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  • How does one implement storage/retrieval of smart-search/mailbox features?

    - by humble_coder
    Hi All, I have a question regarding implementation of smart-search features. For example, consider something like "smart mailboxes" in various email applications. Let's assume you have your data (emails) stored in a database and, depending on the field for which the query will be created, you present different options to the end user. At the moment let's assume the Subject, Verb, Object approach… For instance, say you have the following: SUBJECTs: message, to_address, from_address, subject, date_received VERBs: contains, does_not_contain, is_equal_to, greater_than, less_than OBJECTs: ??????? Now, in case it isn't clear, I want a table structure (although I'm not opposed to an external XMLesque file of some sort) to store (and later retrieve/present) my criteria for smart searches/mailboxes for later use. As an example, using SVO I could easily store then reconstruct a query for "date between two dates" -- simply use "date greater than" AND "date less than". However, what if, in the same smart search, I wanted a "between" OR'ed with another criterion? You can see that it might get out of hand -- not necessarily in the query creation (as that is rather simplistic), but in the option presentation and storage mechanism. Perhaps I need to think more on a more granular level. Perhaps I need to simply allow the user to select AND or OR for each entry independently instead of making it an ALL OR NOTHING type smart search (i.e. instead of MATCH ALL or MATCH ANY, I need to simply allow them to select -- I just don't want it to turn into a Hydra). Any input would be most appreciated. My apologies if the question is a bit incoherent. It is late, and I my brain is toast. Best.

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  • Constructor on type: "Namespace.type" not found.

    - by Nick
    Hello, I am using Castle.Windsor as an IOC. So I am trying to resolve a service type in the constructor of an HTTPHandler. I keep receiving this error, "Constructor on type: "Namespace.type" not found." My configuration has the following entries for service type: IDocumentDirectory <component id="restricted.content.directory" service="org.healthwise.foundations.services.content.IDocumentDirectory, org.healthwise.foundations.services" type="org.healthwise.foundations.services.content.RestrictedLocalizationDocumentDirectory, org.healthwise.foundations.services"> <parameters> <contentDirectory>${content.directory}</contentDirectory> <localizations> <array> <item>en-us</item> <item>es-us</item> </array> </localizations> </parameters> </component> <component id="content.directory" service="org.healthwise.foundations.services.content.IDocumentDirectory, org.healthwise.foundations.services" type="org.healthwise.foundations.services.web.client.WebServiceDocumentDirectory, org.healthwise.foundations.services.web.client"> <parameters> <webServiceURL>#{contentDirectoryWebsiteUrl}</webServiceURL> </parameters> </component> In my new handler the constructor looks like this: public HeartBeatHttpHandler(IDocumentDirectory contentDirectory) { _contentDirectory = contentDirectory; } I have never recieved this error using Castle.Windsor. Can someone explain? Thanks!

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  • Using Live Data in Database Development Work

