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Search Engine Demystified



Search Engines Demystified. The presentation covers about types of engines, search engine internal, comparative study, indexing, searching, information retrieval, inverted index, clustering, meta ...

Search Engines Demystified. The presentation covers about types of engines, search engine internal, comparative study, indexing, searching, information retrieval, inverted index, clustering, meta search engines, semantic search, search engine optimization, search evaluation, how to do search, search architecture and more.



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  • Go through these procedures fairly quickly: there’s an exercise to learn this You want them to be able to understand the form and what it says. DOMAIN APPROPRIATE FOR THE CONTENT: Do you trust a NYT times article from a personal page as much as one from nytimes.com? A copy of Jackie Onassis’s will from a personal page as much as one from the California Bar Assn.? Example of a personal page would be: www.aol.com/~jbarker They are loosely paralleled by the sequence of the form in the next exercise.
  • You can trust the lii.org more than many referrals. If there are annotations by professionals, that helps. The burden is on you, always. Demonstrate link: search example in Google. Use http://www.hanksville.org/yucatan/mayacal.html

Search Engine Demystified Presentation Transcript

  • 1. Search Engines Sudarsun Santhiappan., M.Tech., Director – R & D, Burning Glass Technologies
  • 2. Today's Coverage
    • Introduction
    • 3. Types of Search Engines
    • 4. Components of a Search Engine
    • 5. Semantics and Relevancy
    • 6. Search Engine Optimization
  • 7. What is a Search Engine ?
    • What is a Search ?
    • 8. Why do we need a Search Engine ?
    • 9. What are we searching against ?
    • 10. How good is a Search Engine ?
    • 11. What is Search on Search (Meta SE) ?
    • 12. Compared Search Engines Side-by-Side ?
    • 13. How are Images and Videos searched ?
    • 14. Apart from Web Search, what else ?
  • 15. Introduction
    • Web Search Engine is a software program that searches the Internet (bunch of websites) based on the words that you designate as search terms (query words).
    • 16. Search engines look through their own databases of information in order to find what it is that you are looking for.
    • 17. Web Search Engines are a good example for massively sized Information Retrieval Systems.
      • Tried “Similar pages” Link in Google result set ?
  • 18. Dictionary Definitions Search COMPUTING ( transitive verb ) to examine a computer file, disk, database, or network for particular information Engine something that supplies the driving force or energy to a movement, system, or trend Search Engine a computer program that searches for particular keywords and returns a list of documents in which they were found, especially a commercial service that scans documents on the Internet
  • 19. About definition of search engines
    • oh well … search engines do not search only for keywords, some search for other stuff as well
    • 20. and they are really not “engines” in the classical sense
      • but then mouse is not a “mouse”
  • 21. use of search engines … among others
  • 22. Types of Search Engines
    • Text Search Engines
      • General: AltaVista, AskJeeves, Bing, Google
      • 23. Specialized: Google Scholar, Scirus, Citeseer
    • Intranet vs Internet Search Engines
    • 24. Image Search Engines
      • How can we search on the Image content ?
    • Video Search Engines
      • Image Search with Time dimension !!
  • 25. Types of Search Engine
    • Crawler Powered Indexes
      • Guruji.com, Google.com
    • Human Powered Indexes
      • www.dmoz.org
    • Hybrid Models
      • Submitted URLs to a search engine ?
    • Semantic Indexes
      • Hakia.com,
  • 26. Have you tried Hakia ?
    • What is Semantic Search ?
    • 27. How's it different from Keyword Search?
    • 28. What is categorized search ?
    • 29. Side-by-Side comparison with Google!!
    • 30. Have you compared Bing with Google ?
  • 31.  
  • 32.  
  • 33. Directories
    • www.dmoz.org
    • 34. Website classified into a Taxonomy
    • 35. Website are categorically arranged
    • 36. Searching vs Navigation
    • 37. Instead of Query, you Click and navigate
    • 38. Accurate search always! (if data is available)
    • 39. Problem: Mostly Manually created
  • 40.  
  • 41.  
  • 42. How does a Search Engine work ?
  • 43. How Search Engines Work (Sherman 2003) Your Browser The Web URL1 URL2 URL3 URL4 Crawler Indexer Search Engine Database Eggs? Eggs. Eggs - 90% Eggo - 81% Ego- 40% Huh? - 10% All About Eggs by S. I. Am
  • 44. how do search engines work? elaboration
    • crawlers, spiders : go out to find content
      • in various ways go through the web looking for new & changed sites
      • 45. periodic, not for each query
        • no search engine works in real time
      • some search engines do it for themselves, others not
        • buy content from companies such as Inktomi
      • for a number of reasons crawlers do not cover all of the web – just a fraction
      • 46. what is not covered is “invisible web” ?
