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• What is the IPv6 equivalent to IPv4 RFC1918 addresses?

  - by Kumba

  Having a hard time wrapping my head around IPv6 here. A lot of the lingo seems targeted at enterprise-level IPv6 deployments, discussing link-local, site-local, global unicast, scopes, etc. Not a lot of solid information on really small networks, like home networks. I want to check my thinking and make sure I am getting the correct translations from IPv4-speak to IPv6-speak. The first question is, what's the equivalent of RFC1918 for IPv6? Initial searches suggested there was no equivalent. Then I stumbled upon Unique Local Addresses (RFC4193), and that states that all ULA's should be assigned the prefix fc00, followed by a 40-bit random number in the routing prefix. This random number is to "prevent collisions when two IPv6 networks are interconnected" -- again, another reference to an enterprise-level function. If I have a small local LAN at home, numbered using 192.168.4.0/24, what's my equivalent in IPv6's ULA scope? Assuming I will never, ever, tie that IPv6 address into the real internet (a router will NAT & firewall it), can I ignore the RFC to an extent and go with fc00::4:0/120? It also seems that any address in fc00::/7 are to be globally routable. Does this mean I'll need extra protections so my router would not automatically start advertising these private IPv6 addresses to the world? Second question, what's this link-local thing? Reading suggests a default-assigned address in the fe80::/10 range that has the last 64bits of the address comprised of the interface's MAC address. Seems to be required, too, but I'm annoyed by the constant discussion of it in relation to enterprise networks. Third question, what is scope id for? Seems to be yet another term tossed around in relation to enterprise networks, especially when interconnecting them, but almost no explanation on the smaller home network level. Can I see a scope ID AND CIDR notation used together? I.e., fc00::4:0/120%6, or are scope IDs only supposed to be applied to a single /128 IPv6 address?

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• suPHP not working

  - by amarc

  OS: Ubuntu 10.04 etc/suphp/suphp.conf: [global] ;Path to logfile logfile=/var/log/suphp/suphp.log ;Loglevel loglevel=info ;User Apache is running as webserver_user=www-data ;Path all scripts have to be in docroot=/home ;Path to chroot() to before executing script ;chroot=/mychroot ; Security options allow_file_group_writeable=false allow_file_others_writeable=false allow_directory_group_writeable=false allow_directory_others_writeable=false ;Check wheter script is within DOCUMENT_ROOT check_vhost_docroot=true ;Send minor error messages to browser errors_to_browser=false ;PATH environment variable env_path=/bin:/usr/bin ;Umask to set, specify in octal notation umask=0077 ; Minimum UID min_uid=100 ; Minimum GID min_gid=100 [handlers] ;Handler for php-scripts application/x-httpd-suphp="php:/usr/bin/php-cgi" ;Handler for CGI-scripts x-suphp-cgi="execute:!self" some vhost in sites-enabled: NameVirtualHost *:8080 <VirtualHost *:8080> ServerAdmin ... ServerName ... ServerAlias ... AddType application/x-httpd-php .php AddHandler application/x-httpd-php .php suPHP_Engine on suPHP_UserGroup user user suPHP_ConfigPath "/home/user/etc" suPHP_PHPPath /usr/bin DocumentRoot /home/user/web/site.com/ ErrorLog /var/log/apache2/site.com-error_log CustomLog /var/log/apache2/site.com-access_log common <Directory /home/user/web/site.com/> Order Deny,Allow Allow from all Options +Indexes </Directory> </VirtualHost> But when I did nano /home/user/web/id.php and paste <?php system('id'); ?> in it, result I get is: uid=33(www-data) gid=33(www-data) groups=33(www-data) Have no idea what to do so I was hoping comunity could help ty.

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• locale: What is the LANGUAGE variable used for? (and when?)

  - by seya

  I am trying to understand the locales used in Linux. On my Ubuntu 11.10 system locale puts out the following: LANG=en_DK.UTF-8 LANGUAGE=en_GB:en LC_CTYPE=en_GB.UTF-8 LC_NUMERIC="en_DK.UTF-8" LC_TIME="en_DK.UTF-8" LC_COLLATE=en_GB.UTF-8 LC_MONETARY="en_DK.UTF-8" LC_MESSAGES=en_GB.UTF-8 LC_PAPER="en_DK.UTF-8" LC_NAME="en_DK.UTF-8" LC_ADDRESS="en_DK.UTF-8" LC_TELEPHONE="en_DK.UTF-8" LC_MEASUREMENT="en_DK.UTF-8" LC_IDENTIFICATION="en_DK.UTF-8" LC_ALL= (en_dk is for using international day format, continental European number formatting (1.234,56) etc.) I think I understand what the LC_* family does, that LANG is the fallback if one of them is not set and that LC_ALL sets all of the LC_* variables to its value. What I don't know yet, is what LANGUAGE is used for. The notation en_GB:en reminds me of the Accept-Language HTTP header. With the settings above it would mean, British English is used, if a translation for it exists. Otherwise any existing English translation (en_US, en_AU, ..., whatever) would be used. Am I right so far? Also what programs actually obey the LANGUAGE setting? In how far is it different from LC_MESSAGES? Unfortunately, man locale only documents the LC_* family. And searching the web for 'linux locale LANGUAGE' or similar is a mute point. (Of course language is a word often used when talking about locales, and it may also be shown just in the output of locale without being discussed). Does anybody of you can help me out there?

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• How to reproject a shapefile from WGS 84 to Spherical/Web Mercator projection.