    - by Phil Factor
    Guest Editorial for Simple-Talk Newsletter... in which Phil Factor reacts with some exasperation when coming across a report that a majority of companies were still using financial and personal data for both developing and testing database applications. If you routinely test your development work using real production data that contains personal or financial information, you are probably being irresponsible, and at worst, risking a heavy financial penalty for your company. Surprisingly, over 80% of financial companies still do this. Plenty of data breaches and fraud have happened from the use of real data for testing, and a data breach is a nightmare for any organisation that suffers one. The cost of each data breach averages out at around $7.2 million in the US in notification, escalation, credit monitoring, fines, litigation, legal costs, and lost business due to customer churn, £1.9 million in the UK. 70% of data breaches are done from within the organisation. Real data can be exploited in a number of ways for malicious or criminal purposes. It isn't just the obvious use of items such as name and address, date of birth, social security number, and credit card and bank account numbers: Data can be exploited in many subtle ways, so there are excellent reasons to ensure that a high priority is given to the detection and prevention of any data breaches. You'll never successfully guess all the ways that real data can be exploited maliciously, or the ease with which it can be accessed. It would be silly to argue that developers never need access to a copy of the database containing live data. Developers sometimes need to track a bug that can only be replicated on the data from the live database. However, it has to be done in a very restrictive harness. The law makes no distinction between development and production databases when a data breach occurs, so the data has to be held with all appropriate security measures in place. In Europe, the use of personal data for testing requires the explicit consent of the people whose data is being held. There are federal standards such as GLBA, PCI DSS and HIPAA, and most US States have privacy legislation. The task of ensuring compliance and tight security in such circumstances is an expensive and time-consuming overhead. The developer is likely to suffer investigation if a data breach occurs, even if the company manages to stay in business. Ironically, the use of copies of live data isn't usually the most effective way to develop or test your data. Data is usually time-specific and isn't usually current by the time it is used for testing, Existing data doesn't help much for new functionality, and every time the data is refreshed from production, any test data is likely to be overwritten. Also, it is not always going to test all the 'edge' conditions that are likely to flush out bugs. You still have the task of simulating the dynamics of actual usage of the database, and here you have no alternative to creating 'spoofed' data. Because of the complexities of relational data, It used to be that there was no realistic alternative to developing and testing with live data. However, this is no longer the case. Real data can be obfuscated, or it can be created entirely from scratch. The latter process used to be impractical, now that there are plenty of third-party tools to choose from. The process of obfuscation isn't risk free. The process must access the live data, and the success of the obfuscation process has to be carefully monitored. Database data security isn't an exciting topic to you or I, but to a hacker it can be an all-consuming obsession, especially if there is financial or political gain involved. This is not the sort of adversary one would wish for and it is far better to accept, and work with, security restrictions that exist for using live data in database development work, especially when the tools exist to create large realistic database test data that can be better for several aspects of testing.

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  • Data Connection Library in SharePoint Server 2010

    - by Wayne
    What is a Data Connection Library in SharePoint Server 2010? A Data Connection Library in Microsoft SharePoint Server 2010 is a library that can contain two kinds of data connections: an Office Data Connection (ODC) file or a Universal Data Connection (UDC) file. Microsoft InfoPath 2010 uses data connections that comply with the Universal Data Connection (UDC) file schema and typically have either a *.udcx or *.xml file name extension. Data sources described by these data connections are stored on the server and can be used in standard form templates and browser-enabled form templates. How to create a SharePoint Server Data Connection Library? 1. Browse to a SharePoint Server 2010 site on which you have at least Design permissions. If you are on the root site, create a new site before you continue with the next step. 2. On the Site Actions menu, click More Options. 3. On the Create page, click Library under Filter By, and then click Data Connection Library. 4. On the right side of the Create page, type a name for the library, and then click the Create button. 5. Copy the URL of the new data connection library. How to create a new data connection file in InfoPath? 1. Open InfoPath Designer 2010, click Blank Form, and then click Design Form. 2. On the Data tab, click Data Connections, and then click Add. 3. In the Data Connection Wizard, click Create a new connection to, click Receive data, and then click Next. 4. Click the kind of data source that you are connecting to, such as Database, Web service, or SharePoint library or list, and then click Next. 5. Complete the remaining steps in the Data Connection Wizard to configure your data connection, and then click Finish to return to the Data Connections dialog box. 6. In the Data Connections dialog box, click Convert to Connection File. 7. In the Convert Data Connection dialog box, enter the URL of the data connection library that you previously copied (delete "Forms/AllItems.aspx" and anything following it from the URL), enter a name for the data connection file at the end of the URL, and then click OK. It will take a few moments to convert and save the data connection file to the library. 8. Confirm that the data connection was converted successfully by examining the Details section of the Data Connections dialog box while the name of the converted data connection is selected. 9. Browse to the SharePoint data connection library, click the drop-down next to the name of the data connection, click Approve/Reject, click Approved, and then click OK. Take advantage of SharePoint Data Connection Library and other useful features of SharePoint family of products that include, SharePoint Foundation 2010, MOSS 2007 and free SharePoint templates or web parts.

