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  • Problems with real-valued input deep belief networks (of RBMs)

    - by Junier
    I am trying to recreate the results reported in Reducing the dimensionality of data with neural networks of autoencoding the olivetti face dataset with an adapted version of the MNIST digits matlab code, but am having some difficulty. It seems that no matter how much tweaking I do on the number of epochs, rates, or momentum the stacked RBMs are entering the fine-tuning stage with a large amount of error and consequently fail to improve much at the fine-tuning stage. I am also experiencing a similar problem on another real-valued dataset. For the first layer I am using a RBM with a smaller learning rate (as described in the paper) and with negdata = poshidstates*vishid' + repmat(visbiases,numcases,1); I'm fairly confident I am following the instructions found in the supporting material but I cannot achieve the correct errors. Is there something I am missing? See the code I'm using for real-valued visible unit RBMs below, and for the whole deep training. The rest of the code can be found here. rbmvislinear.m: epsilonw = 0.001; % Learning rate for weights epsilonvb = 0.001; % Learning rate for biases of visible units epsilonhb = 0.001; % Learning rate for biases of hidden units weightcost = 0.0002; initialmomentum = 0.5; finalmomentum = 0.9; [numcases numdims numbatches]=size(batchdata); if restart ==1, restart=0; epoch=1; % Initializing symmetric weights and biases. vishid = 0.1*randn(numdims, numhid); hidbiases = zeros(1,numhid); visbiases = zeros(1,numdims); poshidprobs = zeros(numcases,numhid); neghidprobs = zeros(numcases,numhid); posprods = zeros(numdims,numhid); negprods = zeros(numdims,numhid); vishidinc = zeros(numdims,numhid); hidbiasinc = zeros(1,numhid); visbiasinc = zeros(1,numdims); sigmainc = zeros(1,numhid); batchposhidprobs=zeros(numcases,numhid,numbatches); end for epoch = epoch:maxepoch, fprintf(1,'epoch %d\r',epoch); errsum=0; for batch = 1:numbatches, if (mod(batch,100)==0) fprintf(1,' %d ',batch); end %%%%%%%%% START POSITIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% data = batchdata(:,:,batch); poshidprobs = 1./(1 + exp(-data*vishid - repmat(hidbiases,numcases,1))); batchposhidprobs(:,:,batch)=poshidprobs; posprods = data' * poshidprobs; poshidact = sum(poshidprobs); posvisact = sum(data); %%%%%%%%% END OF POSITIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% poshidstates = poshidprobs > rand(numcases,numhid); %%%%%%%%% START NEGATIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% negdata = poshidstates*vishid' + repmat(visbiases,numcases,1);% + randn(numcases,numdims) if not using mean neghidprobs = 1./(1 + exp(-negdata*vishid - repmat(hidbiases,numcases,1))); negprods = negdata'*neghidprobs; neghidact = sum(neghidprobs); negvisact = sum(negdata); %%%%%%%%% END OF NEGATIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% err= sum(sum( (data-negdata).^2 )); errsum = err + errsum; if epoch>5, momentum=finalmomentum; else momentum=initialmomentum; end; %%%%%%%%% UPDATE WEIGHTS AND BIASES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% vishidinc = momentum*vishidinc + ... epsilonw*( (posprods-negprods)/numcases - weightcost*vishid); visbiasinc = momentum*visbiasinc + (epsilonvb/numcases)*(posvisact-negvisact); hidbiasinc = momentum*hidbiasinc + (epsilonhb/numcases)*(poshidact-neghidact); vishid = vishid + vishidinc; visbiases = visbiases + visbiasinc; hidbiases = hidbiases + hidbiasinc; %%%%%%%%%%%%%%%% END OF UPDATES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% end fprintf(1, '\nepoch %4i error %f \n', epoch, errsum); end dofacedeepauto.m: clear all close all maxepoch=200; %In the Science paper we use maxepoch=50, but it works just fine. numhid=2000; numpen=1000; numpen2=500; numopen=30; fprintf(1,'Pretraining a deep autoencoder. \n'); fprintf(1,'The Science paper used 50 epochs. This uses %3i \n', maxepoch); load fdata %makeFaceData; [numcases numdims numbatches]=size(batchdata); fprintf(1,'Pretraining Layer 1 with RBM: %d-%d \n',numdims,numhid); restart=1; rbmvislinear; hidrecbiases=hidbiases; save mnistvh vishid hidrecbiases visbiases; maxepoch=50; fprintf(1,'\nPretraining Layer 2 with RBM: %d-%d \n',numhid,numpen); batchdata=batchposhidprobs; numhid=numpen; restart=1; rbm; hidpen=vishid; penrecbiases=hidbiases; hidgenbiases=visbiases; save mnisthp hidpen penrecbiases hidgenbiases; fprintf(1,'\nPretraining Layer 3 with RBM: %d-%d \n',numpen,numpen2); batchdata=batchposhidprobs; numhid=numpen2; restart=1; rbm; hidpen2=vishid; penrecbiases2=hidbiases; hidgenbiases2=visbiases; save mnisthp2 hidpen2 penrecbiases2 hidgenbiases2; fprintf(1,'\nPretraining Layer 4 with RBM: %d-%d \n',numpen2,numopen); batchdata=batchposhidprobs; numhid=numopen; restart=1; rbmhidlinear; hidtop=vishid; toprecbiases=hidbiases; topgenbiases=visbiases; save mnistpo hidtop toprecbiases topgenbiases; backpropface; Thanks for your time