  - by samkea

  Definitions: You will need to know the meaning of these terms below. I have given a small description to the acronyms but you can google and know more about them. #1:WGS-84- World Geodetic Systems (1984)- is a standard reference coordinate system used for Cartography, Geodesy and Navigation. #2: EPGS-European Petroleum Survey Group-was a scientific organization with ties to the European petroleum industry consisting of specialists working in applied geodesy, surveying, and cartography related to oil exploration. EPSG::4326 is a common coordinate reference system that refers to WGS84 as (latitude, longitude) pair coordinates in degrees with Greenwich as the central meridian. Any degree representation (e.g., decimal or DMSH: degrees minutes seconds hemisphere) may be used. Which degree representation is used must be declared for the user by the supplier of data. So, the Spherical/Web Mercator projection is referred to as EPGS::3785 which is renamed to EPSG:900913 by google for use in googlemaps. The associated CRS(Coordinate Reference System) for this is the "Popular Visualisation CRS / Mercator ". This is the kind of projection that is used by GoogleMaps, BingMaps,OSM,Virtual Earth, Deep Earth excetra...to show interactive maps over the web with thier nearly precise coordinates.  Reprojection: After reading alot about reprojecting my coordinates from the deepearth project on Codeplex, i still could not do it. After some help from a colleague, i got my ball rolling.This is how i did it. #1 You need to download and open your shapefile using Q-GIS; its the one with the biggest number of coordinate reference systems/ projections. #2 Use the plugins menu, and enable ftools and the WFS plugin. #3 Use the Vector menu--> Data Management Tools and choose define current projection. Enable, use predefined reference system and choose WGS 84 coodinate system. I am personally in zone 36, so i chose WGS84-UTM Zone 36N under ( Projected Coordinate Systems--> Universal Transverse Mercator) and click ok. #4 Now use the Vector menu--> Data Management Tools and choose export to new projection. The same dialog will pop-up. Now choose WGS 84 EPGS::4326 under Geodetic Coordinate Systems. My Input user Defined Spatial Reference System should looks like this: +proj=tmerc +lat_0=0 +lon_0=33 +k=0.9996 +x_0=500000 +y_0=200000 +ellps=WGS84 +datum=WGS84 +units=m +no_defs Your Output user Defined Spatial Reference System should look like this: +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs Browse for the place where the shapefile is going to be and give the shapefile a name(like origna_reprojected). If it prompts you to add the projected layer to the TOC, accept. There, you have your re-projected map with latitude and longitude pair of coordinates. #5 Now, this is not the actual Spherical/Web Mercator projection, but dont worry, this is where you have to stop. All the other custom web-mapping portals will pick this projection and transform it into EPGS::3785 or EPSG:900913 but the coordinates will still remain as the LatLon pair of the projected shapefile. If you want to test, a particular know point, Q-GIS has a lot of room for that. Go ahead and test it.

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• From NaN to Infinity...and Beyond!

  - by Tony Davis

  It is hard to believe that it was once possible to corrupt a SQL Server Database by storing perfectly normal data values into a table; but it is true. In SQL Server 2000 and before, one could inadvertently load invalid data values into certain data types via RPC calls or bulk insert methods rather than DML. In the particular case of the FLOAT data type, this meant that common 'special values' for this type, namely NaN (not-a-number) and +/- infinity, could be quite happily plugged into the database from an application and stored as 'out-of-range' values. This was like a time-bomb. When one then tried to query this data; the values were unsupported and so data pages containing them were flagged as being corrupt. Any query that needed to read a column containing the special value could fail or return unpredictable results. Microsoft even had to issue a hotfix to deal with failures in the automatic recovery process, caused by the presence of these NaN values, which rendered the whole database inaccessible! This problem is history for those of us on more current versions of SQL Server, but its ghost still haunts us. Recently, for example, a developer on Red Gate’s SQL Response team reported a strange problem when attempting to load historical monitoring data into a SQL Server 2005 database via the C# ADO.NET provider. The ratios used in some of their reporting calculations occasionally threw out NaN or infinity values, and the subsequent attempts to load these values resulted in a nasty error. It turns out to be a different manifestation of the same problem. SQL Server 2005 still does not fully support the IEEE 754 standard for floating point numbers, in that the FLOAT data type still cannot handle NaN or infinity values. Instead, they just added validation checks that prevent the 'invalid' values from being loaded in the first place. For people migrating from SQL Server 2000 databases that contained out-of-range FLOAT (or DATETIME etc.) data, to SQL Server 2005, Microsoft have added to the latter's version of the DBCC CHECKDB (or CHECKTABLE) command a DATA_PURITY clause. When enabled, this will seek out the corrupt data, but won’t fix it. You have to do this yourself in what can often be a slow, painful manual process. Our development team, after a quizzical shrug of the shoulders, simply decided to represent NaN and infinity values as NULL, and move on, accepting the minor inconvenience of not being able to tell them apart. However, what of scientific, engineering and other applications that really would like the luxury of being able to both store and access these perfectly-reasonable floating point data values? The sticking point seems to be the stipulation in the IEEE 754 standard that, when NaN is compared to any other value including itself, the answer is "unequal" (i.e. FALSE). This is clearly different from normal number comparisons and has repercussions for such things as indexing operations. Even so, this hardly applies to infinity values, which are single definite values. In fact, there is some encouraging talk in the Connect note on this issue that they might be supported 'in the SQL Server 2008 timeframe'. If didn't happen; SQL 2008 doesn't support NaN or infinity values, though one could be forgiven for thinking otherwise, based on the MSDN documentation for the FLOAT type, which states that "The behavior of float and real follows the IEEE 754 specification on approximate numeric data types". However, the truth is revealed in the XPath documentation, which states that "…float (53) is not exactly IEEE 754. For example, neither NaN (Not-a-Number) nor infinity is used…". Is it really so hard to fix this problem the right way, and properly support in SQL Server the IEEE 754 standard for the floating point data type, NaNs, infinities and all? Oracle seems to have managed it quite nicely with its BINARY_FLOAT and BINARY_DOUBLE types, so it is technically possible. We have an enterprise-class database that is marketed as being part of an 'integrated' Windows platform. Absurdly, we have .NET and XPath libraries that fully support the standard for floating point numbers, and we can't even properly store these values, let alone query them, in the SQL Server database! Cheers, Tony.

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• InSync12 and Australia Visits: UX is Global, Regional, Everywhere!

