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• SSL certificate for Oracle Application Server 11g

  - by Easter Sunshine

  I was asked to get an SSL certificate for an "Oracle Application Server 11g" which has a soon-to-expire certificate. Brushing aside the fact that 10g seems to be the newest version, I got a certificate from InCommon, as I usually do without problem (except this is the first time I supplied Oracle Application Server 11g as the software type on the CSR form). On the email containing links to download the certificate, it mentioned: Certificate Details: SSL Type : InCommon SSL Server : OTHER I forwarded the email over to the person responsible for installing it and got a reply that the server type must be Oracle Application Server for the certificate to work (the CN is the same as before). They were unable to install this certificate (no details provided to me) and mentioned they had this issue previously with Thawte when they didn't supply Oracle Application Server as the server type. I don't see any significant difference between the currently installed certificate (working) and the new one I just got signed by InCommon (not working). $ openssl x509 -in sso-current.cer -text shows, with irrelevant information ommitted. Data: Version: 3 (0x2) Signature Algorithm: sha1WithRSAEncryption Issuer: C=ZA, ST=Western Cape, L=Cape Town, O=Thawte Consulting cc, OU=Certification Services Division, CN=Thawte Premium Server CA/[email protected] Validity Not Before: Oct 1 00:00:00 2009 GMT Not After : Nov 28 23:59:59 2012 GMT Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: critical CA:FALSE X509v3 CRL Distribution Points: Full Name: URI:http://crl.thawte.com/ThawteServerPremiumCA.crl X509v3 Extended Key Usage: TLS Web Server Authentication, TLS Web Client Authentication Authority Information Access: OCSP - URI:http://ocsp.thawte.com Signature Algorithm: sha1WithRSAEncryption and $ openssl x509 -in sso-new.cer -text shows Data: Version: 3 (0x2) Signature Algorithm: sha1WithRSAEncryption Issuer: C=US, O=Internet2, OU=InCommon, CN=InCommon Server CA Validity Not Before: Nov 8 00:00:00 2012 GMT Not After : Nov 8 23:59:59 2014 GMT Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Authority Key Identifier: keyid:48:4F:5A:FA:2F:4A:9A:5E:E0:50:F3:6B:7B:55:A5:DE:F5:BE:34:5D X509v3 Subject Key Identifier: 18:8D:F6:F5:87:4D:C4:08:7B:2B:3F:02:A1:C7:AC:6D:A7:90:93:02 X509v3 Key Usage: critical Digital Signature, Key Encipherment X509v3 Basic Constraints: critical CA:FALSE X509v3 Extended Key Usage: TLS Web Server Authentication, TLS Web Client Authentication X509v3 Certificate Policies: Policy: 1.3.6.1.4.1.5923.1.4.3.1.1 CPS: https://www.incommon.org/cert/repository/cps_ssl.pdf X509v3 CRL Distribution Points: Full Name: URI:http://crl.incommon.org/InCommonServerCA.crl Authority Information Access: CA Issuers - URI:http://cert.incommon.org/InCommonServerCA.crt OCSP - URI:http://ocsp.incommon.org Nothing jumps out at me as the reason one would not work so I don't have a specific request for the signer for what to do differently when re-signing.

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• SQL SERVER – When are Statistics Updated – What triggers Statistics to Update

  - by pinaldave

  If you are an SQL Server Consultant/Trainer involved with Performance Tuning and Query Optimization, I am sure you have faced the following questions many times. When is statistics updated? What is the interval of Statistics update? What is the algorithm behind update statistics? These are the puzzling questions and more. I searched the Internet as well many official MS documents in order to find answers. All of them have provided almost similar algorithm. However, at many places, I have seen a bit of variation in algorithm as well. I have finally compiled the list of various algorithms and decided to share what was the most common “factor” in all of them. I would like to ask for your suggestions as whether following the details, when Statistics is updated, are accurate or not. I will update this blog post with accurate information after receiving your ideas. The answer I have found here is when statistics are expired and not when they are automatically updated. I need your help here to answer when they are updated. Permanent table If the table has no rows, statistics is updated when there is a single change in table. If the number of rows in a table is less than 500, statistics is updated for every 500 changes in table. If the number of rows in table is more than 500, statistics is updated for every 500+20% of rows changes in table. Temporary table If the table has no rows, statistics is updated when there is a single change in table. If the number of rows in table is less than 6, statistics is updated for every 6 changes in table. If the number of rows in table is less than 500, statistics is updated for every 500 changes in table. If the number of rows in table is more than 500, statistics is updated for every 500+20% of rows changes in table. Table variable There is no statistics for Table Variables. If you want to read further about statistics, I suggest that you read the white paper Statistics Used by the Query Optimizer in Microsoft SQL Server 2008. Let me know your opinions about statistics, as well as if there is any update in the above algorithm. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Question, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL Statistics

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• SQLAuthority News – Links to Book On Line – Data Mining Algorithms (Analysis Services – Data Mining)

  - by pinaldave

  I have quite often received request for the Data Mining Algorithms details. Book Online has wonderful resources for the same. I suggest to read them here. Data Mining Algorithms (Analysis Services – Data Mining) The data mining algorithm is the mechanism that creates a data mining model. To create a model, an algorithm first analyzes a set [...]

