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  • Are there design patterns or generalised approaches for particle simulations?

    - by romeovs
    I'm working on a project (for college) in C++. The goal is to write a program that can more or less simulate a beam of particles flying trough the LHC synchrotron. Not wanting to rush into things, me and my team are thinking about how to implement this and I was wondering if there are general design patterns that are used to solve this kind of problem. The general approach we came up with so far is the following: there is a World that holds all objects you can add objects to this world such as Particle, Dipole and Quadrupole time is cut up into discrete steps, and at each point in time, for each Particle the magnetic and electric forces that each object in the World generates are calculated and summed up (luckily electro-magnetism is linear). each Particle moves accordingly (using a simple estimation approach to solve the differential movement equations) save the Particle positions repeat This seems a good approach but, for instance, it is hard to take into account symmetries that might be present (such as the magnetic field of each Quadrupole) and is this thus suboptimal. To take into account such symmetries as that of the Quadrupole field, it would be much easier to (also) make space discrete and somehow store form of the Quadrupole field somewhere. (Since 2532 or so Quadrupoles are stored this should lead to a massive gain of performance, not having to recalculate each Quadrupole field) So, are there any design patterns? Is the World-approach feasible or is it old-fashioned, bad programming? What about symmetry, how is that generally taken into acount?

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  • Are Java's public fields just a tragic historical design flaw at this point?

    - by Avi Flax
    It seems to be Java orthodoxy at this point that one should basically never use public fields for object state. (I don't necessarily agree, but that's not relevant to my question.) Given that, would it be right to say that from where we are today, it's clear that Java's public fields were a mistake/flaw of the language design? Or is there a rational argument that they're a useful and important part of the language, even today? Thanks! Update: I know about the more elegant approaches, such as in C#, Python, Groovy, etc. I'm not directly looking for those examples. I'm really just wondering if there's still someone deep in a bunker, muttering about how wonderful public fields really are, and how the masses are all just sheep, etc. Update 2: Clearly static final public fields are the standard way to create public constants. I was referring more to using public fields for object state (even immutable state). I'm thinking that it does seem like a design flaw that one should use public fields for constants, but not for state… a language's rules should be enforced naturally, by syntax, not by guidelines.

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  • Interface (contract), Generics (universality), and extension methods (ease of use). Is it a right design?

    - by Saeed Neamati
    I'm trying to design a simple conversion framework based on these requirements: All developers should follow a predefined set of rules to convert from the source entity to the target entity Some overall policies should be able to be applied in a central place, without interference with developers' code Both the creation of converters and usage of converter classes should be easy To solve these problems in C# language, A thought came to my mind. I'm writing it here, though it doesn't compile at all. But let's assume that C# compiles this code: I'll create a generic interface called IConverter public interface IConverter<TSource, TTarget> where TSource : class, new() where TTarget : class, new() { TTarget Convert(TSource source); List<TTarget> Convert(List<TSource> sourceItems); } Developers would implement this interface to create converters. For example: public class PhoneToCommunicationChannelConverter : IConverter<Phone, CommunicationChannle> { public CommunicationChannel Convert(Phone phone) { // conversion logic } public List<CommunicationChannel> Convert(List<Phone> phones) { // conversion logic } } And to make the usage of this conversion class easier, imagine that we add static and this keywords to methods to turn them into Extension Methods, and use them this way: List<Phone> phones = GetPhones(); List<CommunicationChannel> channels = phones.Convert(); However, this doesn't even compile. With those requirements, I can think of some other designs, but they each lack an aspect. Either the implementation would become more difficult or chaotic and out of control, or the usage would become truly hard. Is this design right at all? What alternatives I might have to achieve those requirements?