  • 47. Elaboration …
    • organizing content: labeling, arranging
      • indexing for searching – automatic
        • keywords and other fields
        • 48. arranging by URL popularity - PageRank as Google
      • classifying as directory
        • mostly human handpicked & classified
    • as a result of different organization we have basically two kinds of search engines:
        • search – input is a query that is searched & displayed
        • 49. directory – classified content – a class is displayed
          • and fused: directories have search capabilities & vice versa
  • 50. Elaboration (cont.)
    • databases, caches: storing content
      • humongous files usually distributed over many computers
    • query processor: searching, retrieval, display
      • takes your query as input
        • engines have differing rules on how they are handled
      • displays ranked output
        • some engines also cluster output and provide visualization
        • 51. some engines provide categorically structured results
    • at the other end is your browser
  • 52. Similarities & Differences
    • All search engines have these basic parts in common
    • 53. BUT the actual processes – methods how they do it – are based on various algorithms and they significantly differ
      • most are proprietary (patented) with details kept mostly secret (or protected) but based on well known principles from information retrieval or classification
      • 54. to some extent Google is an exception – they published their method
  • 55. Google Search
    • In the beginning it ran on Stanford computers
    • 56. Basic approach has been described in their famous paper “The Anatomy of a Large-Scale Hypertextual Web Search Engine”
      • well written, simple language, has their pictures
      • 57. in acknowledgement they cite the support by NSF’s Digital Library Initiative i.e. initially, Google came out of government sponsored research
      • 58. describe their method PageRank - based on ranking hyperlinks as in citation indexing
      • 59. “ We chose our system name, Google, because it is a common spelling of googol, or ten on hundredth power”
  • 60. coverage differences
    • no engine covers more than a fraction of WWW
      • estimates: none more than 16%
      • 61. hard (even impossible) to discern & compare coverage, but they differ substantially in what they cover
    • in addition:
      • many national search engines
        • own coverage, orientation, governance
      • many specialized or domain search engines
        • own coverage geared to subject of interest
      • many comprehensive sources independent of search engines
        • some have compilations of evaluated web sources
  • 62. searching differences
    • substantial differences among search engines on searching, retrieval display
      • need to know how they work & differ in respect to
        • defaults in searching a query
        • 63. searching of phrases, case sensitivity, categories
        • 64. searching of different fields, formats, types of resources
        • 65. advance search capabilities and features
        • 66. possibilities for refinement, using relevance feedback
        • 67. display options
        • 68. personalization options
  • 69.  
  • 70.  
  • 71. Limitations
    • every search engine has limitation as to
      • Coverage: meta engines just follow coverage limitations & have more of their own search capabilities
      • 72. finding quality information
    • some have compromised search with economics
      • becoming little more than advertisers
    • but search engines are also many times victims of spamdexing
      • affecting what is included and how ranked
  • 73. Spamming a search engine
    • use of techniques that push rankings higher than they belong is also called spamdexing
      • methods typically include textual as well as link-based techniques
      • 74. like e-mail spam, search engine spam is a form of adversarial information retrieval
        • the conflicting goals of accurate results of search providers & high positioning by content page rank
  • 75. Meta Search Engines Search on Search
  • 76. Meta search engines
    • meta engines search multiple engines
      • getting combined results from a variety of engines
    • do not have their own databases
      • but have their own business models affecting results
    • a number of techniques used
      • interesting ones: clustering, statistical analysis
  • 77. Some Meta engines - with organized results Dogpile : results from a number of leading search engines; gives source, so overlap can be compared; (has also a (bad) joke of the day) Surfwax : gives statistics and text sources & linking to sources; for some terms gives related terms to focus Teoma : results with suggestions for narrowing; links resources derived; originated at Rutgers Turbo10 : provides results in clusters; engines searched can be edited
  • 78.  
  • 79.  
  • 80. Some Meta Engines (cont.)