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  • Decoupling into DAL and BLL - my concerns.

    - by novice_man
    Hi, In many posts concerning this topic I come across very simple examples that do not answer my question. Let's say a have a document table and user table. In DAL written in ADO.NET i have a method to retries all documents for some criteria. Now I the UI I have a case where I need to show this list along with the names of the creator. Up to know I have it done with one method in DAL containig JOIN statement. However eveytime I have such a complex method i have to do custom mapping to some object that doesn't mark 1:1 to DB. Should it be put into another layer ? If so then I will have to resing from join query for iteration through results and querying each document author. . . which doen't make sense... (performance) what is the best approach for such scenarios ?

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  • What alternative is there to writing a TCP/IP data relay?

    - by LoudNPossiblyRight
    I am about to write a tcp/ip data relay - application that passes a one way stream of data from one host/port to another host/port. Initially it will be generic, but later on i will customize it to the need of a specific business request. I am guessing that something generic already exists out there so my question is: Has anyone used a third party (preferably open source) data relay in a production environment, if so what is, and do you recommend it? Any platform is fine. Thanks.

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  • Is it a good idea to use MySQL and Neo4j together?

    - by Sanoj
    I will make an application with a lot of similar items (millions), and I would like to store them in a MySQL database, because I would like to do a lot of statistics and search on specific values for specific columns. But at the same time, I will store relations between all the items, that are related in many connected binary-tree-like structures (transitive closure), and relation databases are not good at that kind of structures, so I would like to store all relations in Neo4j which have good performance for this kind of data. My plan is to have all data except the relations in the MySQL database and all relations with item_id stored in the Neo4j database. When I want to lookup a tree, I first search the Neo4j for all the item_id:s in the tree, then I search the MySQL-database for all the specified items in a query that would look like: SELECT * FROM items WHERE item_id = 45 OR item_id = 345435 OR item_id = 343 OR item_id = 78 OR item_id = 4522 OR item_id = 676 OR item_id = 443 OR item_id = 4255 OR item_id = 4345 Is this a good idea, or am I very wrong? I haven't used graph-databases before. Are there any better approaches to my problem? How would the MySQL-query perform in this case?

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  • Of Models / Entities and N-tier applications

    - by Jonn
    I've only discovered a month ago the folly of directly accessing entities / models from the data access layer of an n-tier app. After reading about ViewModels while studying ASP.NET MVC, I've come to understand that to make a truly extensible application the model that the UI layer interacts with must be different from the one that the Data Access layer has access to. But what about the Business layer? Should I have a different set of models for my business layer as well? For true separation of concern, should I have a specific set of models that are relevant only to my business layer so as not to mess around with any entities (possibly generated by for example, the entity framework, or EJB) in the DAL or would that be overkill?

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  • Is it possible to have more than P2P on iPhone with Bluetooth

    - by Ricardo Ferreira
    Hi all, This seems like a straightforward google search answer, but after a while, I still can't be 100% sure of this. I've found Z2Live (http://www.z2live.com/), which is basically a layer above GameKit and they too use only P2P with Bluetooth. So I just want to be sure if I can only have P2P with Bluetooth or if I can have like 4 iPhones all connected to a server (who will also be a client) using Bluetooth. Thanks in advance.

