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• How to show or direct a business analyst to a data modelling subject?

  - by AaronLS

  Our business analysts pushed hard to collect data through a spreadsheet. I am the programmer responsible for importing that data. Usually when they push hard for something like this, I never know how well it will work out until a few weeks later when I have time assigned to work on the task of programming the import of the data. I have tried to do as much as possible along the way, named ranges, data validations, etc. But I usually don't have time to take a detailed look at all the data and compare to the destination in the database to determine how well it matches up. A lot of times there will be maybe a little table of items that somehow I have to relate to something else in the database, but there are not natural or business keys present that would allow me to do so. Make the best of this, trying to write something that can compare strings and make a best guess at it and then go through the effort of creating interfaces for a user to match the imported data to the destination. I feel like if the business analyst was actually creating a data model, they would be forced to think about these relationships, and have an appreciation for the need of natural or business keys to be part of the spreadsheet for the purposes of smoothly importing the data. The closest they come to business analysis is a big flat list of fields, and that would be fine if it were like any other data dictionary and include data types+relationships, but it isn't. They are just a bunch of names. No indication of what type of data they might hold, and it is up to me to guess. When I have pushed for more detail, they say that it is just busy work. How can I explain the importance of data modelling? How can I tell them what it is and how to do it? It feels impossible, because they don't have an appreciation for its importance. They do however, usually have an interest in helping out in whatever way they can, it's just this in particular has never gotten a motivated response.

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• Should a Parent with Children have a DefaultChild, or should a Child have a Default property?

  - by Stijn

  Which of the following two models makes more sense? I'm leaning towards the first one because there can only be one default child. The examples are in C# but I think it can apply to other languages too. Here DefaultChild holds one of the items in Children. class Parent { int ID { get; set; } Child DefaultChild { get; set; } IEnumerable<Child> Children { get; set; } } class Child { int ID { get; set; } } Here one of the items in Children has Default set to true while the others have it set to false. class Parent { int ID { get; set; } IEnumerable<Child> Children { get; set; } } class Child { int ID { get; set; } bool Default { get; set; } } A concrete situation: a User in our system has one or more Customers attached. When logging in, if said User has a default Customer, they are immediately working under this Customer. If they don't, they have to select a Customer to work under. While logged in, they can switch between Customers.

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• Relationships in a Chen ERD

  - by Nibroc A Rehpotsirhc

  I am working on a Chen ERD to model our organizations merchandise. Our central entity is a Style. We have supplemental entities of Color and Season. I am defining our assortment as the relationship between these three entities, and this relationship itself will have attributes and is defined by the three entities which participate in the mandatory relationship. The rules are; Many Styles can be offered in a Season, and a Style can be offered in many Seasons. Within a Season, a Style can be offered in Many Colors. I then have 2 other entities, one of which I believe is a weak entity, Climate, and the other may be weak, but I am not sure, this being Transaction Channel. I am thinking of these as relationships off of a relationship? Meaning, for a given Style/Color combination offered in a Season, it can be available through 1 or more Transaction Channels. Additionally, within a season, a given Style/Color combination can be intended for 1 or more Climates. Is it valid to have relationships off of relationships? Or does this requirement dictate that I should think of this Style/Color/Season relationship as an entity itself, and define the relationships to Climate and Transaction Channel off of this entity?

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• Mobile phone detection (brand, model, browser etc)

  - by SyaZ

  What do you use to detect visitor's mobile phone, down to the model if possible? Currently we maintain our own database but it's really getting behind due to lack of manpower to maintain it, so we decided to give 3rd party solution a try. These are my candidates but I don't have time to really try them all: DeviceAtlas - 1 year personal evaluation, but basic license is affordable. Their database look solid with daily update and user-contributed tests / updates. I am favoring this one at the moment. DetectRight - I was recommended this by a colleague but really can't find much from their site. 20k devices -- really? WURFL - Open source, database collaboratively derived from UAProf. So basically if you're going with UAProf solution, you're better off with WURFL. DetectMoBileBrowsers - This looks like the simplest of all. Too bad it's language dependent (PHP). Please share your experience or suggestions!