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  • Dynamically specify the type in C#

    - by Lirik
    I'm creating a custom DataSet and I'm under some constrains: I want the user to specify the type of the data which they want to store. I want to reduce type-casting because I think it will be VERY expensive. I will use the data VERY frequently in my application. I don't know what type of data will be stored in the DataSet, so my initial idea was to make it a List of objects, but I suspect that the frequent use of the data and the need to type-cast will be very expensive. The basic idea is this: class DataSet : IDataSet { private Dictionary<string, List<Object>> _data; /// <summary> /// Constructs the data set given the user-specified labels. /// </summary> /// <param name="labels"> /// The labels of each column in the data set. /// </param> public DataSet(List<string> labels) { _data = new Dictionary<string, List<object>>(); foreach (string label in labels) { _data.Add(label, new List<object>()); } } #region IDataSet Members public List<string> DataLabels { get { return _data.Keys.ToList(); } } public int Count { get { _data[_data.Keys[0]].Count; } } public List<object> GetValues(string label) { return _data[label]; } public object GetValue(string label, int index) { return _data[label][index]; } public void InsertValue(string label, object value) { _data[label].Insert(0, value); } public void AddValue(string label, object value) { _data[label].Add(value); } #endregion } A concrete example where the DataSet will be used is to store data obtained from a CSV file where the first column contains the labels. When the data is being loaded from the CSV file I'd like to specify the type rather than casting to object. The data could contain columns such as dates, numbers, strings, etc. Here is what it could look like: "Date","Song","Rating","AvgRating","User" "02/03/2010","Code Monkey",4.6,4.1,"joe" "05/27/2009","Code Monkey",1.2,4.5,"jill" The data will be used in a Machine Learning/Artificial Intelligence algorithm, so it is essential that I make the reading of data very fast. I want to eliminate type-casting as much as possible, since I can't afford to cast from 'object' to whatever data type is needed on every read. I've seen applications that allow the user to pick the specific data type for each item in the csv file, so I'm trying to make a similar solution where a different type can be specified for each column. I want to create a generic solution so I don't have to return a List<object> but a List<DateTime> (if it's a DateTime column) or List<double> (if it's a column of doubles). Is there any way that this can be achieved? Perhaps my approach is wrong, is there a better approach to this problem?

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  • Spring Data Neo4J @Indexed(unique = true) not working

    - by Markus Lamm
    I'm new to Neo4J and I have, probably an easy question. There're NodeEntitys in my application, a property (name) is annotated with @Indexed(unique = true) to achieve the uniqueness like I do in JPA with @Column(unique = true). My problem is, that when I persist an entity with a name that already exists in my graph, it works fine anyway. But I expected some kind of exception here...?! Here' s an overview over basic my code: @NodeEntity public abstract class BaseEntity implements Identifiable { @GraphId private Long entityId; ... } public class Role extends BaseEntity { @Indexed(unique = true) private String name; ... } public interface RoleRepository extends GraphRepository<Role> { Role findByName(String name); } @Service public class RoleServiceImpl extends BaseEntityServiceImpl<Role> implements { private RoleRepository repository; @Override @Transactional public T save(final T entity) { return getRepository().save(entity); } } And this is my test: @Test public void testNameUniqueIndex() { final List<Role> roles = Lists.newLinkedList(service.findAll()); final String existingName = roles.get(0).getName(); Role newRole = new Role.Builder(existingName).build(); newRole = service.save(newRole); } That's the point where I expect something to go wrong! How can I ensure the uniqueness of a property, without checking it for myself?? THANKS IN ADVANCE FOR ANY IDEAS!! P.S.: I'm using neo4j 1.8.M07, spring-data-neo4j 2.1.0.BUILD-SNAPSHOT and Spring 3.1.2.RELEASE.

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  • Strange error inserting new relationship data in core-data