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  • is using private shared objects/variables on class level harmful ?

    - by haansi
    Hello, Thanks for your attention and time. I need your opinion on an basic architectural issue please. In page behind classes I am using a private and shared object and variables (list or just client or simplay int id) to temporary hold data coming from database or class library. This object is used temporarily to catch data and than to return, pass to some function or binding a control. 1st: Can this approach harm any way ? I couldn't analyze it but a thought was using such shared variables may replace data in it when multiple users may be sending request at a time? 2nd: Please comment also on using such variables in BLL (to hold data coming from DAL/database). In this example every time new object of BLL class will be made. Here is sample code: public class ClientManager { Client objclient = new Client(); //Used in 1st and 2nd method List<Client> clientlist = new List<Client>();// used in 3rd and 4th method ClientRepository objclientRep = new ClientRepository(); public List<Client> GetClients() { return clientlist = objclientRep.GetClients(); } public List<Client> SearchClients(string Keyword) { return clientlist = objclientRep.SearchClients(Keyword); } public Client GetaClient(int ClientId) { return objclient = objclientRep.GetaClient(ClientId); } public Client GetClientDetailForConfirmOrder(int UserId) { return objclientRep.GetClientDetailForConfirmOrder(UserId); } } I am really thankful to you for sparing time and paying kind attention.

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  • Dynamically find other hosts in a LAN in Java

    - by Federico Cristina
    A while ago I developed a little LAN chat app. in Java which allows chatting with other hosts, send images, etc. Although it was created just for fun, now it's being used where I work. Currently, there is no "chat server" on the app. where each client registers, updates it's status, etc. (I liked the idea of symmetric design and not depending on a server running on some other machine). Instead, each host is a client/server which has a hosts.properties file with the hostname of the other hosts, and - for instance - broadcasts to each one of them when sending a massive message/image/whatever. In the beginning there were just a couple of hosts, so this hosts.properties file wasn't an issue. But as the amount of users increased, the need of updating that file was a bit daunting. So now I've decided to get rid of it, and each time the app. starts, dynammically find the other active hosts. However, I cannot find the correct way of implement this. I've tried starting different threads, each one of them searching for other hosts in a known range of IP addresses. Something like this (simplified for the sake of readability): /** HostsLocator */ public static void searchForHosts(boolean waitToEnd) { for (int i=0; i < MAX_IP; i+= MAX_IP / threads) { HostsLocator detector = new HostsLocator(i, i+(MAX_IP / threads - 1)); // range: from - to new Thread(detector).start(); } } public void run() { for (int i=from; i<=to; i++) findHosts( maskAddress + Integer.toString(i) ); } public static boolean findHosts(String IP) { InetAddress address = InetAddress.getByName(IP); if ( address.isReachable(CONNECTION_TIME_OUT) ) // host found! } However: With a single thread and a low value in CONNECTION_TIME_OUT (500ms) I get wrong Host Not Found status for for hosts actually active. With a high value in CONNECTION_TIME_OUT (5000ms) and only one single thread takes forever to end With several threads I've also found problems similar like the first one, due to collisions. So... I guess there's a better way of solving this problem but I couldn't find it. Any advice? Thanks!

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  • How to test for secure SMTP mail service on a mail server

    - by Vinay S Shenoy
    I'm working on a project to auto-configure a user's email server settings in Java. I am extracting the mail server from his email address and looking up the MX records of that mail server using the DirContext class with com.sun.jndi.dns.DnsContextFactory. Then I'm opening a Socket to each server and testing them using a HELO command and checking the responses. My problem is that this works only when I test it with the unsecure SMTP port 25. How can I use it with the secure port 465? I tried using Secure Sockets by using SSLSocketFactory sslsocketfactory = (SSLSocketFactory)SSLSocketFactory.getDefault(); SSLSocket socket = (SSLSocket)sslsocketfactory.createSocket(mailserver, STANDARD_SMTP_PORT); But all connections get a timeout exception as follows alt1.gmail-smtp-in.l.google.com. java.net.ConnectException: Operation timed out Please help.