  - by ultan o'broin

  I attended the Australian Oracle User Group (AUSOUG) and Quest International User Group's InSync12 event in Melbourne, Australia: the user group conference for Oracle products in the ANZ region. I demoed Oracle Fusion Applications and then presented how Oracle crafted the world class Fusion Apps user experience (UX). I explained about the Oracle user experience design pattern strategy of uptake for all apps, not just Fusion, and what our UX pattern externalization strategy means for customers, partners, and ADF developers. A great conference, lots of energy, the InSync12 highlights for me were Oracle's Senior Vice President Cliff Godwin’s fast-moving Oracle E-Business Suite (EBS) roadshow with the killer Oracle Endeca user experience uptake, and Oracle ADF product outreachmeister Chris Muir’s (@chriscmuir) session on Oracle ADF Mobile solution and his hands-on mobile app development showing how existing ADF/JDev skills can build a secure, code once-deploy-to-many-device hybrid app solution in minutes. Cliff Godwin shows off the Oracle Endeca integration with Oracle E-Business Suite. Chris Muir talked the talk and then walked the walked with Oracle ADF Mobile. Applications UX was mixing it up with the crowd at InSync12 too, showing off cool mobile UX solutions, gathering data for future innovations, and engaging with EBS, JD Edwards, and PeopleSoft apps customers and partners. User conferences such as InSync12 are an important part of our Oracle Applications UX user-centered design process, giving real apps users the opportunity to make real inputs and a way for us to watch and to listen to their needs and wants and get views on current and emerging UX too. Eric Stilan (@icondaddy) of Applications UX uses an iPad to gather feedback on the latest UX designs from conference attendees. While in Melbourne, I also visited impressive Oracle partner, Callista for a major ADF and UX pow-wow, and was the er, star of a very proactive event hosted by another partner Park Lane Information Technology (coordinated by Bambi Price (@bambiprice) of ODTUG) where I explained what UX is about, and how partner and customers can engage, participate and deploy that Applications UX scientific insight to advantage for their entire business. I also paired up with Oracle Australia in Sydney to visit key customers while there, and back at Oracle in Melbourne I spoke with sales consultants and account managers about regional opportunities and UX strategy, and came away with an understanding of what makes the Oracle market tick in Australia. Mobile worker solution development and user experience is hot news in Australia, and this was a great opportunity to team up with Chris Muir and show how the alignment of the twin stars of UX design patterns and ADF technology enables developers to make great-looking, usable apps that really sparkle. Our UX design patterns--or functional (UI) patterns, to use the developer world language--means that developers now have not only a great tool set to build apps on Oracle ADF/FMW but proven, tested usability solutions to solve common problems they can apply in the IDE too. In all, a whirlwind UX visit, packed with events and delivery opportunities, and all too short a time in the wonderful city of Melbourne. I need to get back there soon! For those who need a reminder, there's a website explaining how to get involved with, and participate in, Applications User Experience (including the Oracle Usability Advisory Board) events and programs. Thank you to AUSOUG, Quest, InSync, Callista, Park Lane IT, everyone at Oracle Australia, Chris Muir, and all the other people who came together to make this a productive visit. Stay tuned for more UX developments and engagements in the region on the Oracle VoX blog and Usable Apps website too!

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• What packages do I need to compile .tex documents using XeLaTeX?

  - by maria

  Hi I'm aware of the existence of similar threads on this forum. But any of replies mach to my problem. I'm using Ubuntu 10.4 and I hadn't problems with fonts till I've decided to use XeLaTeX instead of LaTeX (cf http://tex.stackexchange.com/questions/12347/typesetting-a-document-using-arabic-script/12358#12358). The problem is that I'm not able to compile any .tex document using XeLaTeX, as well as properly display XeLaTeX documentation. As I've learn thanks to mentioned thread, XeLaTeX uses the fonts availables in general in the system. I was trying yo read fontspec documentation, but it opens in pdf with a lot of white gaps and terminal output (quite long) consist mostly of errors. This are just few lines of it: Error: Missing language pack for 'Adobe-Japan1' mapping Error: Unknown font tag 'F5.1' Error (24124): No font in show Error: Unknown font tag 'F5.1' I was trying to compile simple XeLaTeX file: \documentclass{article} \usepackage{fontspec} \setmainfont{Linux Libertine O} \begin{document} Hello World! \end{document} without succes. This is terminal output of compilation: This is XeTeX, Version 3.1415926-2.2-0.9995.2 (TeX Live 2009/Debian) restricted \write18 enabled. entering extended mode (./ex.tex LaTeX2e <2009/09/24> Babel <v3.8l> and hyphenation patterns for english, usenglishmax, dumylang, noh yphenation, polish, loaded. (/usr/share/texmf-texlive/tex/latex/base/article.cls Document Class: article 2007/10/19 v1.4h Standard LaTeX document class (/usr/share/texmf-texlive/tex/latex/base/size10.clo)) (/usr/share/texmf-texlive/tex/xelatex/fontspec/fontspec.sty (/usr/share/texmf-texlive/tex/generic/ifxetex/ifxetex.sty) (/usr/share/texmf-texlive/tex/latex/tools/calc.sty) (/usr/share/texmf-texlive/tex/latex/xkeyval/xkeyval.sty (/usr/share/texmf-texlive/tex/generic/xkeyval/xkeyval.tex (/usr/share/texmf-texlive/tex/generic/xkeyval/keyval.tex))) (/usr/share/texmf-texlive/tex/latex/base/fontenc.sty (/usr/share/texmf-texlive/tex/xelatex/euenc/eu1enc.def) (/usr/share/texmf-texlive/tex/xelatex/euenc/eu1lmr.fd)) fontspec.cfg loaded. (/usr/share/texmf-texlive/tex/xelatex/fontspec/fontspec.cfg))kpathsea: Invalid fontname `Linux Libertine O', contains ' ' ! Font \zf@basefont="Linux Libertine O" at 10.0pt not loadable: Metric (TFM) fi le or installed font not found. \zf@fontspec ...ntname \zf@suffix " at \f@size pt \unless \ifzf@icu \zf@set@... l.3 \setmainfont{Linux Libertine O} ? I can't find Linux Libertine O. Searching for otf- by aptitude gives as result: maria@maria-laptop:/etc/fonts$ aptitude search otf p emdebian-rootfs - emdebian root filesystem support p libotf-bin - A Library for handling OpenType Font - utilities p libotf-dev - A Library for handling OpenType Font - development i libotf0 - A Library for handling OpenType Font - runtime p libotf0-dbg - The libotf libraries and debugging symbols p libpam-dotfile - A PAM module which allows users to have more than one password p livecd-rootfs - construction script for the livecd rootfs p makebootfat - Utility to create a bootable FAT filesystem p otf-ipaexfont - Japanese OpenType font, IPAexFont (IPAexGothic/Mincho) p otf-ipaexfont-gothic - Japanese OpenType font, IPAexFont (IPAexGothic) p otf-ipaexfont-mincho - Japanese OpenType font, IPAexFont (IPAexMincho) p otf-ipafont - Japanese OpenType font set, IPAfont p otf-ipafont-gothic - Japanese OpenType font set, IPA Gothic font p otf-ipafont-mincho - Japanese OpenType font set, IPA Mincho font p otf-stix - the Scientific and Technical Information eXchange fonts p otf-thai-tlwg - Thai fonts in OpenType format p otf-yozvox-yozfont - Japanese proportional Handwriting OpenType font p otf2bdf - generate BDF bitmap fonts from OpenType outline fonts p robotfindskitten - Zen Simulation of robot finding kitten So font in question is not just uninstalled, but not available, if I'm not wrong. Does it mean that I lack some repositoires? I was trying also to apply solution from the thread How do I reinstall default fonts?, but the result is: maria@maria-laptop:~$ sudo apt-get install msttcorefonts [sudo] password for maria: Reading package lists... Done Building dependency tree Reading state information... Done Note, selecting ttf-mscorefonts-installer instead of msttcorefonts ttf-mscorefonts-installer is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. maria@maria-laptop:~$ It seems that is not a usual problem for use of XeLaTeX; nobody in the mentioned thread suggested instalation of anything else than TeX Live. Thanks in advance