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  • Abstracting functionality

    - by Ralf Westphal
    Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/08/22/abstracting-functionality.aspxWhat is more important than data? Functionality. Yes, I strongly believe we should switch to a functionality over data mindset in programming. Or actually switch back to it. Focus on functionality Functionality once was at the core of software development. Back when algorithms were the first thing you heard about in CS classes. Sure, data structures, too, were important - but always from the point of view of algorithms. (Niklaus Wirth gave one of his books the title “Algorithms + Data Structures” instead of “Data Structures + Algorithms” for a reason.) The reason for the focus on functionality? Firstly, because software was and is about doing stuff. Secondly because sufficient performance was hard to achieve, and only thirdly memory efficiency. But then hardware became more powerful. That gave rise to a new mindset: object orientation. And with it functionality was devalued. Data took over its place as the most important aspect. Now discussions revolved around structures motivated by data relationships. (John Beidler gave his book the title “Data Structures and Algorithms: An Object Oriented Approach” instead of the other way around for a reason.) Sure, this data could be embellished with functionality. But nevertheless functionality was second. When you look at (domain) object models what you mostly find is (domain) data object models. The common object oriented approach is: data aka structure over functionality. This is true even for the most modern modeling approaches like Domain Driven Design. Look at the literature and what you find is recommendations on how to get data structures right: aggregates, entities, value objects. I´m not saying this is what object orientation was invented for. But I´m saying that´s what I happen to see across many teams now some 25 years after object orientation became mainstream through C++, Delphi, and Java. But why should we switch back? Because software development cannot become truly agile with a data focus. The reason for that lies in what customers need first: functionality, behavior, operations. To be clear, that´s not why software is built. The purpose of software is to be more efficient than the alternative. Money mainly is spent to get a certain level of quality (e.g. performance, scalability, security etc.). But without functionality being present, there is nothing to work on the quality of. What customers want is functionality of a certain quality. ASAP. And tomorrow new functionality needs to be added, existing functionality needs to be changed, and quality needs to be increased. No customer ever wanted data or structures. Of course data should be processed. Data is there, data gets generated, transformed, stored. But how the data is structured for this to happen efficiently is of no concern to the customer. Ask a customer (or user) whether she likes the data structured this way or that way. She´ll say, “I don´t care.” But ask a customer (or user) whether he likes the functionality and its quality this way or that way. He´ll say, “I like it” (or “I don´t like it”). Build software incrementally From this very natural focus of customers and users on functionality and its quality follows we should develop software incrementally. That´s what Agility is about. Deliver small increments quickly and often to get frequent feedback. That way less waste is produced, and learning can take place much easier (on the side of the customer as well as on the side of developers). An increment is some added functionality or quality of functionality.[1] So as it turns out, Agility is about functionality over whatever. But software developers’ thinking is still stuck in the object oriented mindset of whatever over functionality. Bummer. I guess that (at least partly) explains why Agility always hits a glass ceiling in projects. It´s a clash of mindsets, of cultures. Driving software development by demanding small increases in functionality runs against thinking about software as growing (data) structures sprinkled with functionality. (Excuse me, if this sounds a bit broad-brush. But you get my point.) The need for abstraction In the end there need to be data structures. Of course. Small and large ones. The phrase functionality over data does not deny that. It´s not functionality instead of data or something. It´s just over, i.e. functionality should be thought of first. It´s a tad more important. It´s what the customer wants. That´s why we need a way to design functionality. Small and large. We need to be able to think about functionality before implementing it. We need to be able to reason about it among team members. We need to be able to communicate our mental models of functionality not just by speaking about them, but also on paper. Otherwise reasoning about it does not scale. We learned thinking about functionality in the small using flow charts, Nassi-Shneiderman diagrams, pseudo code, or UML sequence diagrams. That´s nice and well. But it does not scale. You can use these tools to describe manageable algorithms. But it does not work for the functionality triggered by pressing the “1-Click Order” on an amazon product page for example. There are several reasons for that, I´d say. Firstly, the level of abstraction over code is negligible. It´s essentially non-existent. Drawing a flow chart or writing pseudo code or writing actual code is very, very much alike. All these tools are about control flow like code is.