    • Large directory
      • Complete Planet
      • directory of over 70,000 databases & specialty engines
    • Results with graphical displays
      • Vivisimo clusters results; innovative
      • 81. Webbrain results in tree structure – fun to use
      • 82. Kartoo results in display by topics of query
  • 83. Domain Specific Search Engines
  • 84. Domain Search Engines & Catalogs
    • cover specific subjects & topics
    • 85. important tool for subject searches
      • particularly for subject specialist
      • 86. valued by professional searchers
    • selection mostly hand-picked rather than by crawlers, following inclusion criteria
      • often not readily discernable
      • 87. but content more trustworthy
  • 88. Domain Search Engines … Open Directory Project
        • large edited catalog of the web – global, run by volunteers
        • selected Internet resources covering all academic subject areas; organized by Dewey Decimal System – from UK
    Profusion search in categories for resources & search engines Resource Discovery Network – UK “ UK's free national gateway to Internet resources for the learning, teaching and research community”
  • 89. Domain Engines … sample Think Quest – Oracle Education Foundation
    • education resources, programs; web sites created by students
    All Music Guide
    • resource about musicians, albums, and songs
    Internet Movie Database
    • treasure trove of American and British movies
    Genealogy links and surname search engines well.. that is getting really specialized (and popular) Daypop searches the “living web” “The living web is composed of sites that update on a daily basis: newspapers, online magazines, and weblogs”
  • 90. Science, scholarship engines …sample
      • Psychcrawler - Amer Psychological Association
        • web index for psychology
      • Entrez PubMed – Nat Library of Medicine
    biomedical literature from MEDLINE & health journals
      • CiteSeer - NEC Research Center
        • scientific literature, citations index; strong in computer science
    Scholar Google searches for scholarly articles & resources Infomine scholarly internet research collections Scirus scientific information in journals & on the web
  • 91. Science, scholarship engines …sample commercial access
    • an addition to freely accessible engines many provide search free but access to full text paid
      • by subscription or per item
      • 92. RUL provides access to these & many more:
    ScienceDirect Elsevier: “world's largest electronic collection of science, technology and medicine full text and bibliographic information” ACM Portal Association for Computing Machinery: access to ACM Digital Library & Guide to Computing
  • 93. Search Engine Internals
  • 94. Search Engine Internals
    • Crawlers
    • 95. Indexers
    • 96. Searching
    • 97. Semantics
    • 98. Ranking
  • 99. Standard Web Search Engine Architecture crawl the web create an inverted index Check for duplicates, store the documents Inverted index Search engine servers user query Show results To user DocIds
  • 100. Typical Search Engine
  • 101.  
  • 102.  
  • 103. Crawlers
    • What is Crawling ?
    • 104. How does Crawling happen ?
    • 105. Have you tried “wget -r <url>” in Linux ?
    • 106. Have you tried “DAP” to download entire site?
    • 107. Page Walk
    • 108. Spidering & Crawlbots
  • 109.  
  • 110.  
  • 111. Spidering the Web
    • Replicating the Spider's behavior of building the Internet (web) by adding spirals (sites)
    • 112. But, can the web be fully crawled ?
    • 113. By the time, one round of indexing is over, the page might have changed already!
    • 114. That's why we have cached page link in the search result!
  • 115.  
  • 116. Crawler Bots
    • How to make your website Crawlable ?
    • 117. White-listing and Black-listing!
    • 118. Meta Tags to control the Bots
    • 119. Can HTTPS pages be crawled ?
    • 120. Does Sessions maintained while crawling ?
    • 121. Can dynamic pages be crawled ?
    • 122. URL normalization
      • cool.com?page=2 [crawler unfriendly]
      • 123. cool.com/page/2 [norm'd and crawler friendly]
  • 124. How to control Robots ? <HTML> <HEAD> <META NAME=&quot;ROBOTS&quot; CONTENT=&quot; NOINDEX,NOFOLLOW &quot;> <TITLE>...</TITLE> </HEAD> <BODY> Index : This tell the spider/bot that it’s OK to index this page Noindex : Spider/bot see this and don’t index any of the content on this page. Follow : This let the spider/bot know that it’s OK to travel down links found on this page. Nofollow : It tells the spider/bot not to follow any of the links on this page.
  • 125. Crawling – Process Flow
  • 126. Data Structures
    • Tree primarily while Crawling
    • 127. Both Depth-First-Search and Breadth-First-Search are used
    • 128. Every page that the crawler visits shall be added as a node to the Tree
    • 129. Fan-out information is represented as Children for a node (page).
  • 130. Inverted Indexes the IR Way
  • 131. How Inverted Files Are Created
    • Periodically rebuilt, static otherwise.
    • 132. Documents are parsed to extract tokens. These are saved with the Document ID.
    Now is the time for all good men to come to the aid of their country Doc 1 It was a dark and stormy night in the country manor. The time was past midnight Doc 2
  • 133. How Inverted Files are Created
    • After all documents have been parsed the inverted file is sorted alphabetically.