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  • How to write a flexible modular program with good interaction possibilities between modules?

    - by PeterK
    I went through answers on similar topics here on SO but could't find a satisfying answer. Since i know this is a rather large topic, i will try to be more specific. I want to write a program which processes files. The processing is nontrivial, so the best way is to split different phases into standalone modules which then would be used as necessary (since sometimes i will be only interested in the output of module A, sometimes i would need output of five other modules, etc). The thing is, that i need the modules to cooperate, because the output of one might be the input of another. And i need it to be FAST. Moreover i want to avoid doing certain processing more than once (if module A creates some data which then need to be processed by module B and C, i don't want to run module A twice to create the input for modules B,C ). The information the modules need to share would mostly be blocks of binary data and/or offsets into the processed files. The task of the main program would be quite simple - just parse arguments, run required modules (and perhaps give some output, or should this be the task of the modules?). I don't need the modules to be loaded at runtime. It's perfectly fine to have libs with a .h file and recompile the program every time there is a new module or some module is updated. The idea of modules is here mainly because of code readability, maintaining and to be able to have more people working on different modules without the need to have some predefined interface or whatever (on the other hand, some "guidelines" on how to write the modules would be probably required, i know that). We can assume that the file processing is a read-only operation, the original file is not changed. Could someone point me in a good direction on how to do this in C++ ? Any advice is wellcome (links, tutorials, pdf books...).

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  • Is it possible to see computer scheem from programm?

    - by Ole Jak
    So I want to see all the computer scheem like (for ex motherbord, how it is connected to video card) what parts of it are used and how data fluws between them how they are connected where is any thing going wrong or beter than expected. For any computer configuration. Is there any lib or sdk for working with such.. such data?

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  • Platform Framework and Middle-ware

    - by Walidix
    I really want to fix the meanings of this terms.This is what I know about them: Platform: is an environment that allows an application to run and it is usually composite by hardware and software e.g. your machine with your OS installed on it. However some software stack are also called as platform like Java Platform. Framework: is design-oriented. That is, it defines a skeleton of an application type. Also it saves time by offering, through an API, the common functionalities that a kind of applications must implement. Moreover a Framework include a software components that manage the application life-cycle. Middle-ware: is a software that offers services to an application in order to let it inter-operates with other applications or supports different platforms. Middle-ware can be a part of a framework. Is there something wrong or missing ?

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  • Spring MVC: should service layer be returning operation specific DTO's ?

    - by arrages
    In my Spring MVC application I am using DTO in the presentation layer in order to encapsulate the domain model in the service layer. The DTO's are being used as the spring form backing objects. hence my services look something like this: userService.storeUser(NewUserRequestDTO req); The service layer will translate DTO - Domain object and do the rest of the work. Now my problem is that when I want to retrieve a DTO from the service to perform say an Update or Display I can't seem to find a better way to do it then to have multiple methods for the lookup that return different DTO's like... EditUserRequestDTO userService.loadUserForEdit(int id); DisplayUserDTO userService.loadUserForDisplay(int id); but something does not feel right about this approach. The reason do have separate DTO's is that DisplayUserDTO is strongly typed to be read only and also there are many properties of user that are entities from a lookup table in the db (like city and state) so the DisplayUserDTO would have the string description of the properties while the EditUserRequestDTO will have the id's that will back the select drop down lists in the forms. What do you think? thanks

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  • Java plugin framework choice

    - by Marcus
    We're trying to determine how to implement a simple plugin framework for a service we are implementing that allows different types of calculators to be "plugged-in". After reading a number of posts about Java plugin frameworks, it seems like the most common options are: OSGI "Rolling your own" plugin framework The Java Plugin Framework (JPF) The Java Simple Plugin Framework (JSPF) OSGI seems to be more than we need. "Rolling your own" is ok but it would be nice to reuse a common library. So we're down to the JPF and JSPF. JPF seems to not be in active development right now. JSPF seems very simple and really all we need. However I haven't heard much about it. I've only seen one post on StackOverflow about it. Does anyone else have any experience with JSPF? Or any other comments on this design choice? Update: There isn't necessarily a correct answer to this.. however we're going to go with Pavol's idea as we need just a really, really simple solution. Thanks EoH for the nice guide.