[2] In addition all tools are computationally complete. They are about logic which is expressions and especially control statements. Whatever you code in Java you can fully (!) describe using a flow chart. And then there is no data. They are about control flow and leave out the data altogether. Thus data mostly is assumed to be global. That´s shooting yourself in the foot, as I hope you agree. Even if it´s functionality over data that does not mean “don´t think about data”. Right to the contrary! Functionality only makes sense with regard to data. So data needs to be in the picture right from the start - but it must not dominate the thinking. The above tools fail on this. Bottom line: So far we´re unable to reason in a scalable and abstract manner about functionality. That´s why programmers are so driven to start coding once they are presented with a problem. Programming languages are the only tool they´ve learned to use to reason about functional solutions. Or, well, there might be exceptions. Mathematical notation and SQL may have come to your mind already. Indeed they are tools on a higher level of abstraction than flow charts etc. That´s because they are declarative and not computationally complete. They leave out details - in order to deliver higher efficiency in devising overall solutions. We can easily reason about functionality using mathematics and SQL. That´s great. Except for that they are domain specific languages. They are not general purpose. (And they don´t scale either, I´d say.) Bummer. So to be more precise we need a scalable general purpose tool on a higher than code level of abstraction not neglecting data. Enter: Flow Design. Abstracting functionality using data flows I believe the solution to the problem of abstracting functionality lies in switching from control flow to data flow. Data flow very naturally is not about logic details anymore. There are no expressions and no control statements anymore. There are not even statements anymore. Data flow is declarative by nature. With data flow we get rid of all the limiting traits of former approaches to modeling functionality. In addition, nomen est omen, data flows include data in the functionality picture. With data flows, data is visibly flowing from processing step to processing step. Control is not flowing. Control is wherever it´s needed to process data coming in. That´s a crucial difference and needs some rewiring in your head to be fully appreciated.[2] Since data flows are declarative they are not the right tool to describe algorithms, though, I´d say. With them you don´t design functionality on a low level. During design data flow processing steps are black boxes. They get fleshed out during coding. Data flow design thus is more coarse grained than flow chart design. It starts on a higher level of abstraction - but then is not limited. By nesting data flows indefinitely you can design functionality of any size, without losing sight of your data. Data flows scale very well during design. They can be used on any level of granularity. And they can easily be depicted. Communicating designs using data flows is easy and scales well, too. The result of functional design using data flows is not algorithms (too low level), but processes. Think of data flows as descriptions of industrial production lines. Data as material runs through a number of processing steps to be analyzed, enhances, transformed. On the top level of a data flow design might be just one processing step, e.g. “execute 1-click order”. But below that are arbitrary levels of flows with smaller and smaller steps. That´s not layering as in “layered architecture”, though. Rather it´s a stratified design à la Abelson/Sussman. Refining data flows is not your grandpa´s functional decomposition. That was rooted in control flows. Refining data flows does not suffer from the limits of functional decomposition against which object orientation was supposed to be an antidote. Summary I´ve been working exclusively with data flows for functional design for the past 4 years. It has changed my life as a programmer. What once was difficult is now easy. And, no, I´m not using Clojure or F#. And I´m not a async/parallel execution buff. Designing the functionality of increments using data flows works great with teams. It produces design documentation which can easily be translated into code - in which then the smallest data flow processing steps have to be fleshed out - which is comparatively easy. Using a systematic translation approach code can mirror the data flow design. That way later on the design can easily be reproduced from the code if need be. And finally, data flow designs play well with object orientation. They are a great starting point for class design. But that´s a story for another day. To me data flow design simply is one of the missing links of systematic lightweight software design. There are also other artifacts software development can produce to get feedback, e.g. process descriptions, test cases. But customers can be delighted more easily with code based increments in functionality. ? No, I´m not talking about the endless possibilities this opens for parallel processing. Data flows are useful independently of multi-core processors and Actor-based designs. That´s my whole point here. Data flows are good for reasoning and evolvability. So forget about any special frameworks you might need to reap benefits from data flows. None are necessary. Translating data flow designs even into plain of Java is possible. ?

