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  • Binding XML in Sliverlight without Nominal Classes

    - by AnthonyWJones
    Lets say I have a simple chunck of XML:- <root> <item forename="Fred" surname="Flintstone" /> <item forename="Barney" surname="Rubble" /> </root> Having fetched this XML in Silverlight I would like to bind it with xaml of this ilke:- <ListBox x:Name="ItemList" Style="{StaticResource Items}"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel Orientation="Horizontal"> <TextBox Text="{Binding Forename}" /> <TextBox Text="{Binding Surname}" /> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> </ListBox> Now I can bind simply enough with LINQ to XML and a nominal class:- public class Person { public string Forename {get; set;} public string Surname {get; set;} } So here is the question, can it be done without this class? IOW coupling between the Sliverlight code and the input XML is limited to the XAML only, other source code is agnostic to the set of attributes on the item element. Edit: The use of XSD is suggested but ultimately it amounts the same thing. XSD-Generated class. Edit: An anonymous class doesn't work, Silverlight can't bind them. Edit: This needs to be two way, the user needs to be able to edit the values and these value end up in the XML. (Changed original TextBlock to TextBox in sample above).

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  • Database warehouse design: fact tables and dimension tables

    - by morpheous
    I am building a poor man's data warehouse using a RDBMS. I have identified the key 'attributes' to be recorded as: sex (true/false) demographic classification (A, B, C etc) place of birth date of birth weight (recorded daily): The fact that is being recorded My requirements are to be able to run 'OLAP' queries that allow me to: 'slice and dice' 'drill up/down' the data and generally, be able to view the data from different perspectives After reading up on this topic area, the general consensus seems to be that this is best implemented using dimension tables rather than normalized tables. Assuming that this assertion is true (i.e. the solution is best implemented using fact and dimension tables), I would like to seek some help in the design of these tables. 'Natural' (or obvious) dimensions are: Date dimension Geographical location Which have hierarchical attributes. However, I am struggling with how to model the following fields: sex (true/false) demographic classification (A, B, C etc) The reason I am struggling with these fields is that: They have no obvious hierarchical attributes which will aid aggregation (AFAIA) - which suggest they should be in a fact table They are mostly static or very rarely change - which suggests they should be in a dimension table. Maybe the heuristic I am using above is too crude? I will give some examples on the type of analysis I would like to carryout on the data warehouse - hopefully that will clarify things further. I would like to aggregate and analyze the data by sex and demographic classification - e.g. answer questions like: How does male and female weights compare across different demographic classifications? Which demographic classification (male AND female), show the most increase in weight this quarter. etc. Can anyone clarify whether sex and demographic classification are part of the fact table, or whether they are (as I suspect) dimension tables.? Also assuming they are dimension tables, could someone elaborate on the table structures (i.e. the fields)? The 'obvious' schema: CREATE TABLE sex_type (is_male int); CREATE TABLE demographic_category (id int, name varchar(4)); may not be the correct one.

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  • What is your best-practice advice on implementing SQL stored procedures (in a C# winforms applicatio

    - by JYelton
    I have read these very good questions on SO about SQL stored procedures: When should you use stored procedures? and Are Stored Procedures more efficient, in general, than inline statements on modern RDBMS’s? I am a beginner on integrating .NET/SQL though I have used basic SQL functionality for more than a decade in other environments. It's time to advance with regards to organization and deployment. I am using .NET C# 3.5, Visual Studio 2008 and SQL Server 2008; though this question can be regarded as language- and database- agnostic, meaning that it could easily apply to other environments that use stored procedures and a relational database. Given that I have an application with inline SQL queries, and I am interested in converting to stored procedures for organizational and performance purposes, what are your recommendations for doing so? Here are some additional questions in my mind related to this subject that may help shape the answers: Should I create the stored procedures in SQL using SQL Management Studio and simply re-create the database when it is installed for a client? Am I better off creating all of the stored procedures in my application, inside of a database initialization method? It seems logical to assume that creating stored procedures must follow the creation of tables in a new installation. My database initialization method creates new tables and inserts some default data. My plan is to create stored procedures following that step, but I am beginning to think there might be a better way to set up a database from scratch (such as in the installer of the program). Thoughts on this are appreciated. I have a variety of queries throughout the application. Some queries are incredibly simple (SELECT id FROM table) and others are extremely long and complex, performing several joins and accepting approximately 80 parameters. Should I replace all queries with stored procedures, or only those that might benefit from doing so? Finally, as this topic obviously requires some research and education, can you recommend an article, book, or tutorial that covers the nuances of using stored procedures instead of direct statements?