  • 134. How Inverted Files are Created
    • Multiple term entries for a single document are merged.
    • 135. Within-document term frequency information is compiled.
  • 136. How Inverted Files are Created
    • Finally, the file can be split into
      • A Dictionary or Lexicon file
      • A Postings file
  • 137. How Inverted Files are Created Dictionary/Lexicon Postings
  • 138. Inverted indexes
    • Permit fast search for individual terms
    • 139. For each term, you get a list consisting of:
      • document ID
      • 140. frequency of term in doc (optional)
      • 141. position of term in doc (optional)
    • These lists can be used to solve Boolean queries:
        • country -> d1, d2
        • 142. manor -> d2
        • 143. country AND manor -> d2
    • Also used for statistical ranking algorithms
  • 144. Inverted Indexes for Web Search Engines
    • Inverted indexes are still used, even though the web is so huge.
    • 145. Some systems partition the indexes across different machines. Each machine handles different parts of the data.
    • 146. Other systems duplicate the data across many machines; queries are distributed among the machines.
    • 147. Most do a combination of these.
  • 148. From description of the FAST search engine, by Knut Risvik In this example, the data for the pages is partitioned across machines. Additionally, each partition is allocated multiple machines to handle the queries. Each row can handle 120 queries per second Each column can handle 7M pages To handle more queries, add another row.
  • 149. Cascading Allocation of CPUs
    • A variation on this that produces a cost-savings:
      • Put high-quality/common pages on many machines
      • 150. Put lower quality/less common pages on fewer machines
      • 151. Query goes to high quality machines first
      • 152. If no hits found there, go to other machines
  • 153. The Search Process
  • 154. Searching – Process Flow
  • 155. Google Query Evaluation
    • Parse the Query
    • 156. Convert words to WordID
    • 157. Seek to the start of the doclist in the short barrel for every word.
    • 158. Scan through the doclists until there is a document that matches all the search terms.
    • 159. Compute the rank of that document for the query.
    • 160. If we are in the short barrels and at the end of any doclist, seek to the start of the doclist in the full barrel for every word and go to step 4.
    • 161. If we are not at the end of any doclist go to step 4.
    • 162. Sort the documents that have matched by rank and return the top k.
  • 163. Queries
    • Search engines are one tool used to answer info needs
    • 164. Users express their information needs as queries
    • 165. Usually informally expressed as two or three words (we call this a ranked query )
    • 166. A recent study showed the mean query length was 2.4 words per query with a median of 2
    • 167. Around 48.4% of users submit just one query in a session, 20.8% submit two, and about 31% submit three or more
    • 168. Less than 5% of queries use Boolean operators (AND, OR, and NOT), and around 5% contain quoted phrases
  • 169. Queries...
    • About 1.28 million different words were used in queries in the Excite log studied (which contained 1.03 million queries)
    • 170. Around 75 words account for 9% of all words used in queries. The top-ten non-trivial words occurring in 531,000 queries are “ sex ” (10,757), “ free ” (9,710), “ nude ” (7,047), “ pictures ” (5,939), “ university ” (4,383), “ pics ” (3,815), “ chat ” (3,515), “ adult ” (3,385), “ women ” (3,211), and “ new ” (3,109)
    • 171. 16.9% of the queries were about entertainment , 16.8% about sex, pornography, or preferences , and 13.3% concerned commerce, travel, employment, and the economy
  • 172. Answers What is a good answer to a query?
    • One that is relevant to the user’s information need!