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• XNA running slow when making a texture

  - by Anthony

  I'm using XNA to test an image analysis algorithm for a robot. I made a simple 3D world that has a grass, a robot, and white lines (that are represent the course). The image analysis algorithm is a modification of the Hough line detection algorithm. I have the game render 2 camera views to a render target in memory. One camera is a top down view of the robot going around the course, and the second camera is the view from the robot's perspective as it moves along. I take the rendertarget of the robot camera and convert it to a Color[,] so that I can do image analysis on it. private Color[,] TextureTo2DArray(Texture2D texture, Color[] colors1D, Color[,] colors2D) { texture.GetData(colors1D); for (int x = 0; x < texture.Width; x++) { for (int y = 0; y < texture.Height; y++) { colors2D[x, y] = colors1D[x + (y * texture.Width)]; } } return colors2D; } I want to overlay the results of the image analysis on the robot camera view. The first part of the image analysis is finding the white pixels. When I find the white pixels I create a bool[,] array showing which pixels were white and which were black. Then I want to convert it back into a texture so that I can overlay on the robot view. When I try to create the new texture showing which ones pixels were white, then the game goes super slow (around 10 hz). Can you give me some pointers as to what to do to make the game go faster. If I comment out this algorithm, then it goes back up to 60 hz. private Texture2D GenerateTexturesFromBoolArray(bool[,] boolArray,Color[] colorMap, Texture2D textureToModify) { for(int i =0;i < screenWidth;i++) { for(int j =0;j<screenHeight;j++) { if (boolArray[i, j] == true) { colorMap[i+(j*screenWidth)] = Color.Red; } else { colorMap[i + (j * screenWidth)] = Color.Transparent; } } } textureToModify.SetData<Color>(colorMap); return textureToModify; } Each Time I run draw, I must set the texture to null, so that I can modify it. public override void Draw(GameTime gameTime) { Vector2 topRightVector = ((SimulationMain)Game).spriteRectangleManager.topRightVector; Vector2 scaleFactor = ((SimulationMain)Game).config.scaleFactorScreenSizeToWindow; this.spriteBatch.Begin(); // Start the 2D drawing this.spriteBatch.Draw(this.textureFindWhite, topRightVector, null, Color.White, 0, Vector2.Zero, scaleFactor, SpriteEffects.None, 0); this.spriteBatch.End(); // Stop drawing. GraphicsDevice.Textures[0] = null; } Thanks for the help, Anthony G.

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• Voxel Face Crawling (Mesh simplification, possibly using greedy)

  - by Tim Winter

  This is in regards to a Minecraft-like terrain engine. I store blocks in chunks (16x256x16 blocks in a chunk). When I generate a chunk, I use multiple procedural techniques to set the terrain and to place objects. While generating, I keep one 1D array for the full chunk (solid or not) and a separate 1D array of solid blocks. After generation, I iterate through the solid blocks checking their neighbors so I only generate block faces that don't have solid neighbors. I store which faces to generate in their own list (that's 6 lists, one per possible face). When rendering a chunk, I render all lists in the camera's current chunk and only the lists facing the camera in all other chunks. Using a 2D atlas with this little shader trick Andrew Russell suggested, I want to merge similar faces together completely. That is, if they are in the same list (same normal), are adjacent to each other, have the same light level, etc. My assumption would be to have each of the 6 lists sorted by the axis they rest on, then by the other two axes (the list for the top of a block would be sorted by it's Y value, then X, then Z). With this alone, I could quite easily merge strips of faces, but I'm looking to merge more than just strips together when possible. I've read up on this greedy meshing algorithm, but I am having a lot of trouble understanding it. To even use it, I would think I'd need to perform a type of flood-fill per sorted list to get the groups of merge-able faces. Then, per group, perform the greedy algorithm. It all sounds awfully expensive if I would ever want dynamic terrain/lighting after initial generation. So, my question: To perform merging of faces as described (ignoring whether it's a bad idea for dynamic terrain/lighting), is there perhaps an algorithm that is simpler to implement? I would also quite happily accept an answer that walks me through the greedy algorithm in a much simpler way (a link or explanation). I don't mind a slight performance decrease if it's easier to implement or even if it's only a little better than just doing strips. I worry that most algorithms focus on triangles rather than quads and using a 2D atlas the way I am, I don't know that I could implement something triangle based with my current skills. PS: I already frustum cull per chunk and as described, I also cull faces between solid blocks. I don't occlusion cull yet and may never.

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• What are algorithmic paradigms?

  - by Vaibhav Agarwal

  We generally talk about paradigms of programming as functional, procedural, object oriented, imperative etc but what should I reply when I am asked the paradigms of algorithms? For example are Travelling Salesman Problem, Dijkstra Shortest Path Algorithm, Euclid GCD Algorithm, Binary search, Kruskal's Minimum Spanning Tree, Tower of Hanoi paradigms of algorithms? Should I answer the data structures I would use to design these algorithms?

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• How can I plot a radius of all reachable points with pathfinding for a Mob?

  - by PugWrath

  I am designing a tactical turn based game. The maps are 2d, but do have varying level-layers and blocking objects/terrain. I'm looking for an algorithm for pathfinding which will allow me to show an opaque shape representing all of the possible max-distance pixels that a mob can move to, knowing the mob's max pixel distance. Any thoughts on this, or do I just need to write a good pathfinding algorithm and use it to find the cutoff points for any direction in which an obstacle exists?

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• Basics of Machine Learning

  - by user1263514

  I am going through Machine Learning algorithms since a week. And there are some doubts that I have in my mind regarding ML. Here are some of the basic questions that I need answers for What are the basic criterias for selecting any Clustering Algorithm? What are the factors affecting the Performance of any Algorithm and any ways to improve them? Please give me some idea as to how do I cope up with these basic questions.

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• What is a useful pattern to maintaining an object state in a one to many relationship?

  - by ahenderson

  I am looking for a design for my application, here are the players(classes) involved. struct Transform { // Uses a matrix to transform the position. // Also acts acts as the state of a Dialog. Position transform(Position p); //other methods. }; struct Dialog { // There are multiple dialog for the user to transform the output. Transform& t; void ChangeTranformation(){t.rotate(360);} } struct Algorithm { //gives us a position based on an implementation. For example this can return points on a circle or line. Transform& t; Position m_p; Dialog& d; Position GetCurrentPosition(){ return t.transform(m_p);} //other methods. } Properties I need: Each algorithms has one dialog and each dialog can have many algorithms associated with it. When the user selects an algorithm a dialog associated with that algorithm is displayed. If the user selects a different algorithm then re-selects back the state is restored in the dialog. Basically I want a good design pattern to maintain the state of the dialog given that many algorithms use it and they can be switched back and forth. Does anyone have any suggestions? Here is a use case: Dialog1 has a single edit box to control the radius. Algorithm1 generates points on a unit circle. Algorithm2 is the same as Algorithm1. The user has selected Algorithm1 and entered 2 into the edit box. This will generate points on a circle of radius 2. The user then selects Algorithm2 and enters 10 into the edit box of Dialog1. This will generate points on a circle of radius 10. Finally Algorithm1 is selected again. The edit box of Dialog1 should show 2 and points on a circle of radius 2 should be generated.