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  • Find unique vertices from a 'triangle-soup'

    - by sum1stolemyname
    I am building a CAD-file converter on top of two libraries (Opencascade and DWF Toolkit). However, my question is plattform agnostic: Given: I have generated a mesh as a list of triangular faces form a model constructed through my application. Each Triangle is defined through three vertexes, which consist of three floats (x, y & z coordinate). Since the triangles form a mesh, most of the vertices are shared by more then one triangle. Goal: I need to find the list of unique vertices, and to generate an array of faces consisting of tuples of three indices in this list. What i want to do is this: //step 1: build a list of unique vertices for each triangle for each vertex in triangle if not vertex in listOfVertices Add vertex to listOfVertices //step 2: build a list of faces for each triangle for each vertex in triangle Get Vertex Index From listOfvertices AddToMap(vertex Index, triangle) While I do have an implementation which does this, step1 (the generation of the list of unique vertices) is really slow in the order of O(n!), since each vertex is compared to all vertices already in the list. I thought "Hey, lets build a hashmap of my vertices' components using std::map, that ought to speed things up!", only to find that generating a unique key from three floating point values is not a trivial task. Here, the experts of stackoverflow come into play: I need some kind of hash-function which works on 3 floats, or any other function generating a unique value from a 3d-vertex position.

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  • Newbie question about Java

    - by Rob Nicholson
    Okay, I know that Java is a language but somebody has asked me if they can write a web application to interface in with a web app I've written in ASP.NET. I'm implementing a web service to serve up an XML so it's pretty language agnostic. However, I'm not 100% sure whether going down the Java route makes a lot of sense. I was kind of expecting PHP or ASP.NET server side code with maybe some Ajax/JavaScript or maybe a heavier client JavaScript program using JScript. Could some kind sole explain the basic Java environment when it comes with webapps. I've inferred the following - am I barking up the right tree? Java when run like ASP.NET is called JSP JavaBeans is a bit like the .NET framework, i.e. it's a library of re-usable components Java EE is a bit like ASP.NET in that it's a framework for building web pages on a server Java can also run on the client but it needs the Java VM installing When running Java on the client, can you use JavaBeans and is there a framework? Can it also use JScript? I don't think so as JScript is JavaScript library. Whilst running Java on the server would be okay, this is a relatively small application and therefore Java sounds like a bit of overkill. PHP or ASP.NET feels a better fit. But I don't think they should go down the Java applet in the browser and it adds complexity that's not needed. Thanks, Rob.

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  • Database warehoue design: fact tables and dimension tables

    - by morpheous
    I am building a poor man's data warehouse using a RDBMS. I have identified the key 'attributes' to be recorded as: sex (true/false) demographic classification (A, B, C etc) place of birth date of birth weight (recorded daily): The fact that is being recorded My requirements are to be able to run 'OLAP' queries that allow me to: 'slice and dice' 'drill up/down' the data and generally, be able to view the data from different perspectives After reading up on this topic area, the general consensus seems to be that this is best implemented using dimension tables rather than normalized tables. Assuming that this assertion is true (i.e. the solution is best implemented using fact and dimension tables), I would like to see some help in the design of these tables. 'Natural' (or obvious) dimensions are: Date dimension Geographical location Which have hierarchical attributes. However, I am struggling with how to model the following fields: sex (true/false) demographic classification (A, B, C etc) The reason I am struggling with these fields is that: They have no obvious hierarchical attributes which will aid aggregation (AFAIA) - which suggest they should be in a fact table They are mostly static or very rarely change - which suggests they should be in a dimension table. Maybe the heuristic I am using above is too crude? I will give some examples on the type of analysis I would like to carryout on the data warehouse - hopefully that will clarify things further. I would like to aggregate and analyze the data by sex and demographic classification - e.g. answer questions like: How does male and female weights compare across different demographic classifications? Which demographic classification (male AND female), show the most increase in weight this quarter. etc. Can anyone clarify whether sex and demographic classification are part of the fact table, or whether they are (as I suspect) dimension tables.? Also assuming they are dimension tables, could someone elaborate on the table structures (i.e. the fields)? The 'obvious' schema: CREATE TABLE sex_type (is_male int); CREATE TABLE demographic_category (id int, name varchar(4)); may not be the correct one.