    • 173. Search engines typically return ten answers-per-page, where each answer is a short summary of a web document
    • 174. Likely relevance to an information need is approximated by statistical similarity between web documents and the query
    • 175. Users favour search engines that have high precision , that is, those that return relevant answers in the first page of results
  • 176. Approximating Relevance
    • Statistical similarity is used to estimate the relevance of a query to an answer
    • 177. Consider the query “ Richardson Richmond Football ”
    • 178. A good answer contains all three words, and the more frequently the better; we call this term frequency (TF)
    • 179. Some query terms are more important—have better discriminating power—than others. For example, an answer containing only “ Richardson ” is likely to be better than an answer containing only “ Football ”; we call this inverse document frequency (IDF)
  • 180. Ranking To improve the accuracy of search engines:
    • Google Inc. use their patented Pa geRank(tm) technology. Google ranks a page higher if it links to pages that are an authorative source, and a link from an authorative source to a page ranks that page higher
    • 181. Relevance feedback is a technique that adds words to a query based on a user selecting a more like this option
    • 182. Query expansion adds words to a query using thesaural or other techniques
    • 183. Searching within categories or groups to narrow a search
  • 184. Resolving Queries
    • Queries are resolved using the inverted index
    • 185. Consider the example query “ Cat Mat Hat ”. This is evaluated as follows:
      • Select a word from the query (say, “ Cat ”)
      • 186. Retrieve the inverted list from disk for the word
      • 187. Process the list. For each document the word occurs in, add weight to an accumulator for that document based on the TF, IDF, and document length
      • 188. Repeat for each word in the query
      • 189. Find the best-ranked documents with the highest weights
      • 190. Lookup the document in the mapping table
      • 191. Retrieve and summarize the docs, and present to the user
  • 192. Fast Search Engines
    • Inverted lists are stored in a compressed format. This allows more information per second to be retrieved from disk, and it lowers disk head seek times
    • 193. As long as decompression is fast, there is a beneficial trade-off in time
    • 194. Documents are stored in a compressed format for the same reason
    • 195. Different compression schemes are used for lists (which are integers) and documents (which are multimedia, but mostly text)
  • 196. Fast Search Engines
    • Sort disk accesses to minimise disk head movement when retrieving lists or documents
    • 197. Use hash tables in memory to store the vocabulary; avoid slow hash functions that use modulo
    • 198. Pre-calculate and store constants in ranking formulae
    • 199. Carefully choose integer compression schemes
    • 200. Organise inverted lists so that the information frequently needed is at the start of the list
    • 201. Use heap structures when partial sorting is required
    • 202. Develop a query plan for each query
  • 203. Search Engine Architecture
  • 204. Search Engine architecture
    • The inverted lists are divided amongst a number of servers, where each is known as a shard
    • 205. If an inverted list is required for a particular range of words, then that shard server is contacted
    • 206. Each shard server can be replicated as many times as required; each server in a shard is identical
    • 207. Documents are also divided amongst a number of servers
    • 208. Again, if a document is required within a particular range, then the appropriate document server is contacted
    • 209. Each document server can also be replicated as many times as required
  • 210. Google, Case Study
  • 211. Google Architecture
  • 212. Components
    • URL Server: Bunch of URLs (white-list)
    • 213. Crawler: Fetch the page
    • 214. Store Server: To store the fetched pages
    • 215. Repository: Compressed pages are put here
    • 216. Every unique page has a DocID
    • 217. Anchor: Page transition [to, from] information
    • 218. URLResolver: Relative URL to Absolute URL
    • 219. Lexicon: list of known words
  • 220. Indexer
    • Parses the document
    • 221. Build Word-Frequency table {word, position, font, capitalization} [hits]
    • 222. Pushes the hits to barrels as partially sorted forward index
    • 223. Identifies anchors (page transition out info)
  • 224. Searcher
    • Forward Index to Inverted Index
      • Maps keywords to DocIds
      • 225. DocIds mapped to URLs
    • Reranker
      • Uses Anchor information to rank the pages for the given query keyword.
      • 226. Thumbrule: Fan In increases page rank
  • 227. Reranking
  • 228. What about Ranking?
    • Lots of variation here
      • Often messy; details proprietary and fluctuating
    • Combining subsets of:
      • IR-style relevance: Based on term frequencies, proximities, position (e.g., in title), font, etc.
      • 229. Popularity information
      • 230. Link analysis information
    • Most use a variant of vector space ranking to combine these. Here’s how it might work:
      • Make a vector of weights for each feature
      • 231. Multiply this by the counts for each feature
  • 232. Relevance: Going Beyond IR
    • Page “popularity” (e.g., DirectHit)
      • Frequently visited pages (in general)
      • 233. Frequently visited pages as a result of a query
    • Link “co-citation” (e.g., Google)
      • Which sites are linked to by other sites?
      • 234. Draws upon sociology research on bibliographic citations to identify “authoritative sources”
  • 235. Link Analysis for Ranking Pages
    • Assumption: If the pages pointing to this page are good, then this is also a good page.
        • References: Kleinberg 98, Page et al. 98
    • Draws upon earlier research in sociology and bibliometrics.
      • Kleinberg’s model includes “authorities” (highly referenced pages) and “hubs” (pages containing good reference lists).
      • 236. Google model is a version with no hubs, and is closely related to work on influence weights by Pinski-Narin (1976).
  • 237. Link Analysis for Ranking Pages
    • Why does this work?