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• Turn-based Client-Server Card Game - Unicast (TCP) or Multicast (UDP)

  - by LDM91

  I am currently planning to make a card game project where the clients will communicate with the server in a turn-based and synchronous manner using messages sent over sockets. The problem I have is how to handle the following scenario: (Client takes it turn and sends its action to server) Client sends a message telling the server its move for the turn (e.g. plays the card 5 from its hand which needs to placed onto the table) Server receives messages and updates game state (server will hold all game state). Server iterates through a list of connected clients and sends a message to tell of them change in state Clients all refresh to display the state This is all based on using TCP, and looking at it now it seems a bit like the Observer pattern. The reason this seems to be an issue to me is this message doesn't seem to be point-to-point like the others as I want to send it to all the clients, and doesn't seem very efficient sending the same message in that way. I was thinking about using multicasting with UDP as then I could send the message to all the clients, however wouldn't this mean that the clients would in theory be able to message each other? There is of course the synchronous aspect as well, though this could be put on top of the UDP I guess. Basically, I would like to know what would be good practice as this project is really all about learning, and even though it won't be big enough to encounter performance issues from this I would like to consider them anyway. However, please note I am not interested in using message oriented middleware as a solution (I have experience with using MOM and I'm interested in considering other options excluding MOM if TCP sockets is a bad idea!).

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• Can Clojure's thread-based agents handle c10k performance?

  - by elliot42

  I'm writing a c10k-style service and am trying to evaluate Clojure's performance. Can Clojure agents handle this scale of concurrency with its thread-based agents? Other high performance systems seem to be moving towards async-IO/events/greenlets, albeit at a seemingly higher complexity cost. Suppose there are 10,000 clients connected, sending messages that should be appended to 1,000 local files--the Clojure service is trying to write to as many files in parallel as it can, while not letting any two separate requests mangle the same single file by writing at the same time. Clojure agents are extremely elegant conceptually--they would allow separate files to be written independently and asynchronously, while serializing (in the database sense) multiple requests to write to the same file. My understanding is that agents work by starting a thread for each operation (assume we are IO-bound and using send-off)--so in this case is it correct that it would start 1,000+ threads? Can current-day systems handle this number of threads efficiently? Most of them should be IO-bound and sleeping most of the time, but I presume there would still be a context-switching penalty that is theoretically higher than async-IO/event-based systems (e.g. Erlang, Go, node.js). If the Clojure solution can handle the performance, it seems like the most elegant thing to code. However if it can't handle the performance then something like Erlang or Go's lightweight processes might be preferable, since they are designed to have tens of thousands of them spawned at once, and are only moderately more complex to implement. Has anyone approached this problem in Clojure or compared to these other platforms? (Thanks for your thoughts!)

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• How to show or direct a business analyst to do data modelling?

  - by AaronLS

  Our business analysts pushed hard to collect data through a spreadsheet. I am the programmer responsible for importing that data. Usually when they push hard for something like this, I never know how well it will work out until a few weeks later when I have time assigned to work on the task of programming the import of the data. I have tried to do as much as possible along the way, named ranges, data validations, etc. But I usually don't have time to take a detailed look at all the data and compare to the destination in the database to determine how well it matches up. A lot of times there will be maybe a little table of items that somehow I have to relate to something else in the database, but there are not natural or business keys present that would allow me to do so. Make the best of this, trying to write something that can compare strings and make a best guess at it and then go through the effort of creating interfaces for a user to match the imported data to the destination. I feel like if the business analyst was actually creating a data model, they would be forced to think about these relationships, and have an appreciation for the need of natural or business keys to be part of the spreadsheet for the purposes of smoothly importing the data. The closest they come to business analysis is a big flat list of fields, and that would be fine if it were like any other data dictionary and include data types+relationships, but it isn't. They are just a bunch of names. No indication of what type of data they might hold, and it is up to me to guess. When I have pushed for more detail, they say that it is just busy work. How can I explain the importance of data modelling? How can I tell them what it is and how to do it? It feels impossible, because they don't have an appreciation for its importance. They do however, usually have an interest in helping out in whatever way they can, it's just this in particular has never gotten a motivated response.