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• SQL SERVER – Introduction to Big Data – Guest Post

  - by pinaldave

  BIG Data – such a big word – everybody talks about this now a days. It is the word in the database world. In one of the conversation I asked my friend Jasjeet Sigh the same question – what is Big Data? He instantly came up with a very effective write-up.  Jasjeet is working as a Technical Manager with Koenig Solutions. He leads the SQL domain, and holds rich IT industry experience. Talking about Koenig, it is a 19 year old IT training company that offers several certification choices. Some of its courses include SharePoint Training, Project Management certifications, Microsoft Trainings, Business Intelligence programs, Web Design and Development courses etc. Big Data, as the name suggests, is about data that is BIG in nature. The data is BIG in terms of size, and it is difficult to manage such enormous data with relational database management systems that are quite popular these days. Big Data is not just about being large in size, it is also about the variety of the data that differs in form or type. Some examples of Big Data are given below : Scientific data related to weather and atmosphere, Genetics etc Data collected by various medical procedures, such as Radiology, CT scan, MRI etc Data related to Global Positioning System Pictures and Videos Radio Frequency Data Data that may vary very rapidly like stock exchange information Apart from difficulties in managing and storing such data, it is difficult to query, analyze and visualize it. The characteristics of Big Data can be defined by four Vs: Volume: It simply means a large volume of data that may span Petabyte, Exabyte and so on. However it also depends organization to organization that what volume of data they consider as Big Data. Variety: As discussed above, Big Data is not limited to relational information or structured Data. It can also include unstructured data like pictures, videos, text, audio etc. Velocity:  Velocity means the speed by which data changes. The higher is the velocity, the more efficient should be the system to capture and analyze the data. Missing any important point may lead to wrong analysis or may even result in loss. Veracity: It has been recently added as the fourth V, and generally means truthfulness or adherence to the truth. In terms of Big Data, it is more of a challenge than a characteristic. It is difficult to ascertain the truth out of the enormous amount of data and the one that has high velocity. There are always chances of having un-precise and uncertain data. It is a challenging task to clean such data before it is analyzed. Big Data can be considered as the next big thing in the IT sector in terms of innovation and development. If appropriate technologies are developed to analyze and use the information, it can be the driving force for almost all industrial segments. These include Retail, Manufacturing, Service, Finance, Healthcare etc. This will help them to automate business decisions, increase productivity, and innovate and develop new products. Thanks Jasjeet Singh for an excellent write up.  Jasjeet Sign is working as a Technical Manager with Koenig Solutions. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Database, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Big Data

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• what differs a computer scientist/software engineer to regular people who learn programming language and APIs?

