Software Engineering for Internet Applications - Student Community

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mentor (NULL if not assigned), date_of_request,date_of_assignment, mentee_goal. To support the query"who is the currently connected member mentoring" and build theworkspace subsection page for Jane you'll want to add an index onthe mentor column. To support the query "are there any mentors whoshould be notified about a message posted by a member" you wouldadd an index on the mentee column. If you were to make this aconcatenated index on mentee, mentor it would help the databaseidentify outstanding requests for mentors (mentor is NULL)efficiently for the "be a mentor page".Attempting to support the open/closed question status display andthe query "Which members have answered a lot of questions well?"might make you regret some of the data model decisions that youmade in the preceding exercises and/or in the Content Managementchapter exercises. In the Content Management chapter we have aheadline asking "What is Different about Discussion?" above thesuggestion that the content_raw table can be used to supportforum questions and answers. If you went down that route and wereimplementing the mentoring user experience this is where discussionwould diverge a bit from the rest of the content on the site. You needa way to represent in the database management system whether adiscussion forum question is open or closed. If you add adiscussion_forum_question_status column to thecontent_raw table you'll have a NULL column value whenever thecontent item is not a discussion forum question. That's not veryclean. You may also be adding a closed_question_p booleancolumn to indicate that a forum posting had been identified by theoriginal questioner as having answered the question. This will NULLfor more than 99 percent of content items. That's not a storageefficiency problem but it is sort of ugly.An alternative to adding columns is to build some sort of bag-on-thesidetable recording which questions are open and closed and whichanswers closed them. To decide whether or not this is a reasonableapproach it is worth starting by asking "In what percentage of querieswill the helper table need to be JOINed in?" When presenting articlesand comments you wouldn't need the table. When presenting thediscussion forum to a public user, i.e., someone who wasn't loggedin, the discussion forum page scripts wouldn't need the table data.You might only need these data when serving workspace pages tomembers and when serving an individual discussion forum thread toa logged-in member. It might be worth considering a table of thefollowing form:170host.Though neither request indicates a preferred media type, Google'sserver recognizes the "Blazer" browser that ships with Handspringpalm-top devices and redirects the browser, via the response linesHTTP/1.1 302 Found and Location:http://www.google.com/palm. Sadly, there is no centrallymaintained registry of user agents and therefore success with thismethod is largely a matter of programmer diligence.9.5 Exercise 3Summary. Paste the XHTML-MP example document above, startingwith the declaration and running through the closing tag, into a file called ex1.html on your Web server and loadthe example into different kinds of browsers. We recommend that youplace this file in a /mbl/ subdirectory underneath your Web server'spage root.Step 1 -- mobile browser. Load the page intoa mobile browser and admire your handiwork. Ifyou do not have access to a Web-enabledphone, install or locate emulator software,either a PC microbrowser emulator or Webbasedtool. See the links at the end of thischapter for suggestions. Suppose for a momentthat you had placed the document at/mbl/software-engineering-forinternetapplications/examples/example1.html.Would that affect the amount of time required tocomplete this exercise?Step 2 -- desktop browser. Now load the page into your favoritedesktop browser program. Marvel at the cross-browser compatibilityof your document. Compare your subjective experience of thecontent in the two cases, then answer the following question: In aworld where desktop browsers and mobile browsers can parse thesame markup syntax, do we need to distinguish between the two, orcan we serve the same document to every type of user?179
text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,video/xmng,image/png,image/jpeg,image/gif;q=0.2,*/*;q=0.1Note that Mozilla is making full use of the original conception of the Webin which the server and the client would negotiate to provide the userwith the best possible file in response to a request for an abstract URL.The order of the MIME types in the Accept header is irrelevant. Thebrowser indicates its preference with quality values, for example in thevalue text/html;q=0.9, Mozilla is indicating that plain vanillaHTML is less preferred than the three preceding XML types, whichdefault to a quality of 1.0. To learn more about this system, see thesection on "Quality Values" in the HTTP 1.1 specification, athttp://www.w3.org/Protocols/rfc2616/rfc2616.htmlA second method for distinguishing between desktop andmicrobrowsers is examining the User-Agent HTTP header.Consider the following two shell sessions, in which the user-typedinput is highlighted in bold:No Extra Headers% telnet www.google.com 80Trying 216.239.57.99...Connected to www.google.com.Escape character is '^]'.GET / HTTP/1.1HTTP/1.1 200 OKDate: Tue, 22 Apr 200301:20:53 GMTCache-control: privateContent-Type: text/htmlServer: GWS/2.0Content-length: 2691Google.........Connection closed by foreignhost.Claiming to be a Palm% telnet www.google.com 80Trying 216.239.57.99...Connected to www.google.com.Escape character is '^]'.GET / HTTP/1.1User-Agent: UPG1 UP/4.0(compatible; Blazer 1.0)HTTP/1.1 302 FoundDate: Tue, 22 Apr 200301:37:18 GMTLocation:http://www.google.com/palmContent-Type: text/htmlServer: GWS/2.0Content-length: 156302Moved302 MovedThe document has movedhere.Connection closed by foreign-- content_id is the primary key here; it is possible to-- have at most one row in this table for a row in the-- content_raw tablecreate table discussion_question_status (content_id not null primary keyreferences content_raw,status varchar(10)check (status in ('open', 'closed')),-- if the question is closed the next column will-- contain the content_id of the posting that closed itclosed_by references content_raw);-- make it fast to figure out whether a posting-- closed a questioncreate index discussion_question_status_by_closed_by