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• META Tags in SEO - Should You Use Them?

  Onsite SEO is going by the wayside and not being used by the search engines much anymore but it may still benefit you to optimize each of your web pages. The search engines have a formula to determine keyword relevancy on each page of your web site. The technical term is an algorithm, which each engine has its own unique algorithm that it uses to rank pages.

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• What is Google Page Rank and Why is it So Important?

  What exactly is PageRank? It is basically a link analysis algorithm, which was influenced by citation analysis, which dates way back to the fifties, when it was conceived by Eugene Garfield and later on by Massimo Marchiori. This link analysis algorithm essentially gives set of hyperlinked documents, where they are weighed in numerical form, and are given a number assignment between zero to ten.

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• How can I plot a radius of all reachable points with pathfinding for a Mob (XNA)?

  - by PugWrath

  I am designing a tactical turn based game. The maps are 2d, but do have varying level-layers and blocking objects/terrain. I'm looking for an algorithm for pathfinding which will allow me to show an opaque shape representing all of the possible max-distance pixels that a mob can move to, knowing the mob's max pixel distance. Any thoughts on this, or do I just need to write a good pathfinding algorithm and use it to find the cutoff points for any direction in which an obstacle exists?

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• What's the most useful piece of logic you use? [closed]

  - by nomaderWhat

  Just tapping away and automatically made use of that one logic algorithm I always use, which you'll probably guess is: (not A) OR (not B) = not (A AND B) Curious if this is the case for just about everyone else, and more curious if there is a different algorithm that other programmers make use of that is just as if not more useful to them. Really hoping for the latter, cause the one above is well... so boring.

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• SEO News - Mayday One Month On

  What affect has the 'Mayday' change to Google's Algorithm had to your Longtail SEO campaign? For the uninitiated, and I am sure there are many, I will just explain what I mean by 'Mayday'. At the end of April / beginning of May Google made a 'slight' change to its algorithm.

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• In WCF How Can I add SAML 2.0 assertion to SOAP Header?