  - by Amumu

  In University, we learn and reinvent the wheel a lot to truly learn the programming concepts. For example, we may learn assembly language to understand, what happens inside the box, and how the system operates, when we execute our code. This helps understanding higher level concepts deeper. For example, memory management like in C is just an abstraction of manually managed memory contents and addresses. The problem is, when we're going to work, usually productivity is required more. I could program my own containers, or string class, or date/time (using POSIX with C system call) to do the job, but then, it would take much longer time to use existing STL or Boost library, which abstract all of those thing and very easy to use. This leads to an issue, that a regular person doesn't need to get through all the low level/under the hood stuffs, who learns only one programming language and using language-related APIs. These people may eventually compete with the mainstream graduates from computer science or software engineer and call themselves programmers. At first, I don't think it's valid to call them programmers. I used to think, a real programmer needs to understand the computer deeply (but not at the electronic level). But then I changed my mind. After all, they get the job done and satisfy all the test criteria (logic, performance, security...), and in business environment, who cares if you're an expert and understand how computer works or not. You may get behind the "amateurs" if you spend to much time learning about how things work inside. It is totally valid for those people to call themselves programmers. This makes me confuse. So, after all, programming should be considered an universal skill? Does programming language and concepts matter or the problems we solve matter? For example, many C/C++ vs Java and other high level language, one of the main reason is because C/C++ features performance, as well as accessing low level facility. One of the main reason (in my opinion), is coding in C/C++ seems complex, so people feel good about it (not trolling anyone, just my observation, and my experience as well. Try to google "C hacker syndrome"). While Java on the other hand, made for simplifying programming tasks to help developers concentrate on solving their problems. Based on Java rationale, if the programing language keeps evolve, one day everyone can map their logic directly with natural language. Everyone can program. On that day, maybe real programmers are mathematicians, who could perform most complex logic (including business logic and academic logic) without worrying about installing/configuring compiler, IDEs? What's our job as a computer scientist/software engineer? To solve computer specific problems or to solve problems in general? For example, take a look at this exame: http://cm.baylor.edu/ICPCWiki/attach/Problem%20Resources/2010WorldFinalProblemSet.pdf . The example requires only basic knowledge about the programming language, but focus more on problem solving with the language. In sum, what differs a computer scientist/software engineer to regular people who learn programming language and APIs? A mathematician can be considered a programmer, if he is good enough to use programming language to implement his formula. Can we programmer do this? Probably not for most of us, since we specialize about computer, not math. An electronic engineer, who learns how to use C to program for his devices, can be considered a programmer. If the programming languages keep being simplified, may one day the software engineers, who implements business logic and create softwares, be obsolete? (Not for computer scientist though, since many of the CS topics are scientific, and science won't change, but technology will).

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• Crime Scene Investigation: SQL Server

  - by Rodney Landrum

  “The packages are running slower in Prod than they are in Dev” My week began with this simple declaration from one of our lead BI developers, quickly followed by an emailed spreadsheet demonstrating that, over 5 executions, an extensive ETL process was running average 630 seconds faster on Dev than on Prod. The situation needed some scientific investigation to determine why the same code, the same data, the same schema would yield consistently slower results on a more powerful server. Prod had yet to be officially christened with a “Go Live” date so I had the time, and having recently been binge watching CSI: New York, I also had the inclination. An inspection of the two systems, Prod and Dev, revealed the first surprise: although Prod was indeed a “bigger” system, with double the amount of RAM of Dev, the latter actually had twice as many processor cores. On neither system did I see much sign of resources being heavily taxed, while the ETL process was running. Without any real supporting evidence, I jumped to a conclusion that my years of performance tuning should have helped me avoid, and that was that the hardware differences explained the better performance on Dev. We spent time setting up a Test system, similarly scoped to Prod except with 4 times the cores, and ported everything across. The results of our careful benchmarks left us truly bemused; the ETL process on the new server was slower than on both other systems. We burned more time tweaking server configurations, monitoring IO and network latency, several times believing we’d uncovered the smoking gun, until the results of subsequent test runs pitched us back into confusion. Finally, I decided, enough was enough. Hadn’t I learned very early in my DBA career that almost all bottlenecks were caused by code and database design, not hardware? It was time to get back to basics. With over 100 SSIS packages and hundreds of queries, each handling specific tasks such as file loads, bulk inserts, transforms, logging, and so on, the task seemed formidable. And yet, after barely an hour spent with Profiler, Extended Events, and wait statistics DMVs, I had a lead in the shape of a query that joined three tables, containing millions of rows, returned 3279 results, but performed 239K logical reads. As soon as I looked at the execution plans for the query in Dev and Test I saw the culprit, an implicit conversion warning on a join predicate field that was numeric in one table and a varchar(50) in another! I turned this information over to the BI developers who quickly resolved the data type mismatches and found and fixed “several” others as well. After the schema changes the same query with the same databases ran in under 1 second on all systems and reduced the logical reads down to fewer than 300. The analysis also revealed that on Dev, the ETL task was pulling data across a LAN, whereas Prod and Test were connected across slower WAN, in large part explaining why the same process ran slower on the latter two systems. Loading the data locally on Prod delivered a further 20% gain in performance. As we progress through our DBA careers we learn valuable lessons. Sometimes, with a project deadline looming and pressure mounting, we choose to forget them. I was close to giving into the temptation to throw more hardware at the problem. I’m pleased at least that I resisted, though I still kick myself for not looking at the code on day one. It can seem a daunting prospect to return to the fundamentals of the code so close to roll out, but with the right tools, and surprisingly little time, you can collect the evidence that reveals the true problem. It is a lesson I trust I will remember for my next 20 years as a DBA, if I’m ever again tempted to bypass the evidence.

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• I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

  - by Register Sole

  Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to be able to stack. I also want friction and gravity. I have a detection mechanism that returns the separating axis, how long the polygons are overlapping, and up to 2 points of contact. For the response, I am currently using an impulse-based response, which main idea is: find the separating axis, length of overlap, and the point of contact (if there are two, pick a random point between to simulate averaged force. i believe there are better ways than this) separate the object (modifying their positions, taking into account of their masses. i do not separate them completely though, to keep track that they are colliding to reduce jitter) calculate normal force based on the coefficient of restitution as if there is no friction. calculate friction, as if there is no normal force. I also assume that the direction of the friction is the same throughout the collision. apply the two forces (which result in a rather inaccurate result, since each force is calculated as if the other is not present. for non-rotating bodies though, this method is exact) I am aware that this method requires the coefficient of friction to be sufficiently small due to the assumption that the direction of friction stays the same in a collision. Also, the result is visually satisfying if gravity is not present. However, when there is gravity, objects on ground jitter and drift (even with zero coefficient of restitution)! It also happens for stacking objects. Larger coefficient of restitution and gravity increase the jittering. I hope you can help me with this. Some things i would like to know more about is how to handle collision with two point of contacts (how to end up having an object sitting still on the ground?), how to reduce, and prevent if possible, jitter and drift (do people use the most accurate method possible, or is there a trick to overcome this?), and how to handle multiple objects collision (for example, in the case of stacking objects, how do I check collisions between all of them and keep them all stable at every frame so they don't jitter?). A total reformulation of my algorithm is also welcomed, as long as it works. Another thing to note is that I am not making a Physics game, so I only need a visually satisfying response (though a realistic response is preferable, if it is not performance-heavy). But surely jittering and drifting objects on flat ground are not at all acceptable. In addition, I am a Physics student, so feel free to talk about impulse and whatever needed. Finally, I'm sorry for the long post. I tried to be as concise as I can. Thank you for reading it! EDIT It seems what I didn't manage to come up all this time is to separate resting contact as a class of its own and how to solve them. Currently reading the paper suggested by Jedediah. More suggestions on the topic are welcome :) CASE CLOSED After reading various papers referenced in the paper, successfully implemented simultaneous impulse method (referring to the original paper by Erin Catto, [Catt05]). Thanks maaaan!! The paper is wonderful. The current system is visibly much better than the previous. Still haven't separated resting contact as a class of its own though, which brings me to my next question. Love you all! Haha (sorry, I'm just so happy thanks to you).