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• Modelling work-flow plus interaction with a database - quick and accessible options

  - by cjmUK

  I'm wanting to model a (proposed) manufacturing line, with specific emphasis on interaction with a traceability database. That is, various process engineers have already mapped the manufacturing process - I'm only interested in the various stations along the line that have to talk to the DB. The intended audience is a mixture of project managers, engineers and IT people - the purpose is to identify: points at which the line interacts with the DB (perhaps going so far as indicating the Store Procs called at each point, perhaps even which parameters are passed.) the communication source (PC/Handheld device/PLC) the communication medium (wireless/fibre/copper) control flow (if leak test fails, unit is diverted to repair station) Basically, the model will be used as a focus different groups on outstanding tasks; for example, I'm interested in the DB and any front-end app needed, process engineers need to be thinking about the workflow and liaising with the PLC suppliers, the other IT guys need to make sure we have the hardware and comms in place. Obviously I could just improvise in Visio, but I was wondering if there was a particular modelling technique that might particularly suit my needs or my audience. I'm thinking of a visual model with supporting documentation (as little as possible, as much as is necessary). Clearly, I don't want something that will take me ages to (effectively) learn, nor one that will alienate non-technical members of the project team. So far I've had brief looks at BPMN, EPC Diagrams, standard Flow Diagrams... and I've forgotten most of what I used to know about UML... And I'm not against picking and mixing... as long as it is quick, clear and effective. Conclusion: In the end, I opted for a quasi-workflow/dataflow diagram. I mapped out the parts of the manufacturing process that interact with the traceability DB, and indicated in a significantly-simplified form, the data flows and DB activity. Alongside which, I have a supporting document which outlines each process, the data being transacted for each process (a 'data dictionary' of sorts) and details of hardware and connectivity required. I can't decide whether is a product of genius or a crime against established software development practices, but I do think that is will hit the mark for this particular audience.

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• Analyzing the errorlog

  - by TiborKaraszi

  How often do you do this? Look over each message (type) in the errorlog file and determine whether this is something you want to act on. Sure, some (but not all) of you have some monitoring solution in place, but are you 100% confident that it really will notify for all messages that you might find interesting? That there isn't even one little message hiding in there that you would find valuable knowing about? Or how about messages that you typically don't are about, but knowing that you have a high...(read more)

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• Upgrading from Express Edition to Standard Edition

  - by TiborKaraszi

  Say you encounter an SQL Server which is Express Edition, and it really should have been some higher edition. Sounds familiar? It is common for me as a consultant to find plenty of SQL Servers at a customer's site. Many of the databases in these will be moved (typically using backup and restore) to a "real" SQL Server. But in some cases, this might not be desirable. You want to convert the whole instance, from Express to a "real" SQL Server edition. I'm attending a great SharePoint course for Daniel...(read more)

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• What modelling technique do you use for your continuous design?

  - by d3prok

  Together with my teammates, I'm trying to self-learn XP and apply its principles. We're successfully working in TDD and happily refactoring our code and design. However we're having problems with the overall view of the design of the project. Lately we were wondering what would be the "good" practices for an effective continuous design of the code. We're not strictly seeking the right model, like CRC cards, communication diagrams, etc., instead we're looking for a technique to constantly collaborate on the high level view of the system (not too high though). I'll try to explain myself better: I'm actually interested in the way CRC cards are used to brainstorm a model and I would mix them with some very rough UML diagrams (that we already use). However, what we're looking for are some principles for deciding when, how and how much to model during our iterations. Have you any suggestion on this matter? For example, when your teammates and you know you need a design session and how your meetings work?