  - by Tone

  I'm trying to add the saml 2.0 assertion node from the soap header example below - I came across the samlassertion type in the .net framework but that looks like it is only for saml 1.1. <S:Header> <To xmlns="http://www.w3.org/2005/08/addressing">https://rs1.greenwaymedical.com:8181/CONNECTGateway/EntityService/NhincProxyXDRRequestSecured</To> <Action xmlns="http://www.w3.org/2005/08/addressing">tns:ProvideAndRegisterDocumentSet-bRequest_Request</Action> <ReplyTo xmlns="http://www.w3.org/2005/08/addressing"> <Address>http://www.w3.org/2005/08/addressing/anonymous</Address> </ReplyTo> <MessageID xmlns="http://www.w3.org/2005/08/addressing">uuid:662ee047-3437-4781-a8d2-ee91bc940ef0</MessageID> <wsse:Security S:mustUnderstand="1"> <wsu:Timestamp xmlns:ns17="http://docs.oasis-open.org/ws-sx/ws-secureconversation/200512" xmlns:ns16="http://www.w3.org/2003/05/soap-envelope" wsu:Id="_1"> <wsu:Created>2010-05-26T03:51:57Z</wsu:Created> <wsu:Expires>2010-05-26T03:56:57Z</wsu:Expires> </wsu:Timestamp> <saml2:Assertion xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:exc14n="http://www.w3.org/2001/10/xml-exc-c14n#" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" xmlns:xs="http://www.w3.org/2001/XMLSchema" ID="bd1ecf8d-a6d8-488d-9183-a11227c6a219" IssueInstant="2010-05-26T03:51:57.959Z" Version="2.0"> <saml2:Issuer Format="urn:oasis:names:tc:SAML:1.1:nameid-format:X509SubjectName">CN=SAML User,OU=SU,O=SAML User,L=Los Angeles,ST=CA,C=US</saml2:Issuer> <saml2:Subject> <saml2:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:X509SubjectName">UID=kskagerb</saml2:NameID> <saml2:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:holder-of-key"> <saml2:SubjectConfirmationData> <ds:KeyInfo> <ds:KeyValue> <ds:RSAKeyValue> <ds:Modulus>p4jUkEUg..gwO7U=</ds:Modulus> <ds:Exponent>AQAB</ds:Exponent> </ds:RSAKeyValue> </ds:KeyValue> </ds:KeyInfo> </saml2:SubjectConfirmationData> </saml2:SubjectConfirmation> </saml2:Subject> <saml2:AuthnStatement AuthnInstant="2009-04-16T13:15:39.000Z" SessionIndex="987"> <saml2:SubjectLocality Address="158.147.185.168" DNSName="cs.myharris.net"/> <saml2:AuthnContext> <saml2:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:X509</saml2:AuthnContextClassRef> </saml2:AuthnContext> </saml2:AuthnStatement> <saml2:AttributeStatement> <saml2:Attribute Name="urn:oasis:names:tc:xspa:1.0:subject:subject-id"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">Karl S Skagerberg</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xspa:1.0:subject:organization"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">InternalTest2</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xspa:1.0:subject:organization-id"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">2.2</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:nhin:names:saml:homeCommunityId"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">2.16.840.1.113883.3.441</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xacml:2.0:subject:role"> <saml2:AttributeValue> <hl7:Role xmlns:hl7="urn:hl7-org:v3" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" code="307969004" codeSystem="2.16.840.1.113883.6.96" codeSystemName="SNOMED_CT" displayName="Public Health" xsi:type="hl7:CE"/> </saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xspa:1.0:subject:purposeofuse"> <saml2:AttributeValue> <hl7:PurposeForUse xmlns:hl7="urn:hl7-org:v3" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" code="PUBLICHEALTH" codeSystem="2.16.840.1.113883.3.18.7.1" codeSystemName="nhin-purpose" displayName="Use or disclosure of Psychotherapy Notes" xsi:type="hl7:CE"/> </saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xacml:2.0:resource:resource-id"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">500000000^^^&amp;1.1&amp;ISO</saml2:AttributeValue> </saml2:Attribute> </saml2:AttributeStatement> <saml2:AuthzDecisionStatement Decision="Permit" Resource="https://158.147.185.168:8181/SamlReceiveService/SamlProcessWS"> <saml2:Action Namespace="urn:oasis:names:tc:SAML:1.0:action:rwedc">Execute</saml2:Action> <saml2:Evidence> <saml2:Assertion ID="40df7c0a-ff3e-4b26-baeb-f2910f6d05a9" IssueInstant="2009-04-16T13:10:39.093Z" Version="2.0"> <saml2:Issuer Format="urn:oasis:names:tc:SAML:1.1:nameid-format:X509SubjectName">CN=SAML User,OU=Harris,O=HITS,L=Melbourne,ST=FL,C=US</saml2:Issuer> <saml2:Conditions NotBefore="2009-04-16T13:10:39.093Z" NotOnOrAfter="2009-12-31T12:00:00.000Z"/> <saml2:AttributeStatement> <saml2:Attribute Name="AccessConsentPolicy" NameFormat="http://www.hhs.gov/healthit/nhin"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">Claim-Ref-1234</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="InstanceAccessConsentPolicy" NameFormat="http://www.hhs.gov/healthit/nhin"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">Claim-Instance-1</saml2:AttributeValue> </saml2:Attribute> </saml2:AttributeStatement> </saml2:Assertion> </saml2:Evidence> </saml2:AuthzDecisionStatement> <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"> <ds:SignedInfo> <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/> <ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/> <ds:Reference URI="#bd1ecf8d-a6d8-488d-9183-a11227c6a219"> <ds:Transforms> <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/> <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/> </ds:Transforms> <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/> <ds:DigestValue>ONbZqPUyFVPMx4v9vvpJGNB4cao=</ds:DigestValue> </ds:Reference> </ds:SignedInfo> <ds:SignatureValue>Dm/aW5bB..pF93s=</ds:SignatureValue> <ds:KeyInfo> <ds:KeyValue> <ds:RSAKeyValue> <ds:Modulus>p4jUkEU..bzqgwO7U=</ds:Modulus> <ds:Exponent>AQAB</ds:Exponent> </ds:RSAKeyValue> </ds:KeyValue> </ds:KeyInfo> </ds:Signature> </saml2:Assertion> <ds:Signature xmlns:ns17="http://docs.oasis-open.org/ws-sx/ws-secureconversation/200512" xmlns:ns16="http://www.w3.org/2003/05/soap-envelope" Id="_2"> <ds:SignedInfo> <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"> <exc14n:InclusiveNamespaces PrefixList="wsse S"/> </ds:CanonicalizationMethod> <ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/> <ds:Reference URI="#_1"> <ds:Transforms> <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"> <exc14n:InclusiveNamespaces PrefixList="wsu wsse S"/> </ds:Transform> </ds:Transforms> <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/> <ds:DigestValue> <Include xmlns="http://www.w3.org/2004/08/xop/include" href="cid:[email protected]"/> </ds:DigestValue> </ds:Reference> </ds:SignedInfo> <ds:SignatureValue> <Include xmlns="http://www.w3.org/2004/08/xop/include" href="cid:[email protected]"/> </ds:SignatureValue> <ds:KeyInfo> <wsse:SecurityTokenReference wsse11:TokenType="http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLV2.0"> <wsse:KeyIdentifier ValueType="http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLID">bd1ecf8d-a6d8-488d-9183-a11227c6a219</wsse:KeyIdentifier> </wsse:SecurityTokenReference> </ds:KeyInfo> </ds:Signature> </wsse:Security> </S:Header> I've been researching for days and cannot seem to come up with a straightforward way of doing this in WCF. The web service is running on Glassfish and is soap 1.1, I've tried using all the packaged wcf bindings but have not been able to get them to work. I started down the path of using a MessageInspector, and wrote one but then realized there must be a better way, surely WCF provides some way to insert saml 2.0 assertions. I've made the most progress writing a custom binding - i've been able to get the timestamp and signature nodes in the soap header, but cannot for the life of me figure out the saml assertion. Any ideas? public static System.ServiceModel.Channels.Binding BuildCONNECTCustomBinding() { TransportSecurityBindingElement transportSecurityBindingElement = SecurityBindingElement.CreateCertificateOverTransportBindingElement(MessageSecurityVersion.WSSecurity10WSTrustFebruary2005WSSecureConversationFebruary2005WSSecurityPolicy11BasicSecurityProfile10); TextMessageEncodingBindingElement textMessageEncodingBindingElement = new TextMessageEncodingBindingElement(MessageVersion.Soap11WSAddressing10, System.Text.Encoding.UTF8); HttpsTransportBindingElement httpsTransportBindingElement = new HttpsTransportBindingElement(); SecurityTokenReferenceType securityTokenReference = new SecurityTokenReferenceType(); BindingElementCollection bindingElementCollection = new BindingElementCollection(); bindingElementCollection.Add(transportSecurityBindingElement); bindingElementCollection.Add(textMessageEncodingBindingElement); bindingElementCollection.Add(httpsTransportBindingElement); CustomBinding cb = new CustomBinding(bindingElementCollection); cb.CreateBindingElements(); return cb; }

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• In a WCF Client How Can I add SAML 2.0 assertion to SOAP Header?