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• General Web Programming/designing Question: ?

  - by Prasad

  hi, I have been in web programming for 2 years (Self taught - a biology researcher by profession). I designed a small wiki with needed functionalities and a scientific RTE - ofcourse lot is expected. I used mootools framework and AJAX extensively. I was always curious when ever I saw the query strings passed from URL. Long encrypted query string directly getting passed to the server. Especially Google's design is such. I think this is the start of providing a Web Service to a client - I guess. Now, my question is : is this a special, highly professional, efficient / advanced web design technique to communicate queries via the URL ? I always felt that direct URL based communication is faster. I tried my bit and could send a query through the URL directly. here is the link: http://sgwiki.sdsc.edu/getSGMPage.php?8 By this , the client can directly link to the desired page instead of searching and / or can automate. There are many possibilities. The next request: Can I be pointed to such technique of web programming? oops: I am sorry, If I have not been able to convey my request clearly. Prasad.

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• Are there any decent free JAVA data plotting libraries out there?

  - by Kurt W. Leucht

  On a recent JAVA project, we needed a free JAVA based real-time data plotting utility. After much searching, we found this tool called the Scientific Graphics Toolkit or SGT from NOAA. It seemed pretty robust, but we found out that it wasn't terribly configurable. Or at least not configurable enough to meet our needs. We ended up digging very deeply into the JAVA code and reverse engineering the code and changing it all around to make the plot tool look and act the way we wanted it to look and act. Of course, this killed any chance for future upgrades from NOAA. So what free or cheap JAVA based data plotting tools or libraries do you use? Followup: Thanks for the JFreeChart suggestions. I checked out their website and it looks like a very nice data charting and plotting utility. I should have made it clear in my original question that I was looking specifically to plot real-time data. I corrected my question above to make that point clear. It appears that JFreeChart support for live data is marginal at best, though. Any other suggestions out there?

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• Compression algorithm for IEEE-754 data

  - by David Taylor

  Anyone have a recommendation on a good compression algorithm that works well with double precision floating point values? We have found that the binary representation of floating point values results in very poor compression rates with common compression programs (e.g. Zip, RAR, 7-Zip etc). The data we need to compress is a one dimensional array of 8-byte values sorted in monotonically increasing order. The values represent temperatures in Kelvin with a span typically under of 100 degrees. The number of values ranges from a few hundred to at most 64K. Clarifications All values in the array are distinct, though repetition does exist at the byte level due to the way floating point values are represented. A lossless algorithm is desired since this is scientific data. Conversion to a fixed point representation with sufficient precision (~5 decimals) might be acceptable provided there is a significant improvement in storage efficiency. Update Found an interesting article on this subject. Not sure how applicable the approach is to my requirements. http://users.ices.utexas.edu/~burtscher/papers/dcc06.pdf

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• What is the most platform- and Python-version-independent way to make a fast loop for use in Python?

  - by Statto

  I'm writing a scientific application in Python with a very processor-intensive loop at its core. I would like to optimise this as far as possible, at minimum inconvenience to end users, who will probably use it as an uncompiled collection of Python scripts, and will be using Windows, Mac, and (mainly Ubuntu) Linux. It is currently written in Python with a dash of NumPy, and I've included the code below. Is there a solution which would be reasonably fast which would not require compilation? This would seem to be the easiest way to maintain platform-independence. If using something like Pyrex, which does require compilation, is there an easy way to bundle many modules and have Python choose between them depending on detected OS and Python version? Is there an easy way to build the collection of modules without needing access to every system with every version of Python? Does one method lend itself particularly to multi-processor optimisation? (If you're interested, the loop is to calculate the magnetic field at a given point inside a crystal by adding together the contributions of a large number of nearby magnetic ions, treated as tiny bar magnets. Basically, a massive sum of these.) # calculate_dipole # ------------------------- # calculate_dipole works out the dipole field at a given point within the crystal unit cell # --- # INPUT # mu = position at which to calculate the dipole field # r_i = array of atomic positions # mom_i = corresponding array of magnetic moments # --- # OUTPUT # B = the B-field at this point def calculate_dipole(mu, r_i, mom_i): relative = mu - r_i r_unit = unit_vectors(relative) #4pi / mu0 (at the front of the dipole eqn) A = 1e-7 #initalise dipole field B = zeros(3,float) for i in range(len(relative)): #work out the dipole field and add it to the estimate so far B += A*(3*dot(mom_i[i],r_unit[i])*r_unit[i] - mom_i[i]) / sqrt(dot(relative[i],relative[i]))**3 return B

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• How are you taking advantage of Multicore?