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  • SharePoint 2007 and SiteMinder

    - by pborovik
    Here is a question regarding some details how SiteMinder secures access to the SharePoint 2007. I've read a bunch of materials regarding this and have some picture for SharePoint 2010 FBA claims-based + SiteMinder security (can be wrong here, of course): SiteMinder is registered as a trusted identity provider for the SharePoint; It means (to my mind) that SharePoint has no need to go into all those user directories like AD, RDBMS or whatever to create a record for user being granted access to SharePoint - instead it consumes a claims-based id supplied by SiteMinder SiteMinder checks all requests to SharePoint resources and starts login sequence via SiteMinder if does not find required headers in the request (SMSESSION, etc.) SiteMinder creates a GenericIdentity with the user login name if headers are OK, so SharePoint recognizes the user as authenticated But in the case of SharePoint 2007 with FBA + SiteMinder, I cannot find an answer for questions like: Does SharePoint need to go to all those user directories like AD to know something about users (as SiteMinder is not in charge of providing user info like claims-based ids)? So, SharePoint admin should configure SharePoint FBA to talk to these sources? Let's say I'm talking to a Web Service of SharePoint protected by SiteMinder. Shall I make a Authentication.asmx-Login call to create a authentication ticket or this schema is somehow changed by the SiteMinder? If such call is needed, do I also need a SiteMinder authentication sequence? What prevents me from rewriting request headers (say, manually in Fiddler) before posting request to the SharePoint protected by SiteMinder to override its defence? Pity, but I do not have access to deployed SiteMinder + SharePoint, so need to investigate some question blindly. Thanks.

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  • Workflow engine BPMN, Drools, etc or ESB?

    - by Tom
    We currently have an application that is based on an in-house developed workflow engine with YAML based DSL. We are looking to move parts of it to Java. I have discovered a number of java solutions like Intalio, JBPM, Drools Expert, Drools Flow etc. They appear to be aimed at businesses where the business analyst creates the workflows using a graphical editor and submits them to the workflow engine. They seem geared towards ease of use for non-technical people rather than for developers with a focus on human interaction. The workflows tend to look like. Discover-a-file -\ -> join -> process-file -> move-file -> register-file Discover-some-metadata -/ If any step fails we need to retry it X times. We also need to be able to stop the system and be able to restart it and have it continue from where it was (durable). Some of our workflows can be defined by a set of goals we need to achieve so Jess's backwards rule chaining sounds interesting but it is not open source. It might be that what we are after is a Finite State Machine engine or just an Enterprise Service Bus and do everything as JMS queues. Is there a good open source workflow engine that is both standards-based but also geared towards developers. We don't particular want to use a graphical workflow designer or write reams of XML and it should ideally be in Java or language agnostic (makes REST/Soap calls to external services). Thanks, Tom

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  • Troubles with PyDev and external libraries in OS X

