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Best Practices for Search

Best Practices for Search. for the Federal Government Marti Hearst Web Manager University November 10, 2009. The Importance of Search for Govt. OMB memorandum, Dec 2005: “When disseminating information to the public-at-large, publish your information directly to the internet.”

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Best Practices for Search

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  1. Best Practices for Search for the Federal Government Marti Hearst Web Manager University November 10, 2009

  2. The Importance of Search for Govt • OMB memorandum, Dec 2005: “When disseminating information to the public-at-large, publish your information directly to the internet.” • Pres. Obama’s memorandum, Jan 21, 2009: “Information maintained by the Federal Government is a national asset. My Administration will take appropriate action, consistent with law and policy, to disclose information rapidly in forms that the public can readily find and use. ”

  3. A bit about me • Professor at the School of Information at University of California, Berkeley. • Teach masters students • User Interface Design, Search Engines, Computational Linguistics, Visualization. • Search User Interfaces • Visiting government for 1 year • Updating usasearch.gov • Looking at site search alternatives. • Generally kibbitzing

  4. Two Focus Areas • Web search engines • The quality and form of your content • How your results are viewed in search engine listings • How your site is crawled • Site search • The search interface • What is crawled • How results are presented

  5. Outline • Designing your site for effective search • Site search interfaces • Special considerations for web search engines • An example of what not to do.

  6. both content and tech people • have to be focused on it together • mention why using (free) book example • add an exercise towards the start • top 3 things to do right away • don’t force h1n1, be sure swine flu too • seo integrated into process

  7. Use Proven Interface Techniques • Use modern search UI ideas that are known to have good usability. • Apply the principle: recognition over recall. • Related query suggestions • Auto-suggest as the user types • Use faceted navigation where appropriate.

  8. Search-as-you-Type (SAYT) • As the user types, shows other peoples’ queries with the same word stems. • Helps people think of additional words • (recognition over recall) • Proven to improve search results.

  9. Evidence-based Decision Making DATA TRUMPS INTUITIONS (Kohavi)

  10. Use Evidence-based Decision Making User behavior determines if an idea is retained. A/B testing is a standard way to do this. • Make small changes to an interface. • Show the changed interface to a significant sample of the user population, show everyone else the original version. • Do this over time (~ two weeks) and for (tens of) thousands of users. • Compare what the two groups do over time. • Based on this, decide whether to keep or reject the feature.

  11. Evidence-based Decision Making • Example: • Dan Siroker on Obama for America’s website and video design decisions • Easy to measure the outcome: it is in money donated. • http://www.siroker.com/archives/2009/05/14/obama_lessons_learned_talk_at_google.html

  12. Vote: Which Button is Best? count down counter

  13. Which Button is Best?

  14. Which Button is Best?

  15. Ease of Use: Summary USE PROVEN UI TECHNIQUES REDUCE EXTRA STEPS USE CLEAR LANGUAGE MAKE EVIDENCE-BASED UI DECISIONS

  16. How Web Search Engines Work

  17. How Search Engines Work Three main parts: • Gather the contents of all web pages (crawling) • Organize the contents of the pages in a way that allows efficient retrieval (indexing) • Take in a query, determine which pages match, and show the results (ranking and display of results)

  18. Standard Web Search Engine Architecture user query

  19. Standard Web Search Engine Architecture Check for duplicates, store the documents DocIds crawl the web Crawler machines Create an inverted index Inverted index Search engine servers

  20. Standard Web Search Engine Architecture Check for duplicates, store the documents DocIds crawl the web Crawler machines Create an inverted index user query Inverted index Search engine servers Show results To user

  21. Spiders or crawlers • How to find web pages to visit and copy? • Can start with a list of domain names, visit the home pages there. • Look at the hyperlink on the home page, and follow those links to more pages. • Keep a list of urls visited, and those still to be visited. • Each time the program loads in a new HTML page, add the links in that page to the list to be crawled.

  22. Spider behaviour varies • Parts of a web page that are indexed • How deeply a site is indexed • Types of files indexed • How frequently the site is spidered

  23. Four Laws of Crawling • A Crawler must show identification • A Crawler must obey the robots exclusion standard http://www.robotstxt.org/wc/norobots.html • A Crawler must not hog resources • A Crawler must report errors

  24. Lots of tricky aspects • Servers are often down or slow • Hyperlinks can get the crawler into cycles • Some websites have junk in the web pages • Now many pages have dynamic content • The web is HUGE

  25. The Internet Is Enormous Image from http://www.nature.com/nature/webmatters/tomog/tomfigs/fig1.html

  26. “Freshness” • Need to keep checking pages • Pages change • At different frequencies • Pages are removed • Many search engines cache the pages (store a copy on their own servers)

  27. What really gets crawled? • A small fraction of the Web that search engines know about; no search engine is exhaustive • Not the “live” Web, but the search engine’s index • Notthe “Deep Web” • Mostly HTML pages but other file types too: PDF, Word, PPT, etc.

