Page 233 and 234: Definition 591 The XML path languag
Page 235 and 236: Resources: Globally Identified by U
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Page 239 and 240: Problem solving Problem: Find algo
Page 241 and 242: Single-state Problem: Start in 5
Page 243 and 244: States integer locations of tiles A
Page 245 and 246: Implementation: States vs. nodes A
Page 247 and 248: Breadth-First Search c○: Michael
Page 249 and 250: Breadth-First Search: Romania c○:
Page 251 and 252: Note: Equivalent to breadth-first s
Page 253 and 254: A B C D E F G H I J K L M N O Depth
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Page 257 and 258: Iterative deepening search Depth-l
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Sibiu 253 Greedy Search: Romania Ar
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P.2 Let n be an unexpanded node on
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A ∗ search: Properties Complete Y
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Definition 618 (n-queens problem) P
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escape certain odd phenomena occurr
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GAs = evolution: e.g., real genes e
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Definition 632 A query is a list of
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(autoload ’run-prolog "prolog" "S
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Example 638 Computing the the n th
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Deduction: knowledge extension Abd
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[Koh06] Michael Kohlhase. OMDoc - A
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astarSearch search, 255 asymmetric-
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infinite, 32 counter program, 152,
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functional variable, 170 gate, 122
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media access control address, 194 M
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procedure abstract, 54 procedure de
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function, 30 spanning tree, 13 spro
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name, 70 variable functional, 170 v
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General Computer Science 320201 GenCS I & II Lecture ... - Kwarc

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