    - by Davide Gualano
    I've successfully installed the latest version of PyDev in my Eclipse (3.5.1) under OS X 10.6.3, with python 2.6.1 I have troubles in making the libraries I have installed work. For example, I'm trying to use the cx_Oracle library, which is perfectly working if called from the python interpeter of from simple scripts made with some text editor. But I cant make it work inside Eclipse: I have this small piece of code: import cx_Oracle conn = cx_Oracle.connect(CONN_STRING) sql = "select field from mytable" cursor = conn.cursor() cursor.execute(sql) for row in cursor: field = row[0] print field If I execute it from Eclipse, I get the following error: import cx_Oracle File "build/bdist.macosx-10.6-universal/egg/cx_Oracle.py", line 7, in <module> File "build/bdist.macosx-10.6-universal/egg/cx_Oracle.py", line 6, in __bootstrap__ ImportError: dlopen(/Users/dave/.python-eggs/cx_Oracle-5.0.3-py2.6-macosx-10.6-universal.egg-tmp/cx_Oracle.so, 2): Library not loaded: /b/227/rdbms/lib/libclntsh.dylib.10.1 Referenced from: /Users/dave/.python-eggs/cx_Oracle-5.0.3-py2.6-macosx-10.6-universal.egg-tmp/cx_Oracle.so Reason: no suitable image found. Did find: /Users/dave/lib/libclntsh.dylib.10.1: mach-o, but wrong architecture Same snippet works perfectly from the python shell I have configured the interpeter in Eclipse in preferences - PyDev -- Interpreter - Python, using the Auto Config option and selecting all the libs found. What am I doing wrong here? Edit: launching file /Users/dave/.python-eggs/cx_Oracle-5.0.3-py2.6-macosx-10.6-universal.egg-tmp/cx_Oracle.so from the command line tells this: /Users/dave/.python-eggs/cx_Oracle-5.0.3-py2.6-macosx-10.6-universal.egg-tmp/cx_Oracle.so: Mach-O universal binary with 3 architectures /Users/dave/.python-eggs/cx_Oracle-5.0.3-py2.6-macosx-10.6-universal.egg-tmp/cx_Oracle.so (for architecture i386): Mach-O bundle i386 /Users/dave/.python-eggs/cx_Oracle-5.0.3-py2.6-macosx-10.6-universal.egg-tmp/cx_Oracle.so (for architecture ppc7400): Mach-O bundle ppc /Users/dave/.python-eggs/cx_Oracle-5.0.3-py2.6-macosx-10.6-universal.egg-tmp/cx_Oracle.so (for architecture x86_64): Mach-O 64-bit bundle x86_64

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  • Is it possible that a single-threaded program is executed simultaneously on more than one CPU core?

    - by Wolfgang Plaschg
    When I run a single-threaded program that i have written on my quad core Intel i can see in the Windows Task Manager that actually all four cores of my CPU are more or less active. One core is more active than the other three, but there is also activity on those. There's no other program (besided the OS kernel of course) running that would be plausible for that activitiy. And when I close my program all activity an all cores drops down to nearly zero. All is left is a little "noise" on the cores, so I'm pretty sure all the visible activity comes directly or indirectly (like invoking system routines) from my program. Is it possible that the OS or the cores themselves try to balance some code or execution on all four cores, even it's not a multithreaded program? Do you have any links that documents this technique? Some infos to the program: It's a console app written in Qt, the Task Manager states that only one thread is running. Maybe Qt uses threads, but I don't use signals or slots, nor any GUI. Link to Task Manager screenshot: http://img97.imageshack.us/img97/6403/taskmanager.png This question is language agnostic and not tied to Qt/C++, i just want to know if Windows or Intel do to balance also single-threaded code on all cores. If they do, how does this technique work? All I can think of is, that kernel routines like reading from disk etc. is scheduled on all cores, but this won't improve performance significantly since the code still has to run synchronous to the kernel api calls. EDIT Do you know any tools to do a better analysis of single and/or multi-threaded programs than the poor Windows Task Manager?

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  • Why is OpenSubKey() returning null on my Win 7 64 bit system?

    - by BrMcMullin
    Has anyone seen OpenSubKey() and other Microsoft.Win32 registry functions return null on 64 bit systems when 32 bit registry keys are under Wow6432node in the registry? I'm working on a unit testing framework that makes a call to OpenSubKey() from the .net library. My dev system is a Win 7 64 bit environment with VS 2008 SP1 and the Win 7 SDK installed. The application we're unit testing is a 32 bit application, so the registry is virtualized under HKLM\Software\Wow6432node. When we call: Registry.LocalMachine.OpenSubKey( @"Software\MyCompany\MyApp\" ); Null is returned, however explicitly stating to look here works: Registry.LocalMachine.OpenSubKey( @"Software\Wow6432node\MyCompany\MyApp\" ); From what I understand this function should be agnostic to 32 bit or 64 bit environments and should know to jump to the virtual node. Even stranger is the fact that the exact same call inside a compiled and installed version of our application is running just fine on the same system and is getting the registry keys necessary to run; which are also being placed in HKLM\Software\Wow6432node. Any suggestions? Thanks in advance!