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  • Design for a machine learning artificial intelligence framework

    - by Lirik
    This is a community wiki which aims to provide a good design for a machine learning/artificial intelligence framework (ML/AI framework). Please contribute to the design of a language-agnostic framework which would allow multiple ML/AI algorithms to be plugged into a single framework which: runs the algorithms with a user-specified data set. facilitates learning, qualification, and classification. allows users to easily plug in new algorithms. can aggregate or create an ensemble of the existing algorithms. can save/load the progress of the algorithm (i.e. save the network and weights of a neural network, save the tree of a decision tree, etc.). What is a good design for this sort of ML/AI framework?

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  • Design for a machine learning artificial intelligence framework (community wiki)

    - by Lirik
    This is a community wiki which aims to provide a good design for a machine learning/artificial intelligence framework (ML/AI framework). Please contribute to the design of a language-agnostic framework which would allow multiple ML/AI algorithms to be plugged into a single framework which: runs the algorithms with a user-specified data set. facilitates learning, qualification, and classification. allows users to easily plug in new algorithms. can aggregate or create an ensemble of the existing algorithms. can save/load the progress of the algorithm (i.e. save the network and weights of a neural network, save the tree of a decision tree, etc.). What is a good design for this sort of ML/AI framework?

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  • NHibernate HiLo generation and SQL 2005/8 Schemas

    - by Kirk Clawson
    I have an issue on my hands that I've spent several days searching for an answer to no avail... We're using HiLo Id generation, and everything seems to be working fine, as long as the entity table is in the same schema as the hibernate_unique_key table. The table structure is pretty simple. I have my hi value table in the db as dbo.hibernate_unique_key. Several entity table are also in the dbo schema, and they work without issue. Then we have tables under the "Contact" schema (such as Contact.Person and Contact.Address). In the Person Mapping file: <class name="Person" table="Person" schema="Contact"> <id name="Id" unsaved-value="0"> <generator class="hilo"> <param name="max_lo">100</param> </generator> </id> ... When I try to insert a Person entity, I get an error of "Invalid object name 'Contact.hibernate_unique_key'. That error is certainly clear enough. So I add: <param name="schema">dbo</param> to my mapping file/generator element. Now, when the SessionFactory is built, I get a "An item with the same key has already been added." error. So now I'm a bit stuck. I can't leave the HiLo generator without a schema, because it picks up the schema from the Class, and I can't specify the schema because it's already been added (presumably because it's my "default_schema" as identified in my XML cfg file). Am I completely hosed here? Must I either A) Keep all my tables in the dbo schema or B) Create a separate HiLo Key table for each unique schema in the DB? Neither of those scenarios is particularly palatable for my application, so I'm hoping that I can "fix" my mapping files to address this issue.

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  • Winforms Which Design Pattern / Agile Methodology to choose

    - by ZedBee
    I have developed desktop (winforms) applications without following any proper design pattern or agile methodologies. Now I have been given the task to re-write an existing ERP application in C# (Winforms). I have been reading about Domain Driven Design, scrum, extreme programming, layered architecture etc. Its quite confusing and really hard (because of time limitations) to go and try each and every method and then deciding which way to go. Its very hard for me to understand the bigger picture and see which pattern and agile methodology to follow. To be more specific about what I want to know is that: Is it possible to follow Domain Driven Design and still be agile. Should I choose Extreme programming or scrum in this specific scenario Where does MVP and MVVM fits, which one would be a better option for me

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  • What design patterns are used in diagramming tools?

    - by TheMachineCharmer
    Diagram.net is good diagramming tool. I need to understand what design patterns are used by this tool so that I can understand how it works. What design patterns are used in this tool? What design patterns are generally used for diagramming tools? I would also like to know how can I use this to develop very simple diagramming tool (Only rectangular nodes and straight links). NOTE/Caution: I am doing this for FUN so please don't direct me to existing tools(I might down vote.. just kiddin ;).