  - by tgamblin

  As someone in the world of HPC who came from the world of enterprise web development, I'm always curious to see how developers back in the "real world" are taking advantage of parallel computing. This is much more relevant now that all chips are going multicore, and it'll be even more relevant when there are thousands of cores on a chip instead of just a few. My questions are: How does this affect your software roadmap? I'm particularly interested in real stories about how multicore is affecting different software domains, so specify what kind of development you do in your answer (e.g. server side, client-side apps, scientific computing, etc). What are you doing with your existing code to take advantage of multicore machines, and what challenges have you faced? Are you using OpenMP, Erlang, Haskell, CUDA, TBB, UPC or something else? What do you plan to do as concurrency levels continue to increase, and how will you deal with hundreds or thousands of cores? If your domain doesn't easily benefit from parallel computation, then explaining why is interesting, too. Finally, I've framed this as a multicore question, but feel free to talk about other types of parallel computing. If you're porting part of your app to use MapReduce, or if MPI on large clusters is the paradigm for you, then definitely mention that, too. Update: If you do answer #5, mention whether you think things will change if there get to be more cores (100, 1000, etc) than you can feed with available memory bandwidth (seeing as how bandwidth is getting smaller and smaller per core). Can you still use the remaining cores for your application?

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• Bibliography behaves strange in lyx.

  - by Orjanp

  Hi! I have created a Bibliography section in my document written in lyx. It uses a book layout. For some reason it did start over again when I added some more entries. The new entries was made some time later than the first ones. I just went down to key-27 and hit enter. Then it started on key-1 again. Does anyone know why it behaves like this? The lyx code is below. \begin{thebibliography}{34} \bibitem{key-6}Lego mindstorms, http://mindstorms.lego.com/en-us/default.aspx \bibitem{key-7}C.A.R. Hoare. Communicating sequential processes. Communications of the ACM, 21(8):666-677, pages 666\textendash{}677, August 1978. \bibitem{key-8}C.A.R. Hoare. Communicating sequential processes. Prentice-Hall, 1985. \bibitem{key-9}CSPBuilder, http://code.google.com/p/cspbuilder/ \bibitem{key-10}Rune Møllegård Friborg and Brian Vinter. CSPBuilder - CSP baset Scientific Workflow Modelling, 2008. \bibitem{key-11}Labview, http://www.ni.com/labview \bibitem{key-12}Robolab, http://www.lego.com/eng/education/mindstorms/home.asp?pagename=robolab \bibitem{key-13}http://code.google.com/p/pycsp/ \bibitem{key-14}Paparazzi, http://paparazzi.enac.fr \bibitem{key-15}Debian, http://www.debian.org \bibitem{key-16}Ubuntu, http://www.ubuntu.com \bibitem{key-17}GNU, http://www.gnu.org \bibitem{key-18}IVY, http://www2.tls.cena.fr/products/ivy/ \bibitem{key-19}Tkinter, http://wiki.python.org/moin/TkInter \bibitem{key-20}pyGKT, http://www.pygtk.org/ \bibitem{key-21}pyQT4, http://wiki.python.org/moin/PyQt4 \bibitem{key-22}wxWidgets, http://www.wxwidgets.org/ \bibitem{key-23}wxPython GUI toolkit, http://www.wxPython.org \bibitem{key-24}Python programming language, http://www.python.org \bibitem{key-25}wxGlade, http://wxglade.sourceforge.net/ \bibitem{key-26}http://numpy.scipy.org/ \bibitem{key-27}http://www.w3.org/XML/ \bibitem{key-1}IVY software bus, http://www2.tls.cena.fr/products/ivy/ \bibitem{key-2}sdas \bibitem{key-3}sad \bibitem{key-4}sad \bibitem{key-5}fsa \bibitem{key-6}sad \bibitem{key-7} \end{thebibliography}

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• Tips on managing dependencies for a release?

  - by Andrew Murray

  Our system comprises many .NET websites, class libraries, and a MSSQL database. We use SVN for source control and TeamCity to automatically build to a Test server. Our team is normally working on 4 or 5 projects at a time. We try to lump many changes into a largish rollout every 2-4 weeks. My problem is with keeping track of all the dependencies for a rollout. Example: Website A cannot go live until we've rolled out Branch X of Class library B, built in turn against the Trunk of Class library C, which needs Config Updates Y and Z and Database Update D, which needs Migration Script E... It gets even more complex - like making sure each developer's project is actually compatible with the others and are building against the same versions. Yes, this is a management issue as much as a technical issue. Currently our non-optimal solution is: a whiteboard listing features that haven't gone live yet relying on our memory and intuition when planning the rollout, until we're pretty sure we've thought of everything... a dry-run on our Staging environment. It's a good indication but we're often not sure if Staging is 100% in sync with Live - part of the problem I'm hoping to solve. some amount of winging it on rollout day. So far so good, minus a few close calls. But as our system grows, I'd like a more scientific release management system allowing for more flexibility, like being able to roll out a single change or bugfix on it's own, safe in the knowledge that it won't break anything else. I'm guessing the best solution involves some sort of version numbering system, and perhaps using a project management tool. We're a start-up, so we're not too hot on religiously sticking to rigid processes, but we're happy to start, providing it doesn't add more overhead than it's worth. I'd love to hear advice from other teams who have solved this problem.

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• List of objects or parallel arrays of properties?

  - by Headcrab

  The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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• What is faster- Java or C# (Or good old C)?

  - by Rexsung

  I'm currently deciding on a platform to build a scientific computational product on, and am deciding on either C#, Java, or plain C with Intels compiler on Core2 Quad CPU's. It's mostly integer arithmetic. My benchmarks so far show Java and C are about on par with each other, and dotNET/C# trails by about 5%- however a number of my coworkers are claiming that dotNET with the right optimizations will beat both of these given enough time for the JIT to do its work. I always assume that the JIT would have done it's job within a few minutes of the app starting (Probably a few seconds in my case, as it's mostly tight loops), so I'm not sure whether to believe them Can anyone shed any light on the situation? Would dotNET beat Java? (Or am I best just sticking with C at this point?). The code is highly multithreaded and data sets are several terabytes in size. Haskell/erlang etc are not options in this case as there is a significant quantity of existing legacy C code that will be ported to the new system, and porting C to Java/C# is a lot simpler than to Haskell or Erlang. (Unless of course these provide a significant speedup). Edit: We are considering moving to C# or Java because they may, in theory, be faster. Every percent we can shave off our processing time saves us tens of thousands of dollars per year. At this point we are just trying to evaluate whether C, Java, or c# would be faster.