  - by Tone

  I'm trying to add the saml 2.0 assertion node from the soap header example below - I came across the samlassertion type in the .net framework but that looks like it is only for saml 1.1. <S:Header> <To xmlns="http://www.w3.org/2005/08/addressing">https://rs1.greenwaymedical.com:8181/CONNECTGateway/EntityService/NhincProxyXDRRequestSecured</To> <Action xmlns="http://www.w3.org/2005/08/addressing">tns:ProvideAndRegisterDocumentSet-bRequest_Request</Action> <ReplyTo xmlns="http://www.w3.org/2005/08/addressing"> <Address>http://www.w3.org/2005/08/addressing/anonymous</Address> </ReplyTo> <MessageID xmlns="http://www.w3.org/2005/08/addressing">uuid:662ee047-3437-4781-a8d2-ee91bc940ef0</MessageID> <wsse:Security S:mustUnderstand="1"> <wsu:Timestamp xmlns:ns17="http://docs.oasis-open.org/ws-sx/ws-secureconversation/200512" xmlns:ns16="http://www.w3.org/2003/05/soap-envelope" wsu:Id="_1"> <wsu:Created>2010-05-26T03:51:57Z</wsu:Created> <wsu:Expires>2010-05-26T03:56:57Z</wsu:Expires> </wsu:Timestamp> <saml2:Assertion xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:exc14n="http://www.w3.org/2001/10/xml-exc-c14n#" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" xmlns:xs="http://www.w3.org/2001/XMLSchema" ID="bd1ecf8d-a6d8-488d-9183-a11227c6a219" IssueInstant="2010-05-26T03:51:57.959Z" Version="2.0"> <saml2:Issuer Format="urn:oasis:names:tc:SAML:1.1:nameid-format:X509SubjectName">CN=SAML User,OU=SU,O=SAML User,L=Los Angeles,ST=CA,C=US</saml2:Issuer> <saml2:Subject> <saml2:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:X509SubjectName">UID=kskagerb</saml2:NameID> <saml2:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:holder-of-key"> <saml2:SubjectConfirmationData> <ds:KeyInfo> <ds:KeyValue> <ds:RSAKeyValue> <ds:Modulus>p4jUkEUg..gwO7U=</ds:Modulus> <ds:Exponent>AQAB</ds:Exponent> </ds:RSAKeyValue> </ds:KeyValue> </ds:KeyInfo> </saml2:SubjectConfirmationData> </saml2:SubjectConfirmation> </saml2:Subject> <saml2:AuthnStatement AuthnInstant="2009-04-16T13:15:39.000Z" SessionIndex="987"> <saml2:SubjectLocality Address="158.147.185.168" DNSName="cs.myharris.net"/> <saml2:AuthnContext> <saml2:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:X509</saml2:AuthnContextClassRef> </saml2:AuthnContext> </saml2:AuthnStatement> <saml2:AttributeStatement> <saml2:Attribute Name="urn:oasis:names:tc:xspa:1.0:subject:subject-id"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">Karl S Skagerberg</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xspa:1.0:subject:organization"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">InternalTest2</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xspa:1.0:subject:organization-id"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">2.2</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:nhin:names:saml:homeCommunityId"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">2.16.840.1.113883.3.441</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xacml:2.0:subject:role"> <saml2:AttributeValue> <hl7:Role xmlns:hl7="urn:hl7-org:v3" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" code="307969004" codeSystem="2.16.840.1.113883.6.96" codeSystemName="SNOMED_CT" displayName="Public Health" xsi:type="hl7:CE"/> </saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xspa:1.0:subject:purposeofuse"> <saml2:AttributeValue> <hl7:PurposeForUse xmlns:hl7="urn:hl7-org:v3" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" code="PUBLICHEALTH" codeSystem="2.16.840.1.113883.3.18.7.1" codeSystemName="nhin-purpose" displayName="Use or disclosure of Psychotherapy Notes" xsi:type="hl7:CE"/> </saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="urn:oasis:names:tc:xacml:2.0:resource:resource-id"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">500000000^^^&amp;1.1&amp;ISO</saml2:AttributeValue> </saml2:Attribute> </saml2:AttributeStatement> <saml2:AuthzDecisionStatement Decision="Permit" Resource="https://158.147.185.168:8181/SamlReceiveService/SamlProcessWS"> <saml2:Action Namespace="urn:oasis:names:tc:SAML:1.0:action:rwedc">Execute</saml2:Action> <saml2:Evidence> <saml2:Assertion ID="40df7c0a-ff3e-4b26-baeb-f2910f6d05a9" IssueInstant="2009-04-16T13:10:39.093Z" Version="2.0"> <saml2:Issuer Format="urn:oasis:names:tc:SAML:1.1:nameid-format:X509SubjectName">CN=SAML User,OU=Harris,O=HITS,L=Melbourne,ST=FL,C=US</saml2:Issuer> <saml2:Conditions