    - by michael
    My app will allow users to create a personalised list of events from a large list of events. I have a table view which simply displays these events, tapping on one of them takes the user to the event details view, which has a button "add to my events". In this detailed view I own the original event object, retrieved via an NSFetchedResultsController and passed to the detailed view (via a table cell, the same as the core data recipes sample). I have no trouble retrieving/displaying information from this "event". I am then trying to add it to the list of MyEvents represented by a one to many (inverse) relationship: This code: NSManagedObjectContext *context = [event managedObjectContext]; MyEvents *myEvents = (MyEvents *)[NSEntityDescription insertNewObjectForEntityForName:@"MyEvents" inManagedObjectContext:context]; [myEvents addEventObject:event];//ERROR And this code (suggested below): //would this add to or overwrite the "list" i am attempting to maintain NSManagedObjectContext *context = [event managedObjectContext]; MyEvents *myEvents = (MyEvents *)[NSEntityDescription insertNewObjectForEntityForName:@"MyEvents" inManagedObjectContext:context]; NSMutableSet *myEvent = [myEvents mutableSetValueForKey:@"event"]; [myEvent addObject:event]; //ERROR Bot produce (at the line indicated by //ERROR): *** -[NSComparisonPredicate evaluateWithObject:]: message sent to deallocated instance Seems I may have missed something fundamental. I cant glean any more information through the use of debugging tools, with my knowledge of them. 1) Is this a valid way to compile and store an editable list like this? 2) Is there a better way? 3) What could possibly be the deallocated instance in error? -- I have now modified the Event entity to have a to-many relationship called "myEvents" which referrers to itself. I can add Events to this fine, and logging the object shows the correct memory addresses appearing for the relationship after a [event addMyEventObject:event];. The same failure happens right after this however. I am still at a loss to understand what is going wrong. This is the backtrace #0 0x01f753a7 in ___forwarding___ () #1 0x01f516c2 in __forwarding_prep_0___ () #2 0x01c5aa8f in -[NSFetchedResultsController(PrivateMethods) _preprocessUpdatedObjects:insertsInfo:deletesInfo:updatesInfo:sectionsWithDeletes:newSectionNames:treatAsRefreshes:] () #3 0x01c5d63b in -[NSFetchedResultsController(PrivateMethods) _managedObjectContextDidChange:] () #4 0x0002e63a in _nsnote_callback () #5 0x01f40005 in _CFXNotificationPostNotification () #6 0x0002bef0 in -[NSNotificationCenter postNotificationName:object:userInfo:] () #7 0x01bbe17d in -[NSManagedObjectContext(_NSInternalNotificationHandling) _postObjectsDidChangeNotificationWithUserInfo:] () #8 0x01c1d763 in -[NSManagedObjectContext(_NSInternalChangeProcessing) _createAndPostChangeNotification:withDeletions:withUpdates:withRefreshes:] () #9 0x01ba25ea in -[NSManagedObjectContext(_NSInternalChangeProcessing) _processRecentChanges:] () #10 0x01bdfb3a in -[NSManagedObjectContext processPendingChanges] () #11 0x01bd0957 in _performRunLoopAction () #12 0x01f4d252 in __CFRunLoopDoObservers () #13 0x01f4c65f in CFRunLoopRunSpecific () #14 0x01f4bc48 in CFRunLoopRunInMode () #15 0x0273878d in GSEventRunModal () #16 0x02738852 in GSEventRun () #17 0x002ba003 in UIApplicationMain () Cheers.

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  • Sensitive Data Storage - Best Practices

    - by Kenneth
    I recently started working on a personal project where I was connecting to a database using Java. This got me thinking. I have to provide the login information for a database account on the DB server in order to access the database. But if I hard code it in then it would be possible for someone to decompile the program and extract that login info. If I store it in an external setup file then the same problem exists only it would be even easier for them to get it. I could encrypt the data before storing it in either place but it seems like that's not really a fail safe either and I'm no encryption expert by any means. So what are some best practices for storing sensitive setup data for a program?

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  • The Best Ways to Lock Down Your Multi-User Computer

    - by Lori Kaufman
    Whether you’re sharing a computer with other family members or friends at home, or securing computers in a corporate environment, there may be many reasons why you need to protect the programs, data, and settings on the computers. This article presents multiple ways of locking down a Windows 7 computer, depending on the type of usage being employed by the users. You may need to use a combination of several of the following methods to protect your programs, data, and settings. How to Stress Test the Hard Drives in Your PC or Server How To Customize Your Android Lock Screen with WidgetLocker The Best Free Portable Apps for Your Flash Drive Toolkit

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  • WCF/ADO.NET Data Services - Could not load type 'System.Data.Services.Providers.IDataServiceUpdatePr

    - by Sahil Malik
    Ad:: SharePoint 2007 Training in .NET 3.5 technologies (more information). When you try accessing ListData.svc, do you get the following error? Could not load type 'System.Data.Services.Providers.IDataServiceUpdateProvider' from assembly 'System.Data.Services, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. Well, if you followed the instructions in Chapter 1 of my book to build your VM, you wouldn’t run into the above issue. But if you do, you need to install  -   For Windows Vista and Windows 2008 - http://www.microsoft.com/downloads/details.aspx?familyid=4B710B89-8576-46CF-A4BF-331A9306D555&displaylang=en For Windows 7 and Windows 2008 R2 - http://www.microsoft.com/downloads/details.aspx?familyid=79d7f6f8-d6e9-4b8c-8640-17f89452148e&displaylang=en Remember to: a) Install the x64 version, and b) Do an IISReset before trying again. Comment on the article ....