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  • android call log like design

    - by Alxandr
    I'm trying to create a design for a list that looks like (and mostly behaves like) the call log, like shown here: I don't need all the design, but what I'm trying to achieve is the two-columned design with the splitter in-between, and the behavior that if I click on the main item (the left part) one thing happens (in this case, you open some details about the call), and if you press the outer right part something else happens (you call the contact). I'm pretty new to android, but I've managed to do most of the designs I wanted so far, so I don't need the entire layout for this one, only the part that does the splitting and the splitter. And if possible it would be nice to know how to map the clicks appropriately, though I think I might be able to find that out by my self.

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  • View centric design with Django

    - by wishi_
    Hi! I'm relatively new to Django and I'm designing a website that primarily needs usability experience, speaking of optimized CSS, HTML5 and UI stuff. It's very easy to use Django for data/Model centric design. Just designing a couple of Python classes and ./manage.py syncdb - there's your Model. But I'm dealing with a significant amount of View centric challenges. (Different user classes, different tasks, different design challenges.) The official Django tutorial cursorily goes through using a "Template". Is there any Design centric guide for Django, or a set of Templates that are ready and useable? I don't want to start from scratch using JS, HTML5, Ajax and everything. From the Model layer perspective Django is very rapid and delivering a working base system. I wonder whether there's something like that for the Views.

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  • Alternative design for a synonyms table?

    - by Majid
    I am working on an app which is to suggest alternative words/phrases for input text. I have doubts about what might be a good design for the synonyms table. Design considerations: number of synonyms is variable, i.e. football has one synonym (soccer), but in particular has two (particularly, specifically) if football is a synonym to soccer, the relation exists in the opposite direction as well. our goal is to query a word and find its synonyms we want to keep the table small and make adding new words easy What comes to my mind is a two column design with col a = word and col b = delimited list of synonyms Is there any better alternative? What about using two tables, one for words and the other for relations?

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  • Proper design a Model-Controller in Cocoa?

    - by legege
    Hi, I'm trying to design a simple Cocoa application and I would like to have a clear and easy to understand software architecture. Of course, I'm using a basic MVC design and my question concerns the Model layer. For my application, the Model represents data fetched on the Internet with a XML-RPC API. I'm planning to use Core Data to represent a locally fetched version. How should the data be loaded initially? I'm reading the Cocoa Design Pattern book, and they talk about a Model-Controller that is centric to the Model. How would that be done? Thanks!

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  • Design pattern for mouse interaction

    - by mike
    I need some opinions on what is the "ideal" design pattern for a general mouse interaction. Here the simplified problem. I have a small 3d program (QT and openGL) and I use the mouse for interaction. Every interaction is normally not only a single function call, it is mostly performed by up to 3 function calls (initiate, perform, finalize). For example, camera rotation: here the initial function call will deliver the current first mouse position, whereas the performing function calls will update the camera etc. However, for only a couple of interactions, hardcoding these (inside MousePressEvent, MouseReleaseEvent MouseMoveEvent or MouseWheelEvent etc) is not a big deal, but if I think about a more advanced program (e.g 20 or more interactions) then a proper design is needed. Therefore, how would you design such a interactions inside QT. I hope I made my problem clear enough, otherwise don't bother complain :-) Thanks

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  • Good workflow for website design

    - by Olav
    I would like some idea about a good workflow for Website Design, with a high degree of "offshoring" (Elance, Odesk etc.). I would to do as much as possible "pre production", with client input, ideas etc. stored in IA diagrams, wireframe mockups etc. in something like a Wiki. Also a like the idea about having different people come up with different design proposals. Wouldlike to have some ideas of costs of different phases and tasks ($, %, hours). With Design I mean roughly the aspects of a site that can be done with client-side tools, especially XHTML and CSS. What other tools should I use than IA diagrams.