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• C# COM Cross Thread problem

  - by user364676

  Hi, we're developing a software to control a scientific measuring device. it provides a COM-Interface defines serveral functions to set measurement parameters and fires an event when it measured data. in order to test our software, i'm implementing a simulation of that device. the com-object runs a loop which periodically fires the event. another loop in the client app should now setup up the com-simulator using the given functions. i created a class for measuring parameters which will be instanciated when setting up a new measurement. // COM-Object public class MeasurementParams { public double Param1; public double Param2; } public class COM_Sim : ICOMDevice { public MeasurementParams newMeasurement; IClient client; public int NewMeasurement() { newMeasurment = new MeasurementParam(); } public int SetParam1(double val) { // why is newMeasurement null when method is called from client loop newMeasurement.Param1 = val; } void loop() { while(true) { // fire event client.HandleEvent; } } } public class Client : IClient { ICOMDevice server; public int HandleEvent() { // handle this event server.NewMeasurement(); server.SetParam1(0.0); } void loop() { while(true) { // do some stuff... server.NewMeasurement(); server.SetParam1(0.0); } } } both of the loops run in independent threads. when server.NewMeasurement() is called, the object on the server is set to a new instance. but in the next function, the object is null again. do the same when handling the server-event, it works perfectly, because the method runs in the servers thread. how to make it work from client-thread as well. as the client is meant to be working with the real device, i cannot modify the interfaces given by the manufactor. also i need to setup measurements independent from the event-handler, which will be fired not regulary. i assume this problem related to multithreaded-COM behavior but i found nothing on this topic.

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• Something is wrong with my C++ compilers [on hold]

  - by Karol Turbiarz

  WARNING!!! IT IS C++ but it uses domath ant rootBase LIBRARY, SOE I CAN MAKE SQARE ROOTS, AND OTHEr STUFF LIKE SIN, COS!!!!!! #include <iostream> #include <cstdio> #include <h.2> #include <time> #include <math> #include <domath> #include <rootBase> Then my code doesn't have any error (by the way I'm doing scientific calculator with squared root, line graphing, sin, cos, etc..) but then ... My debbuger finds problem here: if(math1 !== math2); MathCouldNotReadVoid2(); Which goes to void: void MathCouldNotReadVoid2(); { if(math1 ==! (math3 - math2)) { float decimalpoint(); using namespace std; using namespace fc; SquaredRoot(); float SquaredRootExponents(0.07839947388); float SquaredRootExponentFormForRootFormula((SquaredRootExponents *==)+ PiV); float SqRootFormulaStepOnePISHORTCUT(>=3.14'>DoMath<'<=7.2 * FgYt2 + 7.1107); } else main(); } That's the only one of my couple steps, for SquaredRoot, but it doesn't define the "=3.14'DoMath<'<=7.2*FgYt2+7.1107" step. I know some people may not know this type of "command" from the 'rootBase' library, but maybe some of you may know... Please help...Thanks.

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• how to place social media links at the end of every TYPO3 content element?

  - by Ugur Koçak

  Thanks to Kasper Skårhøj and all TYPO3 developers for this great product and extensions. I am a TYPO3 user and want to build a scientific portal using TYPO3-YAML. I use the package tyaml_2.0.1_complete from if-20 Project. It includes TYPO3 4.7.4 + YAML and many extensions. Facebook like button, Twitter and G+ buttons have been integrated to News extension by Georg Ringer. What I need is; I want to place the same buttons (fblike, fbshare, twitter and G+) buttons at the end of every content element automatically. I am searching web for more than 2 weeks, and read many pages about it, but all of them are for the coders. I couldn't find a solution yet.I can apply them if all steps are written one by one, and clearly. For example; http://www.typo3tutorials.net/2012/06/typoscript-wrap-content-elemtents-with.html But my TYPO3 package uses fluid template and don't know how to apply it exactly. Please could you give me a link (in any language) explaining how to integrate these buttons to the end of "text" or "text with image" ce? Or can you write them step by step. Thanks much.

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• how would you like computer science classes to be taught?

  - by aaa

  hello I am a graduate student now, and hopefully someday I will teach. my interests are C++, Python, embedded languages, and scientific computing. Meanwhile I daydream about how I would teach. I was not quite happy with my undergraduate university as I found many computer science classes lacking. so I would like to ask you, if you were a student, how would you like your computer science classes to be taught? I understand it is a very subjective question, but nevertheless I think it's important to know what people want. Some specific points I am interested in: should computer languages be taught explicitly, or should students be required to pick up language on their own? what is better for learning, tests, projects, some sort of take-home exam? how do you think classtime should be used? theory, introduction, explanations, etc.? do you think the group projects are important? how much about computer architecture do you want to learn in computer science class, not necessarily assembler class. should particular operating system/editor be mandated or encouraged? Thanks thank you for your comments. Question has been closed because it is a discussion question rather than Q&A. If you know appropriate website for discussions of such sort with low noise ratio, please let me know.

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• Populating a foreign key table with variable user input

  - by Vincent

  I'm working on a website that will be based on user contributed data, submitted using a regular HTML form. To simplify my question, let's say that there will be two fields in the form: "User Name" and "Country" (this is just an example, not the actual site). There will be two tables in the database : "countries" and "users," with "users.country_id" being a foreign key to the "countries" table (one-to-many). The initial database will be empty. Users from all over the world will submit their names and the countries they live in and eventually the "countries" table will get filled out with all of the country names in the world. Since one country can have several alternative names, input like Chile, Chili, Chilli will generate 3 different records in the countries table, but in fact there is only one country. When I search for records from Chile, Chili and Chilli will not be included. So my question is - what would be the best way to deal with a situation like this, with conditions such that the initial database is empty, no other resources are available and everything is based on user input? How can I organize it in such way that Chile, Chili and Chilli would be treated as one country, with minimum manual interference. What are the best practices when it comes to normalizing user submitted data and is there a scientific term for this? I'm sure this is a common problem. Again, I used country names just to simplify my question, it can be anything that has possible different spellings.

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