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  • How to extend a large website to iPhone app?

    - by xoail
    I am trying to create an iphone app for a large website (as big as amazon.com) and it involves using cookies and what not to get authenticated via the apache intercepter and access the web services exposed by the main website. For that I am looking for strategies to go about developing it. I am new to iphone dev and mostly looking for some architectural guidance. Does anyone know how does apps like ebay and amazon work seamlessly across the website and iphone?

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  • socket timeout and remove O_NONBLOCK option

    - by juxstapose
    Hello, I implemented a socket timeout and retry but in order to do it I had to set the socket as a non-blocking socket. However, I need the socket to block. This was my attempt at a solution to these two problems. This is not working. Subsequent send calls block but never send any data. When I connect without the select and the timeout, subsequent send calls work normally. References: C: socket connection timeout How to reset a socket back to blocking mode (after I set it to nonblocking mode)? Code: fd_set fdset; struct timeval tv; fcntl(dsock, F_SETFL, O_NONBLOCK); tv.tv_sec = theDeviceTimeout; tv.tv_usec = 0; int retries=0; logi(theLogOutput, LOG_INFO, "connecting to device socket num retrys: %i", theDeviceRetry); for(retries=0;retries<theDeviceRetry;retries++) { connect(dsock, (struct sockaddr *)&daddr, sizeof daddr); FD_ZERO(&fdset); FD_SET(dsock, &fdset); if (select(dsock + 1, NULL, &fdset, NULL, &tv) == 1) { int so_error; socklen_t slen = sizeof so_error; getsockopt(dsock, SOL_SOCKET, SO_ERROR, &so_error, &slen); if (so_error == 0) { logi(theLogOutput, LOG_INFO, "connected to socket on port %i on %s", theDevicePort, theDeviceIP); break; } else { logi(theLogOutput, LOG_WARN, "connect to %i failed on ip %s because %s retries %i", theDevicePort, theDeviceIP, strerror(errno), retries); logi(theLogOutput, LOG_WARN, "failed to connect to device %s", strerror(errno)); logi(theLogOutput, LOG_WARN, "error: %i %s", so_error, strerror(so_error)); continue; } } } int opts; opts = fcntl(dsock,F_GETFL); logi(theLogOutput, LOG_DEBUG, "clearing nonblock option %i retries %i", opts, retries); opts ^= O_NONBLOCK; fcntl(dsock, F_SETFL, opts);

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  • Using a Cyc Image in Windows

    - by nrhine1
    Hi, I am trying to use a Microtheory for a research project I am working on, and am having trouble getting my saved Image of constants I create to work correctly. I save the image after creating the constants using (write-image "world\MyImage") and then going to the \server\run\ directory and using run-cyc-32bit.bat -w "world\MyImage" It loads the server correctly, but not with my constants. I found the above command at the reference page here. Thank you for any help

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  • What database strategy to choose for a large web application

    - by Snoopy
    I have to rewrite a large database application, running on 32 servers. The hardware is up to date, each machine has two quad core Xeon and 32 GByte RAM. The database is multi-tenant, each customer has his own file, around 5 to 10 GByte each. I run around 50 databases on this hardware. The app is open to the web, so I have no control on the load. There are no really complex queries, so SQL is not required if there is a better solution. The databases get updated via FTP every day at midnight. The database is read-only. C# is my favourite language and I want to use ASP.NET MVC. I thought about the following options: Use two big SQL servers running SQL Server 2012 to serve the 32 servers with data. On the 32 servers running IIS hosting providing REST services. Denormalize the database and use Redis on each webserver. Use booksleeve as a Redis client. Use a combination of SQL Server and Redis Use SQL Server 2012 together with Hadoop Use Hadoop without SQL Server What is the best way for a read-only database, to get the best performance without loosing maintainability? Does Map-Reduce make sense at all in such a scenario? The reason for the rewrite is, the old app written in C++ with ISAM technology is too slow, the interfaces are old fashioned and not nice to use from an website, especially when using ajax. The app uses a relational datamodel with many tables, but it is possible to write one accerlerator table where all queries can be performed on, and all other information from the other tables are possible by a simple key lookup.