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  • Passing data from one database to another database table (Access) (C#)

    - by SAMIR BHOGAYTA
    string conString = "Provider=Microsoft.Jet.OLEDB.4.0 ;Data Source=Backup.mdb;Jet OLEDB:Database Password=12345"; OleDbConnection dbconn = new OleDbConnection(); OleDbDataAdapter dAdapter = new OleDbDataAdapter(); OleDbCommand dbcommand = new OleDbCommand(); try { if (dbconn.State == ConnectionState.Closed) dbconn.Open(); string selQuery = "INSERT INTO [Master] SELECT * FROM [MS Access;DATABASE="+ "\\Data.mdb" + ";].[Master]"; dbcommand.CommandText = selQuery; dbcommand.CommandType = CommandType.Text; dbcommand.Connection = dbconn; int result = dbcommand.ExecuteNonQuery(); } catch(Exception ex) {}

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  • SQL SERVER – Integration Services Balanced Data Distributor – SSIS Balanced Data Distributor

    - by pinaldave
    Microsoft SSIS Balanced Data Distributor (BDD) is a new SSIS transform. This transform takes a single input and distributes the incoming rows to one or more outputs uniformly via multithreading. The transform takes one pipeline buffer worth of rows at a time and moves it to the next output in a round robin fashion. It’s balanced and synchronous so if one of the downstream transforms or destinations is slower than the others, the rest of the pipeline will stall so this transform works best if all of the outputs have identical transforms and destinations. Download SQL Server Integration Services Balanced Data Distributor Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Documentation, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Yes, you can benefit from both data and backup compression

    - by AaronBertrand
    Earlier today, MSSQLTips posted a backup compression tip by Thomas LaRock ( blog | twitter ). In that article, Tom states: "If you are already compressing data then you will not see much benefit from backup compression." I don't want to argue with a rock star, and I will concede that he may be right in some scenarios. Nonetheless, I tweeted that "it depends;" Thomas then asked for "an example where you have data comp and you also see a large benefit from backup comp?" My initial reaction came about...(read more)

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  • Update/Insert With ADF Web Service Data Control

    - by shay.shmeltzer
    The Web service data control (WSDC) in ADF is a powerful feature that allows you to easily build a UI on top of WS interfaces exposed by other systems. However when you drag a WSDC to a page you usually get a set of output components where the data is shown. So how would you actually do an update operation on those values? The answer is that you need a call to another method in your WSDC that does the update - but what if you want to pass to it the actual values that you get from the get method you invoked before? Here is a demo showing how to do that: The two tricks that are shown here are: Changing the properties of items in the DC to be updateable - this gives you inputText fields instead of outputText fields. And passing the currentRow.dataProvider to the update method (and choosing the right iterator for this).

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  • Start your journey into Big Data with the Oracle Academy today!

    - by KLaker
     Big Data has the power to change the way we work, live, and think. The datafication of everything will create unprecedented demand for data scientists, software developers and engineers who can derive value from unstructured data to transform the world. The Oracle Academy Big Data Resource Guide is a collection of articles, videos, and other resources organized to help you gain a deeper understanding of the exciting field of Big Data. To start your journey visit the Oracle Academy website here: https://academy.oracle.com/oa-web-big-data.html. This landing pad will guide through the whole area of big data using the following structure: What is “Big Data” Engineered Systems Integration Database and Data Analytics Advanced Information Supplemental Information This is great resource packed with must-see videos and must-read whitepapers and blog posts by industry leaders.  Enjoy Technorati Tags: Big Data, Data Warehousing, Oracle, Training

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  • Moving large amounts of data between shared hosts

    - by Bryan M.
    I recently acquired a client who is a photographer and was interested in moving web hosts since his current host had threatened to throw him off due to CPU spiking. The migration went fairly easily, with about 350MBs of website and media files. Then I discovered about 60GBs of client galleries he had failed to mention. I am unable to move this much data myself, since I'm capping out at about 20kb/s on the FTP connection. Has anyone encountered a situation where they needed to migrate this much data between cheap hosting? Should we contact the hosting companies about this (he is moving from Westhost to MediaTemple)?