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  • mod_cgi , mod_fastcgi, mod_scgi , mod_wsgi, mod_python, FLUP. I don't know how many more. what is mo

    - by claws
    I recently learnt Python. I liked it. I just wanted to use it for web development. This thought caused all the troubles. But I like these troubles :) Coming from PHP world where there is only one way standardized. I expected the same and searched for python & apache. http://stackoverflow.com/questions/449055/setting-up-python-on-windows-apache says Stay away from mod_python. One common misleading idea is that mod_python is like mod_php, but for python. That is not true. So what is equivalent of mod_php in python? I need little clarification on this one http://stackoverflow.com/questions/219110/how-python-web-frameworks-wsgi-and-cgi-fit-together CGI, FastCGI and SCGI are language agnostic. You can write CGI scripts in Perl, Python, C, bash, or even Assembly :). So, I guess mod_cgi , mod_fastcgi, mod_scgi are their corresponding apache modules. Right? WSGI is some kind of optimized/improved inshort an efficient version specifically designed for python language only. In order to use this mod_wsgi is a way to go. right? This leaves out mod_python. What is it then? Apache - mod_fastcgi - FLUP (via CGI protocol) - Django (via WSGI protocol) Flup is another way to run with wsgi for any webserver that can speak FCGI, SCGI or AJP What is FLUP? What is AJP? How did Django come in the picture? These questions raise quetions about PHP. How is it actually running? What technology is it using? mod_php & mod_python what are the differences? In future if I want to use Perl or Java then again will I have to get confused? Kindly can someone explain things clearly and give a Complete Picture.

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  • Perform Grouping of Resultsets in Code, not on Database Level

    - by NinjaBomb
    Stackoverflowers, I have a resultset from a SQL query in the form of: Category Column2 Column3 A 2 3.50 A 3 2 B 3 2 B 1 5 ... I need to group the resultset based on the Category column and sum the values for Column2 and Column3. I have to do it in code because I cannot perform the grouping in the SQL query that gets the data due to the complexity of the query (long story). This grouped data will then be displayed in a table. I have it working for specific set of values in the Category column, but I would like a solution that would handle any possible values that appear in the Category column. I know there has to be a straightforward, efficient way to do it but I cannot wrap my head around it right now. How would you accomplish it? EDIT I have attempted to group the result in SQL using the exact same grouping query suggested by Thomas Levesque and both times our entire RDBMS crashed trying to process the query. I was under the impression that Linq was not available until .NET 3.5. This is a .NET 2.0 web application so I did not think it was an option. Am I wrong in thinking that? EDIT Starting a bounty because I believe this would be a good technique to have in the toolbox to use no matter where the different resultsets are coming from. I believe knowing the most concise way to group any 2 somewhat similar sets of data in code (without .NET LINQ) would be beneficial to more people than just me.

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  • Great examples of self-paced labs and exercises

    - by Mayo
    It is probably a safe bet that many of us are what they call Tactile / Kinesthetic Learners meaning that we learn best when we are physically doing something as opposed to listening to an online tutorial or reading a book. My goal with this question is to derive a list of books or online resources that serve as superb examples of self-paced programming labs and exercises. For example, I was extremely impressed with the SportsStore exercise in Steven Sanderson's Pro ASP.NET MVC Framework. The exercise spanned multiple chapters and gradually introduced new topics. I was also impressed with the materials associated with the Windows Azure Boot Camp. The demos and lab materials, accessible through the website, allow us to practice and reinforce what we can read about in articles and books. Please list any examples you might have, one per submission, below. The question is language/platform agnostic. Suggestions can be generic or specific to a given technology (PHP, SQL Server, Azure, Flash, Objective C, etc.). I only ask that the answers pertain to labs and exercises that relate to programming. My hope is that the best answers will float to the top allowing developers to review the top answers and find another programming topic that can be learned through example.

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  • Parsing basic math equations for children's educational software?

    - by Simucal
    Inspired by a recent TED talk, I want to write a small piece of educational software. The researcher created little miniature computers in the shape of blocks called "Siftables". [David Merril, inventor - with Siftables in the background.] There were many applications he used the blocks in but my favorite was when each block was a number or basic operation symbol. You could then re-arrange the blocks of numbers or operation symbols in a line, and it would display an answer on another siftable block. So, I've decided I wanted to implemented a software version of "Math Siftables" on a limited scale as my final project for a CS course I'm taking. What is the generally accepted way for parsing and interpreting a string of math expressions, and if they are valid, perform the operation? Is this a case where I should implement a full parser/lexer? I would imagine interpreting basic math expressions would be a semi-common problem in computer science so I'm looking for the right way to approach this. For example, if my Math Siftable blocks where arranged like: [1] [+] [2] This would be a valid sequence and I would perform the necessary operation to arrive at "3". However, if the child were to drag several operation blocks together such as: [2] [\] [\] [5] It would obviously be invalid. Ultimately, I want to be able to parse and interpret any number of chains of operations with the blocks that the user can drag together. Can anyone explain to me or point me to resources for parsing basic math expressions? I'd prefer as much of a language agnostic answer as possible.