NotBefore="2009-04-16T13:10:39.093Z" NotOnOrAfter="2009-12-31T12:00:00.000Z"/> <saml2:AttributeStatement> <saml2:Attribute Name="AccessConsentPolicy" NameFormat="http://www.hhs.gov/healthit/nhin"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">Claim-Ref-1234</saml2:AttributeValue> </saml2:Attribute> <saml2:Attribute Name="InstanceAccessConsentPolicy" NameFormat="http://www.hhs.gov/healthit/nhin"> <saml2:AttributeValue xmlns:ns6="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns7="http://www.w3.org/2001/XMLSchema" ns6:type="ns7:string">Claim-Instance-1</saml2:AttributeValue> </saml2:Attribute> </saml2:AttributeStatement> </saml2:Assertion> </saml2:Evidence> </saml2:AuthzDecisionStatement> <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"> <ds:SignedInfo> <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/> <ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/> <ds:Reference URI="#bd1ecf8d-a6d8-488d-9183-a11227c6a219"> <ds:Transforms> <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/> <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/> </ds:Transforms> <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/> <ds:DigestValue>ONbZqPUyFVPMx4v9vvpJGNB4cao=</ds:DigestValue> </ds:Reference> </ds:SignedInfo> <ds:SignatureValue>Dm/aW5bB..pF93s=</ds:SignatureValue> <ds:KeyInfo> <ds:KeyValue> <ds:RSAKeyValue> <ds:Modulus>p4jUkEU..bzqgwO7U=</ds:Modulus> <ds:Exponent>AQAB</ds:Exponent> </ds:RSAKeyValue> </ds:KeyValue> </ds:KeyInfo> </ds:Signature> </saml2:Assertion> <ds:Signature xmlns:ns17="http://docs.oasis-open.org/ws-sx/ws-secureconversation/200512" xmlns:ns16="http://www.w3.org/2003/05/soap-envelope" Id="_2"> <ds:SignedInfo> <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"> <exc14n:InclusiveNamespaces PrefixList="wsse S"/> </ds:CanonicalizationMethod> <ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/> <ds:Reference URI="#_1"> <ds:Transforms> <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"> <exc14n:InclusiveNamespaces PrefixList="wsu wsse S"/> </ds:Transform> </ds:Transforms> <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/> <ds:DigestValue> <Include xmlns="http://www.w3.org/2004/08/xop/include" href="cid:[email protected]"/> </ds:DigestValue> </ds:Reference> </ds:SignedInfo> <ds:SignatureValue> <Include xmlns="http://www.w3.org/2004/08/xop/include" href="cid:[email protected]"/> </ds:SignatureValue> <ds:KeyInfo> <wsse:SecurityTokenReference wsse11:TokenType="http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLV2.0"> <wsse:KeyIdentifier ValueType="http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLID">bd1ecf8d-a6d8-488d-9183-a11227c6a219</wsse:KeyIdentifier> </wsse:SecurityTokenReference> </ds:KeyInfo> </ds:Signature> </wsse:Security> </S:Header> I've been researching for days and cannot seem to come up with a straightforward way of doing this in WCF. The web service is running on Glassfish and is soap 1.1, I've tried using all the packaged wcf bindings but have not been able to get them to work. I started down the path of using a MessageInspector, and wrote one but then realized there must be a better way, surely WCF provides some way to insert saml 2.0 assertions. I've made the most progress writing a custom binding - i've been able to get the timestamp and signature nodes in the soap header, but cannot for the life of me figure out the saml assertion. Any ideas? public static System.ServiceModel.Channels.Binding BuildCONNECTCustomBinding() { TransportSecurityBindingElement transportSecurityBindingElement = SecurityBindingElement.CreateCertificateOverTransportBindingElement(MessageSecurityVersion.WSSecurity10WSTrustFebruary2005WSSecureConversationFebruary2005WSSecurityPolicy11BasicSecurityProfile10); TextMessageEncodingBindingElement textMessageEncodingBindingElement = new TextMessageEncodingBindingElement(MessageVersion.Soap11WSAddressing10, System.Text.Encoding.UTF8); HttpsTransportBindingElement httpsTransportBindingElement = new HttpsTransportBindingElement(); SecurityTokenReferenceType securityTokenReference = new SecurityTokenReferenceType(); BindingElementCollection bindingElementCollection = new BindingElementCollection(); bindingElementCollection.Add(transportSecurityBindingElement); bindingElementCollection.Add(textMessageEncodingBindingElement); bindingElementCollection.Add(httpsTransportBindingElement); CustomBinding cb = new CustomBinding(bindingElementCollection); cb.CreateBindingElements(); return cb; }