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  • Start with remoting or with WCF

    - by Sheldon
    Hi. I'm just starting with distributed application development. I need to create (all by myself) an enterprise application for document management. That application will run on an intranet (within the firewall, no internet access is required now, BUT is probably that will be later). The application needs to manage images that will be stored within MySQL Server (as blobs) and those images will be then recovered by the app and eventually one or more of them will be converted to PDF. Performance is the most important non-functional requirement. I have a couple of doubts. What do you suggest to use, .NET Remoting or WCF over TCP-IP (I think second one is the best for the moment I need to expose the business logic over internet, changing the protocol). Where do you suggest to make the transformation of the images to pdf files, I'm using iText. (I have thought to have the business logic stored within the IIS and exposed via WCF, and that business logic to be responsible of getting the images and transforming them to PDF, that because the IIS and the MySQL Server are the same physical machine). I ask about where to do the transformation because the app must be accessible from multiple devices, and for example, for mobile devices, the pdf maybe is not necessary. Thank you very much in advance.

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  • Where do objects merge/join data in a 3-tier model?

    - by BerggreenDK
    Its probarbly a simple 3-tier problem. I just want to make sure we use the best practice for this and I am not that familiary with the structures yet. We have the 3 tiers: GUI: ASP.NET for Presentation-layer (first platform) BAL: Business-layer will be handling the logic on a webserver in C#, so we both can use it for webforms/MVC + webservices DAL: LINQ to SQL in the Data-layer, returning BusinessObjects not LINQ. DB: The SQL will be Microsoft SQL-server/Express (havent decided yet). Lets think of setup where we have a database of [Persons]. They can all have multiple [Address]es and we have a complete list of all [PostalCode] and corresponding citynames etc. The deal is that we have joined a lot of details from other tables. {Relations}/[tables] [Person]:1 --- N:{PersonAddress}:M --- 1:[Address] [Address]:N --- 1:[PostalCode] Now we want to build the DAL for Person. How should the PersonBO look and when does the joins occure? Is it a business-layer problem to fetch all citynames and possible addressses pr. Person? or should the DAL complete all this before returning the PersonBO to the BAL ? Class PersonBO { public int ID {get;set;} public string Name {get;set;} public List<AddressBO> {get;set;} // Question #1 } // Q1: do we retrieve the objects before returning the PersonBO and should it be an Array instead? or is this totally wrong for n-tier/3-tier?? Class AddressBO { public int ID {get;set;} public string StreetName {get;set;} public int PostalCode {get;set;} // Question #2 } // Q2: do we make the lookup or just leave the PostalCode for later lookup? Can anyone explain in what order to pull which objects? Constructive criticism is very welcome. :o)

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  • Google App Engine - How to implement the activity stream in a social network

    - by spidee
    I want some ideas on the best practice to implement an activity stream for a social network im building in app engine (PYTHON) I first want to keep a log for all activities of each user - so that we have a history. i.e. someone became a friend, added a picture, changed their address etc. This way we have a users history available should we need it. Also mean we can remove friendship joins, change user data but have a historical log. I also want to stream a users activity to their friends. for this only the last X activities need to be kept - that is in the scenario that messages are sent to friends when an activity occurs. Its pretty straight forward designing a history log - ie: when, what, where. The complication comes as to how we notify friends of a user as to their activity. In our app friendships are not mutual - ie they are based on the twitter following model. Some accounts could have thousands of followers. What is the best approach to model this. using a many to many join table and doing a costly query - using a feed class that fired a copy of the activity to all the subscribers - maybe into mcache? As their maybe a need to fire thousands of messages i would imagine a cron job would need to be used. Any help ideas thoughts on this Thx

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  • Java Archtecture Decision !!

    - by santiagobasulto
    Hi everybody! I'm developing a medium Java app, and i'm facing a small problem due to my lack of expirience. I've a custom DAO, which gets "Article" objects from the DataBase. I've the Article class, and the DAO has a method called getArticle(int id), this method returns an Article. The Article has a Category object, and i'm using lazy loading. So, when i request for an Article Category (Article a = new Article(); a.getCategory();) the Article class gets the Category from the DAO and then returns it. I'm now thinking to cache it, so when i request multiple times to an Article's category, the database is only queried one time. My question is: where should i put that cache? I can put it on the Article class (in the DTO), or i can put it on the DAO class. What do you say? Thanks!

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