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• Offset Forward vector of object based on Rotation

  - by Taylor

  I'm using the Bullet 3D physics engine in a iOS application running openGL ES 1.1 Currently I'm accepting info from the gyroscope to allow the user to "look around" a 3d world that follows a bouncing ball (note: it only takes in the yaw to look around 360 degrees). Im also accepting information from the accelerometer based on the tilt to push the ball. As of right now, to move forward, the user tilts the devise forward (using the accelerometer); to move to the right, the user tilts the devise to the right and so on. The forward vector is currently along it's local Z-axis. The problem is that I want to change the ball bounce based on where the user has changed the view. If I change the view, the ball bounces in the fixed direction. I want to change the forward facing direction so that when a user changes the view (say to the look at the right of the world, the user rotates the device), tilting the devise forward will result in a forward force in that direction. Basically, I want the forward vector to take the rotation into consideration. Sorry if I didn't explain the issue well enough, its kind of confusing to write down.

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• Backup and the evil RETAINDAYS option

  - by TiborKaraszi

  "So what bad has this option done?", you probably as yourself. Well, not much, but I find it evil because it confuses people, especially those new to SQL Server. I have many times seen people specifying something like 3, and expect SQL Server to keep the three most recent backups in the backup file and overwrite everything which is older than that. Well, that is not what the option does. But before we go into details, let's look at an example backup command which is using this option: BACKUP DATABASE...(read more)

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• UML Receptions and AcceptEventActions

  - by Silli

  What shall be the relationship between the receptions of a class (was classifier before Aadaam correction) and the AcceptEventActions in the activity describing the behavior of its instances? I understand the former is related to signals reception of the type while the latter is related to runtime ReceiveSignalEvent events of the class instances (objects). But it is not totally clear to me how to express consistency among these constructs.

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• Generating HTML Help files based on XML documentation

  - by geekrutherford

  Since discovering the XML commenting features built into .NET years ago I have been using it to help make my code more readable and simpler for other developers to understand exactly what the code is doing. Entering /// preceding a line of code causes Visual Studio to insert "summary" tags.  It also results in additional tags being generated if you are commenting a method with parameters and a return type. I already knew that Intellisense would pick up these comments and display them when coding and selecting properties, methods, etc. from a class.  I also knew that you could set Visual Studio to generate an XML file containing said comments.  Only recently did I begin to wonder if I could generate some kind of readable help files based on these comments I so diligently added. After searching the web I came across NDoc, an open source project which creates documentation for you based on the XML files generated by Visual Studio.  Unfortunately, NDoc has become stale and no longer supported (last release was back in 2005). Fortunately there is a little known tool from Microsoft themselves called "Sandcastle Help File Builder".  This nifty little tool gives you a graphical interface that allows you to specify multiple DLL and XML files from which to generate a MSDN like HTML Help File for your own projects! You can check it out here: http://shfb.codeplex.com/ If you are curious how to set Visual Studio to generate the above reference XML documentation files simply go to your projects property page and edit as shown below (my paths are specific, you can leave yours at the default values):

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• Advice on reconciling discordant data

  - by Justin

  Let me support my question with a quick scenario. We're writing an app for family meal planning. We'll produce daily plans with a target calorie goal and meals to achieve it for our nuclear family. Our calorie goal will be calculated for each person from their attributes (gender, age, weight, activity level). The weight attribute is the simplest example here. When Dad (the fascist nerd who is inflicting this on his family) first uses the application he throws approximate values into it for Daughter. He thinks she is 5'2" (157 cm) and 125 lbs (56kg). The next day Mom sits down to generate the menu and looks back over what the bumbling Dad did, quietly fumes that he can never recall anything about the family, and says the value is really 118 lbs! This is the first introduction of the discord. It seems, in this scenario, Mom is probably more correct that Dad. Though both are only an approximation of the actual value. The next day the dear Daughter decides to use the program and sees her weight listed. With the vanity only a teenager could muster she changes the weight to 110 lbs. Later that day the Mom returns home from a doctor's visit the Daughter needed and decides that it would be a good idea to update her Daughter's weight in the program. Hooray, another value, this time 117 lbs. Now how do you reconcile these data points? Measurement error, confidence in parties, bias, and more all confound the data. In some idealized world we'd have a weight authority of some nature providing the one and only truth. How about in our world though? And the icing on the cake is that this single data point changes over time. How have you guys solved or managed this conflict?