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  • Data Warehouse Workshop

    - by Davide Mauri
    I’m really really pleased to announce that it’s possible to register to the Data Warehouse Workshop that I and Thomas Kejser developed togheter.  Several months ago we decided to join forces in order to create a workshop that would contain not only the theoretical stuff, but also the experience we both have and all the best practices and lesson learned that can make the difference between a success and a failure when building a Data Warehouse. The first sheduled date is 7 February in Kista (Sweden): http://www.eventzilla.net/web/event?eventid=2138965081 and until 30th November there is the Super Early Bird to save more the 100€ (150$). The workshop will be very similar to the one I delivered at PASS Summit summit, with some extra technical stuff since it’s one hour longer. In addition to that for this first version both me and Thomas will be present, so it’s a great change  to make sure you super-charge your DW/BI project with insights that aren’t available anywhere else! If you’re into the BI field and you live in Europe, don’t miss this opportunity!

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  • What do I need to know about Data Structures and Algorithms in the "real" world

    - by Ray T Champion
    I just finished the data structures and algorithms course in school , I took it during the summer so 6wks course vs a 16 wk course during the regular semester. So not only was the course hard but it was really really really fast. My question is what do I need to know about data structures in the real world? I understand what they do and how they work, for the most part, but I had a real tough time coding them , I wouldn't be able to write the code for a binary tree class or a balanced tree class from scratch .... Is that bad? should I retake it , or is knowledge of how they work sufficient, without being able to write the classes from scratch?

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  • Coherence Data Guarantees for Data Reads - Basic Terminology

    - by jpurdy
    When integrating Coherence into applications, each application has its own set of requirements with respect to data integrity guarantees. Developers often describe these requirements using expressions like "avoiding dirty reads" or "making sure that updates are transactional", but we often find that even in a small group of people, there may be a wide range of opinions as to what these terms mean. This may simply be due to a lack of familiarity, but given that Coherence sits at an intersection of several (mostly) unrelated fields, it may be a matter of conflicting vocabularies (e.g. "consistency" is similar but different in transaction processing versus multi-threaded programming). Since almost all data read consistency issues are related to the concept of concurrency, it is helpful to start with a definition of that, or rather what it means for two operations to be concurrent. Rather than implying that they occur "at the same time", concurrency is a slightly weaker statement -- it simply means that it can't be proven that one event precedes (or follows) the other. As an example, in a Coherence application, if two client members mutate two different cache entries sitting on two different cache servers at roughly the same time, it is likely that one update will precede the other by a significant amount of time (say 0.1ms). However, since there is no guarantee that all four members have their clocks perfectly synchronized, and there is no way to precisely measure the time it takes to send a given message between any two members (that have differing clocks), we consider these to be concurrent operations since we can not (easily) prove otherwise. So this leads to a question that we hear quite frequently: "Are the contents of the near cache always synchronized with the underlying distributed cache?". It's easy to see that if an update on a cache server results in a message being sent to each near cache, and then that near cache being updated that there is a window where the contents are different. However, this is irrelevant, since even if the application reads directly from the distributed cache, another thread update the cache before the read is returned to the application. Even if no other member modifies a cache entry prior to the local near cache entry being updated (and subsequently read), the purpose of reading a cache entry is to do something with the result, usually either displaying for consumption by a human, or by updating the entry based on the current state of the entry. In the former case, it's clear that if the data is updated faster than a human can perceive, then there is no problem (and in many cases this can be relaxed even further). For the latter case, the application must assume that the value might potentially be updated before it has a chance to update it. This almost aways the case with read-only caches, and the solution is the traditional optimistic transaction pattern, which requires the application to explicitly state what assumptions it made about the old value of the cache entry. If the application doesn't want to bother stating those assumptions, it is free to lock the cache entry prior to reading it, ensuring that no other threads will mutate the entry, a pessimistic approach. The optimistic approach relies on what is sometimes called a "fuzzy read". In other words, the application assumes that the read should be correct, but it also acknowledges that it might not be. (I use the qualifier "sometimes" because in some writings, "fuzzy read" indicates the situation where the application actually sees an original value and then later sees an updated value within the same transaction -- however, both definitions are roughly equivalent from an application design perspective). If the read is not correct it is called a "stale read". Going back to the definition of concurrency, it may seem difficult to precisely define a stale read, but the practical way of detecting a stale read is that is will cause the encompassing transaction to roll back if it tries to update that value. The pessimistic approach relies on a "coherent read", a guarantee that the value returned is not only the same as the primary copy of that value, but also that it will remain that way. In most cases this can be used interchangeably with "repeatable read" (though that term has additional implications when used in the context of a database system). In none of cases above is it possible for the application to perform a "dirty read". A dirty read occurs when the application reads a piece of data that was never committed. In practice the only way this can occur is with multi-phase updates such as transactions, where a value may be temporarily update but then withdrawn when a transaction is rolled back. If another thread sees that value prior to the rollback, it is a dirty read. If an application uses optimistic transactions, dirty reads will merely result in a lack of forward progress (this is actually one of the main risks of dirty reads -- they can be chained and potentially cause cascading rollbacks). The concepts of dirty reads, fuzzy reads, stale reads and coherent reads are able to describe the vast majority of requirements that we see in the field. However, the important thing is to define the terms used to define requirements. A quick web search for each of the terms in this article will show multiple meanings, so I've selected what are generally the most common variations, but it never hurts to state each definition explicitly if they are critical to the success of a project (many applications have sufficiently loose requirements that precise terminology can be avoided).