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  • How to setup Lucene search for a B2B web app?

    - by Bill Paetzke
    Given: 5000 databases (spread out over 5 servers) 1 database per client (so you can infer there are 1000 clients) 2 to 2000 users per client (let's say avg is 100 users per client) Clients (databases) come and go every day (let's assume most remain for at least one year) Let's stay agnostic of language or sql brand, since Lucene (and Solr) have a breadth of support The Question: How would you setup Lucene search so that each client can only search within its database? How would you setup the index(es)? Would you need to add a filter to all search queries? If a client cancelled, how would you delete their (part of the) index? (this may be trivial--not sure yet) Possible Solutions: Make an index for each client (database) Pro: Search is faster (than one-index-for-all method). Indices are relative to the size of the client's data. Con: I'm not sure what this entails, nor do I know if this is beyond Lucene's scope. Have a single, gigantic index with a database_name field. Always include database_name as a filter. Pro: Not sure. Maybe good for tech support or billing dept to search all databases for info. Con: Search is slower (than index-per-client method). Flawed security if query filter removed. For Example: Joel Spolsky said in Podcast #11 that his hosted web app product, FogBugz On-Demand, uses Lucene. He has thousands of on-demand clients. And each client gets their own database. His situation is quite similar to mine. Although, he didn't elaborate on the setup (particularly indices); hence, the need for this question. One last thing: I would also accept an answer that uses Solr (the extension of Lucene). Perhaps it's better suited for this problem. Not sure.

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  • Embedded non-relational (nosql) data store

    - by Igor Brejc
    I'm thinking about using/implementing some kind of an embedded key-value (or document) store for my Windows desktop application. I want to be able to store various types of data (GPS tracks would be one example) and of course be able to query this data. The amount of data would be such that it couldn't all be loaded into memory at the same time. I'm thinking about using sqlite as a storage engine for a key-value store, something like y-serial, but written in .NET. I've also read about FriendFeed's usage of MySQL to store schema-less data, which is a good pointer on how to use RDBMS for non-relational data. sqlite seems to be a good option because of its simplicity, portability and library size. My question is whether there are any other options for an embedded non-relational store? It doesn't need to be distributable and it doesn't have to support transactions, but it does have to be accessible from .NET and it should have a small download size. UPDATE: I've found an article titled SQLite as a Key-Value Database which compares sqlite with Berkeley DB, which is an embedded key-value store library.

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  • Why put a DAO layer over a persistence layer (like JDO or Hibernate)

    - by Todd Owen
    Data Access Objects (DAOs) are a common design pattern, and recommended by Sun. But the earliest examples of Java DAOs interacted directly with relational databases -- they were, in essence, doing object-relational mapping (ORM). Nowadays, I see DAOs on top of mature ORM frameworks like JDO and Hibernate, and I wonder if that is really a good idea. I am developing a web service using JDO as the persistence layer, and am considering whether or not to introduce DAOs. I foresee a problem when dealing with a particular class which contains a map of other objects: public class Book { // Book description in various languages, indexed by ISO language codes private Map<String,BookDescription> descriptions; } JDO is clever enough to map this to a foreign key constraint between the "BOOKS" and "BOOKDESCRIPTIONS" tables. It transparently loads the BookDescription objects (using lazy loading, I believe), and persists them when the Book object is persisted. If I was to introduce a "data access layer" and write a class like BookDao, and encapsulate all the JDO code within this, then wouldn't this JDO's transparent loading of the child objects be circumventing the data access layer? For consistency, shouldn't all the BookDescription objects be loaded and persisted via some BookDescriptionDao object (or BookDao.loadDescription method)? Yet refactoring in that way would make manipulating the model needlessly complicated. So my question is, what's wrong with calling JDO (or Hibernate, or whatever ORM you fancy) directly in the business layer? Its syntax is already quite concise, and it is datastore-agnostic. What is the advantage, if any, of encapsulating it in Data Access Objects?