ondiscussion_question_status(closed_by);As the community gains experience with this system it will probablyeventually want to give greater prominence to responses frommembers with a history of writing good answers. In a fully normalizeddata model the server would have to, for each answer displayed,count up the number of old answers from the author and query thediscussion_question_status table to figure out whatpercentage of those were marked as closing the question. In practiceyou'd probably want to maintain a denormalized metric as an extracolumn or columns in the users table, perhaps columns forn_answers_posted and n_answers_closing, counts maintainedby nightly batch updates or database triggers.Supporting the "initially show only to my mentor" option for newcontent would require the addition of a show_only_to_mentorcolumn to the content_raw table, where it could be used fordiscussion forum postings, comments on articles, and any othercontent item. Rather than changing all of the pages that use thecontent tables it would be easier to update the SQL views that thosetables use, e.g., articles_approved, so as to exclude contentthat should only be shown to a mentor.Some new page scripts would be required, at least the following:• /workspace -- a page or sidebar providing a logged-inmember with links to previously asked questions andpossibly other information as well, e.g., new content sincelast visit, recent content by members previously marked as178171
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SoftwareEngineering forInternetAppl
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Signature: ________________________
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end-users. We use every opportunity
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• availability of magnet content
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• we want to see if a student is
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you supply English-language queries
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What to do during lecturesWe try to
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The one-term cram courseWhen teachi
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332• spend a term learning how to
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Once we've taught students how to b
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has permission to perform each task
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UDDIUnixcustomer's credit card. If
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thousands of concurrent users. This
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OraclePerlnamed XYZ" without the pr
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LDAPLinuxbits per color, a vastly s
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FilterFirewallFlat-fileGIF318functi
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when there is an educational dimens
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system. The authors of the core pro
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Sign-OffsTry to schedule comprehens
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scheduling goals that both you and
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Client Tenure In Job (new, mid-term
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ReferencesEngagement ManagementSQL*
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Decision-makers often bring senior
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presentation to a panel of outsider
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300always been written by programme
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17.3 Professionalism in the Softwar
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Try to make sure that your audience
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Chapter 17WriteupIf I am not for my
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Suppose that an RDBMS failure were
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analysis programs analyzing standar
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at 9 hours 11 minutes 59 seconds pa
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found" will result in an access log
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15.18 Time and MotionThe team shoul
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select 227, 891, 'algorithm', curre
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create table km_object_views (objec
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• object-create• object-display
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The trees chapter of SQL for Web Ne
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);274-- ordering within a form, low
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and start the high-level document f
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Example Ontology 2: FlyingWe want a
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systems. What would a knowledge man
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spreadsheet". Other users can comme
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Chapter 15Metadata (and Automatic C
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{site url}{site description}en-usCo
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drawing on the intermodule API that
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At this point you have something of
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• description• URL for a photo
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Chapter 14Distributed Computing wit
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conduct programmer job interviews h
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Most admin pages can be excluded fr
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content that should distinguish one
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Chapter 13Planning ReduxA lot has c
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the Internet-specific problem of no
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wouldn't see these dirty tricks unl
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12.8 Exercise 4: Big BrotherGeneral
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than one call to contains in the sa
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way 1 1/16One might argue that this
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