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• How do you handle domain logic that spans multiple model objects in an ORM?

  - by duality_

  So I know that business logic should be placed in the model. But using an ORM it is not as clear where I should place code that handles multiple objects. E.g. let's say we have a Customer model which has a type of either sporty or posh and we wanted to customer.add_bonus() to every posh customer. Where would we do this? Do we create a new class to handle all this? If yes, where do we put it (alongside all the other model classes, but not subclass it from the ORM?)? I'm currently using django framework in python, so specific suggestions are even more wanted.

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• How would you model an objects representing different phases of an entity life cycle?

  - by Ophir Yoktan

  I believe the scenario is common mostly in business workflows - for example: loan management the process starts with a loan application, then there's the loan offer, the 'live' loan, and maybe also finished loans. all these objects are related, and share many fields all these objects have also many fields that are unique for each entity the variety of objects maybe large, and the transformation between the may not be linear (for example: a single loan application may end up as several loans of different types) How would you model this? some options: an entity for each type, each containing the relevant fields (possibly grouping related fields as sub entities) - leads to duplication of data. an entity for each object, but instead of duplicating data, each object has a reference to it's predecessor (the loan doesn't contain the loaner details, but a reference to the loan application) - this causes coupling between the object structure, and the way it was created. if we change the loan application, it shouldn't effect the structure of the loan entity. one large entity, with fields for the whole life cycle - this can create 'mega objects' with many fields. it also doesn't work well when there's a one to many or many to many relation between the phases.

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• Two bugs you should be aware of

  - by AaronBertrand

  In the past 24 hours I have come across two bugs that can be quite problematic in certain environments. LPIM issue with SetFileIoOverlappedRange Last night the CSS team posted a blog entry detailing a potential issue with Lock Pages in Memory and Windows' SetFileIoOverlappedRange API. I tweeted about it at the time, but thought it could use a little more treatment. The potential symptoms can vary, but include the following (as quoted from the blog post): Wide ranging in SQL from invalid write location,...(read more)

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• Help w/ iPad 1 performance for tile-based DOM Javascript game

  - by butr0s

  I've made a 2D tile-based game with DOM/Javascript. For each level, the map data is loaded and parsed, then lots of tiles ( elements) are drawn onto a larger "map" element. The map is inside of a container that hides overflow, so I can move the map element around by positioning it absolutely. Works a treat on desktop browsers, and my iPad 2. My problem is that performance is really bad on iPad 1. The performance hit is directly related to all the tile elements in my map, because when I remove or reduce the number of tiles drawn, performance improves. Optimizing my collision detection loop has no effect. My first thought was to batch groups of tiles into containers, then hide/show them based on proximity to the player, however this still causes a huge hiccup when the player moves and a new group of tiles is displayed (offscreen). Actually removing the out-of-sight elements from the DOM, then re-adding them as necessary is no faster. Anyone know of any tips that might speed up DOM performance here? My map is 1920 x 1920 pixels, so as far as I know should be within the WebKit texture limit on iOS 5/iPad. The map is being moved with CSS3 transforms, and I've picked all the other obvious low-hanging fruit.