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• Developing Schema Compare for Oracle (Part 5): Query Snapshots

  - by Simon Cooper

  If you've emailed us about a bug you've encountered with the EAP or beta versions of Schema Compare for Oracle, we probably asked you to send us a query snapshot of your databases. Here, I explain what a query snapshot is, and how it helps us fix your bug. Problem 1: Debugging users' bug reports When we started the Schema Compare project, we knew we were going to get problems with users' databases - configurations we hadn't considered, features that weren't installed, unicode issues, wierd dependencies... With SQL Compare, users are generally happy to send us a database backup that we can restore using a single RESTORE DATABASE command on our test servers and immediately reproduce the problem. Oracle, on the other hand, would be a lot more tricky. As Oracle generally has a 1-to-1 mapping between instances and databases, any databases users sent would have to be restored to their own instance. Furthermore, the number of steps required to get a properly working database, and the size of most oracle databases, made it infeasible to ask every customer who came across a bug during our beta program to send us their databases. We also knew that there would be lots of issues with data security that would make it hard to get backups. So we needed an easier way to be able to debug customers issues and sort out what strange schema data Oracle was returning. Problem 2: Test execution time Another issue we knew we would have to solve was the execution time of the tests we would produce for the Schema Compare engine. Our initial prototype showed that querying the data dictionary for schema information was going to be slow (at least 15 seconds per database), and this is generally proportional to the size of the database. If you're running thousands of tests on the same databases, each one registering separate schemas, not only would the tests would take hours and hours to run, but the test servers would be hammered senseless. The solution To solve these, we needed to be able to populate the schema of a database without actually connecting to it. Well, the IDataReader interface is the primary way we read data from an Oracle server. The data dictionary queries we use return their data in terms of simple strings and numbers, which we then process and reconstruct into an object model, and the results of these queries are identical for identical schemas. So, we can record the raw results of the queries once, and then replay these results to construct the same object model as many times as required without needing to actually connect to the original database. This is what query snapshots do. They are binary files containing the raw unprocessed data we get back from the oracle server for all the queries we run on the data dictionary to get schema information. The core of the query snapshot generation takes the results of the IDataReader we get from running queries on Oracle, and passes the row data to a BinaryWriter that writes it straight to a file. The query snapshot can then be replayed to create the same object model; when the results of a specific query is needed by the population code, we can simply read the binary data stored in the file on disk and present it through an IDataReader wrapper. This is far faster than querying the server over the network, and allows us to run tests in a reasonable time. They also allow us to easily debug a customers problem; using a simple snapshot generation program, users can generate a query snapshot that could be sent along with a bug report that we can immediately replay on our machines to let us debug the issue, rather than having to obtain database backups and restore databases to test systems. There are also far fewer problems with data security; query snapshots only contain schema information, which is generally less sensitive than table data. Query snapshots implementation However, actually implementing such a feature did have a couple of 'gotchas' to it. My second blog post detailed the development of the dependencies algorithm we use to ensure we get all the dependencies in the database, and that algorithm uses data from both databases to find all the needed objects - what database you're comparing to affects what objects get populated from both databases. We get information on these additional objects using an appropriate WHERE clause on all the population queries. So, in order to accurately replay the results of querying the live database, the query snapshot needs to be a snapshot of a comparison of two databases, not just populating a single database. Furthermore, although the code population queries (eg querying all_tab_cols to get column information) can simply be passed straight from the IDataReader to the BinaryWriter, we need to hook into and run the live dependencies algorithm while we're creating the snapshot to ensure we get the same WHERE clauses, and the same query results, as if we were populating straight from a live system. We also need to store the results of the dependencies queries themselves, as the resulting dependency graph is stored within the OracleDatabase object that is produced, and is later used to help order actions in synchronization scripts. This is significantly helped by the dependencies algorithm being a deterministic algorithm - given the same input, it will always return the same output. Therefore, when we're replaying a query snapshot, and processing dependency information, we simply have to return the results of the queries in the order we got them from the live database, rather than trying to calculate the contents of all_dependencies on the fly. Query snapshots are a significant feature in Schema Compare that really helps us to debug problems with the tool, as well as making our testers happier. Although not really user-visible, they are very useful to the development team to help us fix bugs in the product much faster than we otherwise would be able to.

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• mod_deflate Supported Encodings for Compression

  - by sparc

  It seems to me, that mod_deflate in Apache 2.2 will always return: Content-Encoding: gzip and never: Content-Encoding: deflate It was explained to me, that although there may be a deflate algorithm, mod_deflate is named after a file-format, in which the algorithm could be any of: gzip, bzip. pkzip Of those three, mod_deflate provides gzip. It seems as though gzip is the most popular and widely-supported algorithm in web browsers, but I know some web servers and proxies do return Content-Encoding: deflate. Aside from the confusion of the module's name, it true that mod_deflate will only return Content-Encoding: gzip? Thank you.

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• How does braking assist of car racing games work?

  - by Ayush Khemka

  There are a lot of PC car racing games around which have this unique driving assist which helps brake your car so that you can safely turn it. While in some games it just an 'assist', it will just help your car brake but won't ensure a safe turn. While in others, the braking assist will help you get a safe turn. I was wondering on what could be the algorithm that is followed to achieve it. A very basic algorithm I could think of was, Pre-determine the braking distance of an ideal car for every turn of the track, depending on the radius of the turn, and then start braking the car accordingly. For example, for a turn of less than 90o, the car would start braking automatically at 50m distance from the start of the turn. A more advanced algorithm, which would ensure a safe turn, could be Pre-determine the speed of the car at the start of each turn, individually for each track, turn and car. Also, pre-determine the deceleration rate of each car individually, which varies because of the car's performance. The braking assist would keep recording the speed of the car at a certain instant of time. Start braking the car appropriately so that the car gets to the exact speed needed at the start of the turn. For example, let the speed of a particular car at the start of a turn 43m in radius, be 120km/h. Let the deceleration rate of the car be 200km/h2. If, at some instant of time, the speed of the car is 200km/h, then the car would automatically start braking at 400m from the start of the turn.

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• Is it illegal to rewrite every line of an open source project in a slightly different way, and use it in a closed source project?

  - by Chris Barry

  There is some code which is GPL or LGPL that I am considering using for an iPhone project. If I took that code (JavaScript) and rewrote it in a different language for use on the iPhone would that be a legal issue? In theory the process that has happened is that I have gone through each line of the project, learnt what it is doing, and then reimplemented the ideas in a new language. To me it seems this is like learning how to implement something, but then reimplementing it separately from the original licence. Therefore you have only copied the algorithm, which arguably you could have learnt from somewhere else other than the original project. Does the licence cover the specific implementation or the algorithm as well? EDIT------ Really glad to see this topic create a good conversation. To give a bit more backing to the project, the code involved does some kind of audio analysis. I believe it is non-trivial to learn or implement, although I was prepared to embark on this task (I'm at the level where I can implement an FFT algorithm, and this was going to go beyond that.) It is a fairly low LOC script, so I didn't think it would be too hard to do a straight port. I really like the idea of rereleasing my port as well as using it in the application. I don't see any problem with that, and it would be a great way to give something back to the community. I was going to add a line about not wanting to discuss the moral issues, but I'm quite glad I didn't as it seems to have fired the debate a bit. I still feel a bit odd about using open source code to learn from. Does this mean that anything one learns from an open source project is not allowed to be used in a closed source project? And how long after or different does an implementation have to be to not be considered violation of the licence? Murky! EDIT 2 -------- Follow up question

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• How to find the average color of an image.