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  • What is the differnce between an Oracle and Microsoft schema?

    - by Tarzan
    I am working on an enterprise project. Some of the team has an Oracle background and some has a Microsoft SQL Server background. There is much confusion when we talk about schemas. I am trying to provide some clarity. Is this an accurate way to describe the difference in the meaning of schemas between the two technologies? An Oracle schema is associated with a single user and consists of the objects owned by the user. A MS SQL Server schema schema is a namespace.

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  • Good Design for Initialization of Static Array

    - by jplot
    I have a question regarding good design in C++. I have a class A, and all objects of this class use an integer array of constant values (they should share the same array, as their values are constant). The array needs to be computed (just once) before any object A. I thought about having another class B which contains the integer array as a static member, an init() method which would fill this array according to some formula and a static boolean flag initialized (if this variable if true then the init() method would do nothing), but I'm not sure this is the best way to solve my design issue. So my question is, what would be a good design/way to accomplish this ? Thanks in advance.

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  • Help a CRUD programmer think about an "approval workflow"

    - by gerdemb
    I've been working on a web application that is basically a CRUD application (Create, Read, Update, Delete). Recently, I've started working on what I'm calling an "approval workflow". Basically, a request is generated for a material and then sent for approval to a manager. Depending on what is requested, different people need to approve the request or perhaps send it back to the requester for modification. The approvers need to keep track of what to approve what has been approved and the requesters need to see the status of their requests. As a "CRUD" developer, I'm having a hard-time wrapping my head around how to design this. What database tables should I have? How do I keep track of the state of the request? How should I notify users of actions that have happened to their requests? Is their a design pattern that could help me with this? Should I be drawing state-machines in my code? I think this is a generic programing question, but if it makes any difference I'm using Django with MySQL.

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  • many-to-many-to-many, incl alignment of data from diff sources

    - by JefeCoon
    Re-factoring dbase to support many:many:many. At the second and third levels we need to preserve end-user 'mapping' or aligning of data from different sources, e.g. Order 17 FirstpartyOrderID => aha LineItem_for_BigShinyThingy => AA-1 # maps to 77-a LineItem_for_BigShinyThingy => AA-2 # maps to 77-b, 77-c LineItem_for_LittleWidget => AA-x # maps to 77-zulu, 77-alpha, 99-foxtrot LineItem_for_LittleWidget => AA-y # maps to 77-zulu, 99-foxtrot LineItem_for_LittleWidget => AA-z # maps to 77-alpha ThirdpartyOrderID => foo LineItem_for_BigShinyThingy => 77-a LineItem_for_BigShinyThingy => 77-b LineItem_for_BigShinyThingy => 77-c LineItem_for_LittleWidget => 77-zulu LineItem_for_LittleWidget => 77-alpha ThirdpartyOrderID => bar LineItem_for_LittleWidget => 99-foxtrot Each LineItem has daily datapoints reported from its own source (Firstparty|Thirdparty). In our UI & app we provide tools to align these, then we'd like to save them into the cleanest possible schema for querying, enabling us to diff the reported daily datapoints, and perform other daily calculations (which we'll store in the dbase also, fortunately that should be cake once we've nailed this). We need to map related [firstparty|thirdparty]line_items which have their own respective datapoints. We'll be using the association to pull each line_items collection of datapoints for summary and discrepancy calculations. I'm considering two options, std has_many,through x2 --or-- possibly (scary) ubermasterjoin table OptionA: order<<-->> order_join_table[id,order_id,firstparty_order_id,thirdparty_order_id] <<-->>line_item order_join_table[firstparty_order_id]-->raw_order[id] order_join_table[thirdparty_order_id]-->raw_order[id] raw_order-->raw_line_items[raw_order_id] line_item<<-->> line_item_join[id,LI_join_id,firstparty_LI,thirdparty_LI <<-->>raw_line_items line_item_join[firstparty_LI]-->raw_line_item[id] line_item_join[thirdparty_LI]-->raw_line_item[id] raw_line_item<<-->>datapoints = we rely upon join to store all mappings of first|third orders & line_items = keys to raw_* enable lookup of these order & line_item details = concerns about circular references and/or lack of correct mapping logic, e.g order--line_item--raw_line_items vs. order--raw_order--raw_line_items OptionB: order<<-->> join_master[id,order_id,FP_order_id,TP_order_id,FP_line_item_id,TP_line_item_id] join_master[FP_order_id & TP_order_id]-->raw_order[id] join_master[FP_line_item_id & TP_line_item_id]-->raw_line_item[id] = every combo of FP_line_item + TP_line_item writes a record into the join_master table = "theoretically" queries easy/fast/flexible/sexy At long last, my questions: a) any learnings from painful firsthand experience about how best to implement/tune/optimize many-to-many-to-many relationships b) in rails? c) any painful gotchas (circular references, slow queries, spaghetti-monsters) to watch out for? d) any joy & goodness in Rails3 that makes this magically easy & joyful? e) anyone written the "how to do many-to-many-to-many schema in Rails and make it fast & sexy?" tutorial that I somehow haven't found? If not, I'll follow up with our learnings in the hope it's helpful.. Thanks in advance- --Jeff