      • The official Toyota site will be linked to by lots of other official (or high-quality) sites
      • 238. The best Toyota fan-club site probably also has many links pointing to it
      • 239. Less high-quality sites do not have as many high-quality sites linking to them
  • 240. PageRank
    • Let A1, A2, …, An be the pages that point to page A. Let C(P) be the # links out of page P. The PageRank (PR) of page A is defined as:
    • 241. PageRank is principal eigenvector of the link matrix of the web.
    • 242. Can be computed as the fixpoint of the above equation.
    PR(A) = (1-d) + d ( PR(A1)/C(A1) + … + PR(An)/C(An) )
  • 243. PageRank: User Model
    • PageRanks form a probability distribution over web pages: sum of all pages’ ranks is one.
    • 244. User model: “Random surfer” selects a page, keeps clicking links (never “back”), until “bored”: then randomly selects another page and continues.
      • PageRank(A) is the probability that such a user visits A
      • 245. d is the probability of getting bored at a page
    • Google computes relevance of a page for a given search by first computing an IR relevance and then modifying that by taking into account PageRank for the top pages.
  • 246. Search Engine Optimization
  • 247.
    • Location, Location, Location...and Frequency
    • 248. Tags (<title>, <meta>, <b>, top of the page)
    • 249. How close words (from the query) are to each other on the website
    • 250. Quality of links going to and from a page
    • 251. Penalization for &quot;spamming“, when a word is repeated hundreds of times on a page, to increase the frequency and propel the page higher in the listings.
    • 252. Off the Page ranking criteria:
        • By analyzing how pages link to each other.
    How Search Engines Rank Pages?
  • 253. Why do results differ ?
    • Some search engines index more web pages than others.
    • 254. Some search engines also index web pages more often than others.
    • 255. The result is that no search engine has the exact same collection of web pages to search through.
    • 256. Different algorithms to compute relevance of the page to a particular query
  • 257. Search Engine Placement Tips
    • Why is it important to be on the first page of the results?
      • Most users do not go beyond the first page.
    • How to optimize your website?
      • Pick your target keywords: How do you think people will search for your web page? The words you imagine them typing into the search box are your target keywords.
      • 258. Pick target words differently for each page on your website.
      • 259. Your target keywords should always be at least two or more words long.
  • 260. Position your Keywords
    • Make sure your target keywords appear in the crucial locations on your web pages. The page's HTML <title> tag is most important.
    • 261. The titles should be relatively short and attractive. Several phrases are enough for the description.
    • 262. Search engines also like pages where keywords appear &quot;high&quot; on the page: headline, first paragraphs of your web page.
    • 263. Keep in mind that tables and large JavaScript sections can make your keywords less relevant because they appear lower on the page.
  • 264. Have Relevant Content
    • Keywords need to be reflected in the page's content.
    • 265. Put more text than graphics on a page
    • 266. Don't use frames
    • 267. Use the <ALT….> tag
    • 268. Make good use of <TITLE> and <H1>
    • 269. Consider using the <META> tag
    • 270. Get people to link to your page
  • 271. Hiding Web pages
    • You may wish to have web pages that are not indexed (for example, test pages).
    • 272. It is also possible to hide web content from robots, using the Robots.txt file and the robots meta tag.
    • 273. Not all crawlers will obey this, so this is not foolproof.
  • 274. Submitting To Search Engines
    • Search engines should find you naturally, but submitting helps speed the process and can increase your representation
    • 275. Look for Add URL link at bottom of home page
    • 276. Submit your home page and a few key “section” pages
    • 277. Turnaround from a few days to 2 months
  • 278. Deep Crawlers
    • AltaVista, Inktomi, Northern Light will add the most, usually within a month
    • 279. Excite, Go (Infoseek) will gather a fair amount; Lycos gathers little
    • 280. Index sizes are going up, but the web is outpacing them…nor is size everything
    • 281. Here are more actions to help even the odds…
  • 282. “ Deep” Submit
    • A “deep” submit is directly submitting pages from “inside” the web site – can help improve the odds these will get listed.
    • 283. At Go, you can email hundreds of URLs. Consider doing this.
    • 284. At HotBot/Inktomi, you can submit up to 50 pages per day. Possibly worth doing.
    • 285. At AltaVista, you can submit up to 5 pages per day. Probably not worth the effort.
    • 286. Elsewhere, not worth doing a “deep” submit.
  • 287. Big Site? Split It Up
    • Expect search engines to max out at around 500 pages from any particular site
    • 288. Increase representation by subdividing large sites logically into subdomains
      • Search engines will crawl each subsite to more depth
    • Here’s an example...