  - by Edward Boyle

  Years ago I was the lead developer of a large Scrapbook Web Site. One of the things I implemented was to allow shoppers to find Scrapbook papers and embellishments of like colors (“more like this color”). Below is the base algorithm I wrote to extract the color from an image. It worked out pretty well. I took the returned values and stored them in an associated table for the products. Yet another algorithm was used to SELECT near matches. This algorithm has turned out to be very handy for me. I have used it for borders and subtle outlined text overlays. I am sure you will find more creative uses for it. Enjoy… private Color GetColor(Bitmap bmp) { int r = 0; int g = 0; int b = 0; Color mColor = System.Drawing.Color.White; for (int i = 1; i < bmp.Width; i++) { for (int x = 1; x < bmp.Height; x++) { mColor = bmp.GetPixel(i, x); r += mColor.R; g += mColor.G; b += mColor.B; } } r = (r / (bmp.Height * bmp.Width)); g = (g / (bmp.Height * bmp.Width)); b = (b / (bmp.Height * bmp.Width)); return System.Drawing.Color.FromArgb(r, g, b); } You could also get the RGB values by passing in the RGB by ref private Color GetColor(ref int r, ref int g, ref int b, Bitmap bmp) but that is a bit much as you can simply get it from the return value: mReturnedColor.R; mReturnedColor.G; mReturnedColor.B;

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• Continuous Physics Engine's Collision Detection Techniques

  - by Griffin

  I'm working on a purely continuous physics engine, and I need to choose algorithms for broad and narrow phase collision detection. "Purely continuous" means I never do intersection tests, but instead want to find ways to catch every collision before it happens, and put each into "planned collisions" stack that is ordered by TOI. Broad Phase The only continuous broad-phase method I can think of is encasing each body in a circle and testing if each circle will ever overlap another. This seems horribly inefficient however, and lacks any culling. I have no idea what continuous analogs might exist for today's discrete collision culling methods such as quad-trees either. How might I go about preventing inappropriate and pointless broad test's such as a discrete engine does? Narrow Phase I've managed to adapt the narrow SAT to a continuous check rather than discrete, but I'm sure there's other better algorithms out there in papers or sites you guys might have come across. What various fast or accurate algorithm's do you suggest I use and what are the advantages / disatvantages of each? Final Note: I say techniques and not algorithms because I have not yet decided on how I will store different polygons which might be concave, convex, round, or even have holes. I plan to make a decision on this based on what the algorithm requires (for instance if I choose an algorithm that breaks down a polygon into triangles or convex shapes I will simply store the polygon data in this form).

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• How to practice object oriented programming?

  - by user1620696

  I've always programmed in procedural languages and currently I'm moving towards object orientation. The main problem I've faced is that I can't see a way to practice object orientation in an effective way. I'll explain my point. When I've learned PHP and C it was pretty easy to practice: it was just matter of choosing something and thinking about an algorithm for that thing. In PHP for example, it was matter os sitting down and thinking: "well, just to practice, let me build one application with an administration area where people can add products". This was pretty easy, it was matter of thinking of an algorithm to register some user, to login the user, and to add the products. Combining these with PHP features, it was a good way to practice. Now, in object orientation we have lots of additional things. It's not just a matter of thinking about an algorithm, but analysing requirements deeper, writing use cases, figuring out class diagrams, properties and methods, setting up dependency injection and lots of things. The main point is that in the way I've been learning object orientation it seems that a good design is crucial, while in procedural languages one vague idea was enough. I'm not saying that in procedural languages we can write good software without design, just that for sake of practicing it is feasible, while in object orientation it seems not feasible to go without a good design, even for practicing. This seems to be a problem, because if each time I'm going to practice I need to figure out tons of requirements, use cases and so on, it seems to become not a good way to become better at object orientation, because this requires me to have one whole idea for an app everytime I'm going to practice. Because of that, what's a good way to practice object orientation?

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• In the days of modern computing, in 'typical business apps' - why does performance matter?

  - by Prog

  This may seem like an odd question to some of you. I'm a hobbyist Java programmer. I have developed several games, an AI program that creates music, another program for painting, and similar stuff. This is to tell you that I have an experience in programming, but not in professional development of business applications. I see a lot of talk on this site about performance. People often debate what would be the most efficient algorithm in C# to perform a task, or why Python is slow and Java is faster, etc. What I'm trying to understand is: why does this matter? There are specific areas of computing where I see why performance matters: games, where tens of thousands of computations are happening every second in a constant-update loop, or low level systems which other programs rely on, such as OSs and VMs, etc. But for the normal, typical high-level business app, why does performance matter? I can understand why it used to matter, decades ago. Computers were much slower and had much less memory, so you had to think carefully about these things. But today, we have so much memory to spare and computers are so fast: does it actually matter if a particular Java algorithm is O(n^2)? Will it actually make a difference for the end users of this typical business app? When you press a GUI button in a typical business app, and behind the scenes it invokes an O(n^2) algorithm, in these days of modern computing - do you actually feel the inefficiency? My question is split in two: In practice, today does performance matter in a typical normal business program? If it does, please give me real-world examples of places in such an application, where performance and optimizations are important.

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• String patterns that can be used to filter and group files

  - by Louis Rhys

  One of our application filters files in certain directory, extract some data from it and export a document from the extracted data. The algorithm for extracting the data depends on the file, and so far we use regex to select the algorithm to be used, for example .*\.txt will be processed by algorithm A, foo[0-5]\.xml will be processed by algo B, etc. However now we need some files to be processed together. For example, in one case we need two files, foo.*\.xml and bar.*\.xml. Part of the information to be extracted exist in the foo file, and the other part in the bar file. Moreover, we need to make sure the wild card is compatible. For example, if there are 6 files foo1.xml foo23.xml bar1.xml bar9.xml bar23.xml foo4.xml I would expect foo1 and bar1 to be identified as a group, and foo23 and bar23 as another group. bar9 and foo4 has no pair, so they will not be treated. Now, since the filter is configured by user, we need to have a pattern that can express the above requirement. I don't think you can express meaning like above in standard regex. (foo|bar).*\.xml will match all 6 file above and we can't identify which file is paired for a particular file. Is there any standard pattern that can express it? Or any idea how to modify regex to support this, that can be implemented easily?

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