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  • Comet, responseText and memory usage

    - by ithcy
    Is there a way to clear out the responseText of an XHR object without destroying the XHR object? I need to keep a persistent connection open to a web server to feed live data to a browser. The problem is, there is a relatively large amount of data coming through (several hundred K per second constantly), so memory usage is a big problem, because this connection must remain open for at least several minutes. responseText gets very big very quickly, even though the JSON I send back has been crunched as small as it can get. Due to the way the server-side app works, if I use AJAX-style short polling and just destroy the XHR object when I'm done with it, I miss significant amounts of important data even in the few milliseconds it takes to parse the response, create a new XHR and send it out. I do not have the option to use overlapping requests, as the web server only accepts one connection at a time. (Don't ask.) So Comet is exactly the model I need. What I would like to do is parse each JSON chunk as it comes back from the server, and then clear out responseText so that I can keep using the same connection. However, responseText is read-only. It cannot be directly emptied by any method I have found. Is there a part of the picture I am missing here? Does anyone know any tricks I can use to free up responseText when I'm done reading it? Or is there another place the server responses can go? I am not including code because this is really almost a code-agnostic question. The Javascript routines that spawn the XHRs and handle the returned data are very, very simple.

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  • Embedding Lua functions as member variables in Java

    - by Zarion
    Although the program I'm working on is in Java, answering this from a C perspective is also fine, considering that most of this is either language-agnostic, or happens on the Lua side of things. In the outline I have for the architecture of a game I'm programming, individual types of game objects within a particular class (eg: creatures, items, spells, etc.) are loaded from a data file. Most of their properties are simple data types, but I'd like a few of these members to actually contain simple scripts that define, for example, what an item does when it's used. The scripts will be extremely simple, since all fundamental game actions will be exposed through an API from Java. The Lua is simply responsible for stringing a couple of these basic functions together, and setting arguments. The question is largely about the best way to store a reference to a specific Lua function as a member of a Java class. I understand that if I store the Lua code as a string and call lua_dostring, Lua will compile the code fresh every time it's called. So the function needs to be defined somehow, and a reference to this specific function wrapped in a Java function object. One possibility that I've considered is, during the data loading process, when the loader encounters a script definition in a data file, it extracts this string, decorates the function name using the associated object's unique ID, calls lua_dostring on the string containing a full function definition, and then wraps the generated function name in a Java function object. A function declared in script run with lua_dostring should still be added to the global function table, correct? I'm just wondering if there's a better way of going about this. I admit that my knowledge of Lua at this point is rather superficial and theoretical, so it's possible that I'm overlooking something obvious.

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  • What ORM for .NET should I use?

    - by eKek0
    I'm relatively new to .NET and have being using Linq2Sql for a almost a year, but it lacks some of the features I'm looking for now. I'm going to start a new project in which I want to use an ORM with the following characteristics: It has to be very productive, I don't want to be dealing with the access layer to save or retrieve objects from or to the database, but it should allows me to easily tweak any object before actually commit it to the database; also it should allows me to work easily with a changing database schema It should allows me to extend the objects mapped from the database, for example to add virtual attributes to them (virtual columns to a table) It has to be (at least almost) database agnostic, it should allows me to work with different databases in a transparent way It has to have not so much configuration or must be based on conventions to make it work It should allows me to work with Linq So, do you know any ORM that I could use? Thank you for your help. EDIT I know that an option is to use NHibernate. This appears as the facto standard for enterprise level applications, but also it seems that is not very productive because its deep learning curve. In other way, I have read in some other post here in SO that it doesn't integrate well with Linq. Is all of that true?

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  • How to query JDO persistent objects in unowned relationship model?

    - by Paul B
    Hello, I'm trying to migrate my app from PHP and RDBMS (MySQL) to Google App Engine and have a hard time figuring out data model and relationships in JDO. In my current app I use a lot of JOIN queries like: SELECT users.name, comments.comment FROM users, comments WHERE users.user_id = comments.user_id AND users.email = '[email protected]' As I understand, JOIN queries are not supported in this way so the only(?) way to store data is using unowned relationships and "foreign" keys. There is a documentation regarding that, but no useful examples. So far I have something like this: @PersistenceCapable public class Users {     @PrimaryKey     @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)     private Key key;     @Persistent     private String name;         @Persistent     private String email;         @Persistent     private Set<Key> commentKeys;     // Accessors... } @PersistenceCapable public class Comments {     @PrimaryKey     @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)     private Key key;     @Persistent     private String comment;         @Persistent     private Date commentDate;     @Persistent     private Key userKey;     // Accessors... } So, how do I get a list with commenter's name, comment and date in one query? I see how I probably could get away with 3 queries but that seems wrong and would create unnecessary overhead. Please, help me out with some code examples. -- Paul.