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  • Can data classes contain methods for validation?

    - by Arturas M
    OK, say I have a data class for a user: public class User { private String firstName; private String lastName; private long personCode; private Date birthDate; private Gender gender; private String email; private String password; Now let's say I want to validate email, whether names are not empty, whether birth date is in normal range, etc. Can I put that validation method in this class together with data? Or should it be in UserManager which in my case handles the lists of these users?

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  • How much data validation is too much? [closed]

    - by adbertram
    Possible Duplicate: Data input validation - Where? How much? I'm a new PHP developer and am into Powershell quite a bit but this question is language agnostic. I've been questioning my code quite a bit lately thinking about how many nets I should setup to catch exceptions, verify results, etc. I realize that I could go crazy trying to verify each and every line of code but at the same time I want the code as resilient as possible. I'm not talking about user input but verifying output from methods. Is there some standard or rule of thumb to go by when deciding when and where to do data validation?

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  • Data structure for file search

    - by poly
    I've asked this question before and I got a few answers/idea, but I'm not sure how to implement them. I'm building a telecom messaging solution. Currently, I'm using a database to save my transaction/messages for the network stack I've built, and as you know it's slower than using a data structure (hash, linkedlist, etc...). My problem is that the data can be really huge, and it won't fit in the memory. I was thinking of saving the records in a file and the a key and line number in a hash, then if I want to access some record then I can get the line number from the hash, and get it from the file. I don't know how efficient is this; I think the database is doing a way better job than this on my behalf. Please share whatever you have in mind.

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  • What is the difference between type and type.__new__ in python?

    - by Jason Baker
    I was writing a metaclass and accidentally did it like this: class MetaCls(type): def __new__(cls, name, bases, dict): return type(name, bases, dict) ...instead of like this: class MetaCls(type): def __new__(cls, name, bases, dict): return type.__new__(cls, name, bases, dict) What exactly is the difference between these two metaclasses? And more specifically, what caused the first one to not work properly (some classes weren't called into by the metaclass)?

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  • FORTRAN: determine variable type

    - by tibbs
    hello, GOOGLE has yet to find an answer for me, so here goes: In FORTRAN, is there a way to determine the TYPE of a variable? E.G., pass the variable type as an argument in a function, to then be able to call type-specific code with that fuction; eliminating the need to have seperate similar functions for each data type. thanks.

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