  • 289. Subdomains vs. Subdirectories
  • 290. I Was Framed
    • Don't use them. Period.
    • 291. If you do use them, search engines will have difficulty crawling your site.
  • 292. Dynamic Roadblocks
    • Dynamic delivery systems that use ? symbols in the URL string prevent search engines from getting to your pages
      • http://www. nike .com/ ObjectBuilder / ObjectBuilder . iwx ? ProcessName = IndexPage &Section_Id=17200& NewApplication =t
    • Eliminate the ? symbol, and your life will be rosy
    • 293. Look for workarounds, such as Apache rewrite or Cold Fusion alternatives
    • 294. Before you move to a dynamic delivery system, check out any potential problems.
  • 295. How Directories Work
    • Editors find sites, describe them, put them in a category
    • 296. Site owners can also submit to be listed
    • 297. A short description represents the entire web site
    • 298. Usually has secondary results from a crawler-based search engine
  • 299. The Major Directories
    • Yahoo
    • 300. The Open Directory
      • (Netscape, Lycos, AOL Search, others)
    • LookSmart
    • 301. UK Plus
    • 302. Snap
  • 303. Submitting To Directories
    • Directories probably won't find you or may list you badly unless you submit
    • 304. Find the right category (more in a moment), then use Add URL link at top or bottom of page
    • 305. Write down who submitted (and email address), when submitted, which category submitted to and other details
      • You’ll need this info for the inevitable resubmission attempt – it will save you time.
  • 306. Submitting To Directories
    • Take your time and submit to these right
    • 307. Write 3 descriptions: 15, 20 and 25 words long, which incorporate your key terms
    • 308. Search for the most important term you want to be found for and submit to first category that's listed which seems appropriate for your site
    • 309. Be sure to note the contact name and email address you provided on the submit form
    • 310. If you don't get in, keep trying
  • 311. Subdomain Advantage
    • Directories tend not to list subsections of a web site.
    • 312. In contrast, they do tend to see subdomains as independent web sites deserving their own listings
    • 313. So, another reason to go with subdomains over subdirectories
  • 314. How to do Search ?
  • 315. What do we search ?
    • Information
    • 316. Reviews, news
    • 317. Advice, methods
    • 318. Bugs
    • 319. Education stuff
    • 320. Examples:
      • Access Violation 0xC0000005
      • 321. Search Engine ppt
  • 322.  
  • 323. Main Steps
    • Make a decision about the search
    • 324. Formulate a topic. Define a type of resources that you are looking for
    • 325. Find relevant words for description
    • 326. Find websites with information
    • 327. Choose the best out of them
    • 328. Feedback: How did you search?
  • 329. Main Problems Why is it difficult to search?
      • Know the problem, don’t know what to look for
      • 330. Lose focus (go to interesting but non-relevant sites)
      • 331. Perform superficial (shallow) search
      • 332. Search Spam
  • 333. Typical Problems
    • Links are often out of date
    • 334. Usually too many links are returned
    • 335. Returned links are not very relevant
    • 336. The Engines don't know about enough pages
    • 337. Different engines return different results
    • 338. Political bias
  • 339. Typical Mistakes
    • Unnecessary words in a query
    • 340. Unsuitable choice of keywords
    • 341. Not enough flexibility in changing keywords (Ses)
    • 342. Divide the time devoted to search and evaluation of search results
    • 343. “ Your search did not match any documents. ” – Bad Query!
  • 344. Search Tricks What can we search for?
    • Thematic resource ( http://www.topicmaps.org )
    • 345. Community
    • 346. Collection of articles
    • 347. Forum
    • 348. Catalog of resources, links
    • 349. File (file types)
    • 350. Encyclopedia article
    • 351. Digital library
    • 352. Contact information (i.e. email)
  • 353. Improving Query Results
    • To look for a particular page use an unusual phrase you know is on that page
    • 354. Use phrase queries where possible
    • 355. Check your spelling!
    • 356. Progressively use more terms
    • 357. If you don't find what you want, use another Search Engine!
  • 358. Useful words
    • download
    • 359. pdf, ppt, doc, zip, mp3
    • 360. forum, directory, links
    • 361. faq, for newbies, for beginners, guide, rules, checklist
    • 362. lecture notes, survey, tutorials
    • 363. how, where, correct, howto
    • 364. Copy-pasting the exact error message
    • 365. Have you tried http://del.icio.us/ ?
  • 366. Search Engine Features
  • 367. Features
    • Indexing features
    • 368. Search features
    • 369. Results display
    • 370. Costs, licensing and registration requirements
    • 371. Unique features (if any)
  • 372. Indexing Features
    • File/document formats supported: HTML, ASCII, PDF, SQL, Spread Sheets, WYSIWYG (MS-Word, WP, etc.)