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• Location-Based redirection and duplication in sub-directories affecting SEO

  - by Joshua

  I currently own the website www.xyz.com. The website has a sub-directory for each of the 3 target countries: .../en-US/ (United States), .../es-MX/ (Mexico), and .../es-DO/ (Dominican Republic). I have two main questions about this setup: Currently, the main domain/root (xyz.com) contains a blank index.php file, but I would like for a user to be redirected to one of the sub-directories based on their regional location. What is the best way to accomplish this? I have looked at using browser language-based redirection, but how would I know whether to direct a user to the MX or DO site if the browser language is set to spanish? Is there a way to detect a user's geographic location? Also, the 3 websites are practically identical except they all have 3 unique color schemes and the US site is in english while the MX and DO sites are in spanish. My problem is that I believe GoogleBot is penalizing/banning my site because the spanish text on the MX and DO pages are nearly identical and are thus marked as duplicates/spam. Is there a way to avoid this?

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• Testing my model for hybrid scheduling in Embedded Systems

  - by markusian

  I am working on a project for school, where I have to analyze the performances of a few fixed-priority servers algorithms (polling server, deferrable server, priority exchange) using a simulator in the case of hybrid scheduling, where we have both hard periodic tasks and soft aperiodic tasks. In my model I consider that: the hard tasks have a period equal to their deadline, with a known worst case execution time (wcet). The actual execution time could be smaller than the wcet. the soft tasks have a known wcet and random interarrival times. The actual execution time could be smaller than the wcet. In order to test those algorithms I need realistic case studies. For this reason I'm digging in the scientific literature but I am facing different problems: Sometimes I find a list of hard tasks with wcet, but it is not specified how the soft tasks parameters are found. Given the wcet of a task, how can I model its actual execution time? This means, what random distribution should I use considering the wcet? How can I model the random interarrival times of soft aperiodic tasks?

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• Role based access to resources for a RESTful service

  - by mutex

  I'm still wrapping my head around REST, but I wonder if someone can help with any suggestions or approaches to role based access control for a RESTful service, particularly from the point of view of securing the data and how the URLs might look. It's probably best to consider an example: Say I have a REST service for Customers, and want to split the users of this REST service into Admin, Editor and Reader roles: Admins can change all attributes of a Customer resource Editors can change only some Readers can only view them. Access control rights are assigned to the Customers entities individually. So for example a user of the service might have admin rights to Customers 1,2 and 3 but Editor access to 4,5 and Reader access to 7,8,9. Now consider the user calling the service. What is a good way to seperate the list of Customers for the current User? GET /Customer - this might get a list of all customers that the current user has Admin\Editor\Reader access to. But then on each Customer the consumer would need an indication of what role they have. Or would it be "better" having something like GET /Customer/Admin - return all customers the current user has Admin access to. Just looking for some high level pointers or reading on a decent way to secure\filter the resources based on roles of the current user.

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• Wait random number of minutes

  - by TiborKaraszi

  Why on earth would you want to do that? you ask. Say you have a job that is scheduled to start at the same time over a number of servers. This might be because you have an SQL Server Master/Target server environment (MSX/TSX) or you quite simply script a job and execute that script on several servers. You probably want to spread the load on your SAN and virtual machine host a bit. This is the exact reason I use this procedure. I frequently use MSX servers and I usually add a job step (executing this...(read more)

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• Matching users based on a series of questions

  - by SeanWM

  I'm trying to figure out a way to match users based on specific personality traits. Each trait will have its own category. I figure in my user table I'll add a column for each category: id name cat1 cat2 cat3 1 Sean ? ? ? 2 Other ? ? ? Let's say I ask each user 3 questions in each category. For each question, you can answer one of the following: No, Maybe, Yes How would I calculate one number based off the answers in those 3 questions that would hold a value I can compare other users to? I was thinking having some sort of weight. Like: No -> 0 Maybe -> 1 Yes -> 2 Then doing some sort of meaningful calculation. I want to end up with something like this so I can query the users and find who matches close: id name cat1 cat2 cat3 1 Sean 4 5 1 2 Other 1 2 5 In the situation above, the users don't really match. I'd want to match with someone with a +1 or -1 of my score in each category. I'm not a math guy so I'm just looking for some ideas to get me started.

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