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  • Worst Web Site Design Ever

    - by Alex Angas
    I'm looking for a very good example of a very poorly designed web site. For example: use of <blink> mixed with many 'cute' animated GIFs (a common home page in the mid-'90s). It needs to display relatively correctly in the popular web browsers of today. Thank you!

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  • How Does EoR Design Work with Multi-tiered Data Center Topology

    - by S.C.
    I just did a ton of reading about the different multi-tier network topology options as outlined by Cisco, and now that I'm looking at the physical options (End of Row (EoR) vs Top of Rack(ToR)), I find myself confused about how these fit into the logical constructs. With ToR it also maps 1:1: at the top of each rack there is a switch(es) that essentially act as the access layer. They connect via fiber to other switches, maybe chassis-based, that act as the aggregation layer, that then connect to the core layer. With EoR it seems that the servers are connecting directly to the aggregation layer, skipping the access layer all together, by plugging directly into what are typically chassis switches. In EoR then is the standard 3-tier model now a 2-tier model: the servers go to the chassis switch which goes straight to the core switch? The reason it matters to me is that my understanding was that the 3-tier model was more desirable due to less complexity. The agg switch pair acts as default gateway and does routing; if you use up all of your ports in your agg layer pair it's much more complicated to add additional switches, than simply adding more switches at the access layer. Are there other downsides to this layout? Does this 3-tier architecture still apply in some way in EoR? Thanks.

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  • design question for transportation agency/workflow system

    - by George2
    I am designing a transportation agency/workflow system, and it including 3 types of people, customer who requests to transport some stuff, drivers who deliver the stuff, and truck manager who manages transport source/destination truck coordination and communicates/organizes drivers. The system is expected to be a web site, and 3 kinds of people could use the web site to submit request, accept request, monitor status of specific stuff transportation, etc. The web site is more like an open agency or a workflow system. I am wondering whether there are any existing technologies, tools or projects (better to be open source, but not a must) which I could build my application faster based on? I prefer to use .Net technologies, but not a must. Thanks in advance!

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  • Database Design - Surrogate keys: Part 1 of many (Rules for Surrogate Keys, E. F. Codd and C J Date

    - by tonyrogerson
    I started writing an article for my blog on surrogate keys drawing in the original research by E F Codd and C J Date, its getting a bit big :) so I'm going to chop it up into a number of posts over the coming weeks depending on my time. I'm interested in your thoughts and if you disagree please let me know but more importantly give me references back to papers stating why you take that position. Hope it makes sense. Surrogate keys There are two factions in the world of Database Design that...(read more)

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