    • 373. Indexing level support: File/directory level, multi-record files
    • 374. Standard formats recognized: MARC, Medline, etc
    • 375. Customization of document formats
      • Stemming: If yes, is this an optional or mandatory feature?
      • 376. Stop words support: If yes, is this an optional or mandatory features ?
  • 377. Searching Features
    • Boolean Searching: Use of Boolean operators AND, OR and NOT as search term connectors
    • 378. Natural Language: Allows users to enter the query in natural language
    • 379. Phrase: Users can search for exact phrase
    • 380. Truncation/wild card: Variations of search terms and plural forms can be searched
    • 381. Exact match: Allows users to search for terms exactly as it is entered
    • 382. Duplicate detection: Remove duplicate records from the retrieved records
    • 383. Proximity: With connectors such as With , Near, ADJacent one can specify the position of a search terms w.r.t to others
  • 384. Searching Features
    • Field Searching: Query for a specific field value in the database
    • 385. Thesaurus searching: Search for Broader or Narrower or Related terms or Related concepts
    • 386. Query by example: Enables users to search for similar documents
    • 387. Soundex searching: Search for records with similar spelling as the search term
    • 388. Relevance ranking: Ranking the retrieved records in some order
    • 389. Search set manipulation: Saving the search results as sets and allowing users to view search history
  • 390. Results Display
    • Formats supported: Can it display in native format or just HTML; Display in different formats, Display number of records retrieved
    • 391. Relevancy ranking: If the retrieved records are ranked, how the relevance score is indicated
    • 392. Keyword-in-context: KWIC or highlighting of matching search terms
    • 393. Customization of results display: allow users to select different display formats
    • 394. Saving options: Saving in different formats; number of records that can be saved at a time
  • 395. Evaluation of Search Engines
  • 396. CRITICAL EVALUATION Why Evaluate What You Find on the Web?
    • Anyone can put up a Web page
      • about anything
    • Many pages not kept up-to-date
    • 397. No quality control
      • most sites not “peer-reviewed”
        • less trustworthy than scholarly publications
      • no selection guidelines for search engines
  • 398. Web Evaluation Techniques Before you click to view the page...
    • Look at the URL - personal page or site ? ~ or % or users or members
    • 399. Domain name appropriate for the content ? edu, com, org, net, gov, ca.us, uk, etc.
    • 400. Published by an entity that makes sense ?
        • News from its source?
        • Advice from valid agency?
    www.nih.gov/ www.nlm.nih.gov/ www.nimh.nih.gov/
  • 401. Web Evaluation Techniques Scan the perimeter of the page
    • Can you tell who wrote it ?
        • name of page author
        • 402. organization, institution, agency you recognize
        • 403. e-mail contact by itself not enough
    • Credentials for the subject matter ?
      • Look for links to:
    “ About us” “Philosophy” “Background” “Biography”
    • Is it recent or current enough ?
        • Look for “last updated” date - usually at bottom
    • If no links or other clues...
        • truncate back the URL
  • 404. Web Evaluation Techniques Indicators of quality
    • Sources documented
        • links, footnotes, etc.
          • As detailed as you expect in print publications ?
        • do the links work ?
    • Information retyped or forged
        • why not a link to published version instead ?
    • Links to other resources
        • biased, slanted ?
  • 405. Web Evaluation Techniques What Do Others Say ?
    • Search the URL in alexa.com
      • Who links to the site? Who owns the domain?
      • 406. Type or paste the URL into the basic search box
      • 407. Traffic for top 100,000 sites
    • See what links are in Google’s Similar pages
    • 408. Look up the page author in Google
  • 409.  
  • 410. Web Evaluation Techniques STEP BACK & ASK: Does it all add up ?
    • Why was the page put on the Web ?
        • inform with facts and data?
        • 411. explain, persuade?
        • 412. sell, entice?
        • 413. share, disclose?
        • 414. as a parody or satire?
    • Is it appropriate for your purpose?
  • 415. Try evaluating some sites... Search a controversial topic in Google:
      • &quot;nuclear armageddon&quot;
      • 416. prions danger
      • 417. “ stem cells” abortion
    Scan the first two pages of results Visit one or two sites
      • try to evaluate their quality and reliability
  • 418. Ufff, The End
    • Have you learned something today ?
    • 419. Try whatever we've discussed today!
    • 420. If you need help, let me know at [email_address]