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  • What is the most efficient/elegant way to parse a flat table into a tree?

    - by Tomalak
    Assume you have a flat table that stores an ordered tree hierarchy: Id Name ParentId Order 1 'Node 1' 0 10 2 'Node 1.1' 1 10 3 'Node 2' 0 20 4 'Node 1.1.1' 2 10 5 'Node 2.1' 3 10 6 'Node 1.2' 1 20 What minimalistic approach would you use to output that to HTML (or text, for that matter) as a correctly ordered, correctly intended tree? Assume further you only have basic data structures (arrays and hashmaps), no fancy objects with parent/children references, no ORM, no framework, just your two hands. The table is represented as a result set, which can be accessed randomly. Pseudo code or plain English is okay, this is purely a conceptional question. Bonus question: Is there a fundamentally better way to store a tree structure like this in a RDBMS? EDITS AND ADDITIONS To answer one commenter's (Mark Bessey's) question: A root node is not necessary, because it is never going to be displayed anyway. ParentId = 0 is the convention to express "these are top level". The Order column defines how nodes with the same parent are going to be sorted. The "result set" I spoke of can be pictured as an array of hashmaps (to stay in that terminology). For my example was meant to be already there. Some answers go the extra mile and construct it first, but thats okay. The tree can be arbitrarily deep. Each node can have N children. I did not exactly have a "millions of entries" tree in mind, though. Don't mistake my choice of node naming ('Node 1.1.1') for something to rely on. The nodes could equally well be called 'Frank' or 'Bob', no naming structure is implied, this was merely to make it readable. I have posted my own solution so you guys can pull it to pieces.

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  • High memory usage for dummies

    - by zaf
    I've just restarted my firefox web browser again because it started stuttering and slowing down. This happens every other day due to (my understanding) of excessive memory usage. I've noticed it takes 40M when it starts and then, by the time I notice slow down, it goes to 1G and my machine has nothing more to offer unless I close other applications. I'm trying to understand the technical reasons behind why its such a difficult problem to sol ve. Mozilla have a page about high memory usage: http://support.mozilla.com/en-US/kb/High+memory+usage But I'm looking for a slightly more in depth and satisfying explanation. Not super technical but enough to give the issue more respect and please the crowd here. Some questions I'm already pondering (they could be silly so take it easy): When I close all tabs, why doesn't the memory usage go all the way down? Why is there no limits on extensions/themes/plugins memory usage? Why does the memory usage increase if it's left open for long periods of time? Why are memory leaks so difficult to find and fix? App and language agnostic answers also much appreciated.

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  • Representing complex scheduled reoccurance in a database

    - by David Pfeffer
    I have the interesting problem of representing complex schedule data in a database. As a guideline, I need to be able to represent the entirety of what the iCalendar -- ics -- format can represent, but in a database. I'm not actually implementing anything relating to ics, but it gives a good scope of the type of rules I need to be able to model. I need to allow allow representation of a single event or a reoccurring event based on multiple times per day, days of the week, week of a month, month, year, or some combination of those. For example, the third Thursday in November annually, or the 25th of December annually, or every two weeks starting November 2 and continuing until September 8 the following year. I don't care about insertion efficiency but query efficiency is critical. The operation I will be doing most often is providing either a single date/time or a date/time range, and trying to determine if the defined schedule matches any part of the date/time range. Other operations can be slower. For example, given January 15, 2010 at 10:00 AM through January 15, 2010 at 11:00 AM, find all schedules that match at least part of that time. (i.e. a schedule that covers 10:30 - 11:00 still matches.) Any suggestions? I looked at http://stackoverflow.com/questions/1016170/how-would-one-represent-scheduled-events-in-an-rdbms but it doesn't cover the scope of the type of reoccurance rules I'd like to model.

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