  28. ii. Index (the database) Record information about each page • List of words • In the title? • How far down in the page? • Was the word in boldface? • URLs of pages pointing to this one • Anchor text on pages pointing to this one

  29. Inverted Index • How to store the words for fast lookup • Basic steps: • Make a “dictionary” of all the words in all of the web pages • For each word, list all the documents it occurs in. • Often omit very common words • “stop words” • Sometimes stem the words • (also called morphological analysis) • cats -> cat • running -> run

  30. Inverted Index Example Image from http://developer.apple.com /documentation/UserExperience/Conceptual/SearchKitConcepts/searchKit_basics/chapter_2_section_2.html

  31. Inverted Index • In reality, this index is HUGE • Need to store the contents across many machines • Need to do optimization tricks to make lookup fast.

  32. “travel” Load Balancer “travel” … … FE1 FE2 FE8 “travel” … … QI1 QI2 QI8 “travel” “travel” … Node1,1 Node1,2 Node1,3 Node1,N … Node2,1 Node2,2 Node2,3 Node2,N … Node3,1 Node3,2 Node3,3 Node3,N … Node4,1 Node4,2 Node4,3 Node4,N Query Serving Architecture • Index divided into segments each served by a node • Each row of nodes replicated for query load • Query integrator distributes query and merges results • Front end creates a HTML page with the query results

  33. iii. Results ranking • Search engine receives a query, then • Looks up the words in the index, retrieves many documents, then • Rank orders the pages and extracts “snippets” or summaries containing query words. • Most web search engines assume the user wants all of the words • These are complex and highly guarded algorithms unique to each search engine.

  34. Some ranking criteria • For a given candidate result page, use: • Number of matching query words in the page • Proximity of matching words to one another • Location of terms within the page • Location of terms within tags e.g. <title>, <h1>, link text, body text • Anchor text on pages pointing to this one • Frequency of terms on the page and in general • Link analysis of which pages point to this one • (Sometimes) Click-through analysis: how often the page is clicked on • How “fresh” is the page • Complex formulae combine these together.

  35. Measuring Importance of Linking • PageRank Algorithm • Idea: important pages are pointed to by other important pages • Method: • Each link from one page to another is counted as a “vote” for the destination page • But the importance of the starting page also influences the importance of the destination page. • And those pages scores, in turn, depend on those linking to them. Image and explanation from http://www.economist.com/science/tq/displayStory.cfm?story_id=3172188

  36. CRAFT SITES FOR FINDABILITY (SEO)

  37. Making Web Sites Attractive to Search Engines • Called “Search Engine Optimization” (SEO) • There is a LOT of information about this on the web • Most is about how to improve your site • Some is about “cheating”; avoid this • There are many tools to help you too.

  38. The Most Important Principle: Good, unique content trumps everything else.

  39. Content is Key • Web sites that are primarily high-quality, unique content will be ranked highly. • Not just links to other content • Not re-packaging of other content • Example: • My online book was top ranked for “search user interfaces” within one day of site launch. • It is also top ranked for many related queries.

  40. Web Site Characteristics • These can lead to high search engine ranking (but no guarantees): • High-quality, unique content. • Linked to by high-quality sites. • Been around a long time with consistent content.

  41. Keyword Placement • Search engines place “weight” on words according to where they are used • Place important words in • Title tags • Headings (H1 is key) and emphasized text • Visible body text • Description metadata – often used in search results snippets. • Alt text in images

  42. Keyword Variation • Describe the same concepts using different words within the relevant pages. • Compare “search interfaces” with “search user interfaces”in the next slide. • 1 hit versus 4 hits in the top 6 • I need to use more variation for the key concepts • But it must make sense in your page; • Don’t hide dictionaries of words ! • Can include them in the description metadata.

  43. put in aw-stat logs

  44. The Importance of URLs • Meaningful, short urls improve search engine ranking and usability • Urls that consist of computer-generated database queries can hurt rankings. • Urls with lots of redirects also hurt.

  45. The Importance of Titles • The title tag determines what words show up in the search results title. • Make them descriptive of the site • Vary them to differentiate them. • Example (next page) • Consistently varies the title to show how they differ. • But makes a mistake in the metadata description by putting the part that varies too far from the start, so it all looks the same.

  46. Robots Exclusion • It is important to check your robots.txt files to be sure they are allowing crawling. • If your server can’t handle a lot of traffic, use the site map file to slow crawlers down.

  47. Site Maps • There are two kinds of site maps: • A navigation structure visible to users • An XML file visible only to search engines • The latter is important to help ensure the pages on your site are crawled. • You can also specify the frequency with which you hope the pages will be crawled. • There are free tools to help you do this.

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