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  • SSIS Design Pattern: Loading Variable-Length Rows

    - by andyleonard
    Introduction I encounter flat file sources with variable-length rows on occassion. Here, I supply one SSIS Design Pattern for loading them. What's a Variable-Length Row Flat File? Great question - let's start with a definition. A variable-length row flat file is a text source of some flavor - comma-separated values (CSV), tab-delimited file (TDF), or even fixed-length, positional-, or ordinal-based (where the location of the data on the row defines its field). The major difference between a "normal"...(read more)

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  • Ocaml Pattern Matching

    - by Atticus
    Hey guys, I'm pretty new to OCaml and pattern matching, so I was having a hard time trying to figure this out. Say that I have a list of tuples. What I want to do is match a parameter with one of the tuples based on the first element in the tuple, and upon doing so, I want to return the second element of the tuple. So for example, I want to do something like this: let list = [ "a", 1; "b", 2"; "c", 3; "d", 4 ] ;; let map_left_to_right e rules = match e with | first -> second | first -> second | first -> second If I use map_left_to_right "b" list, I want to get 2 in return. I therefore want to list out all first elements in the list of rules and match the parameter with one of these elements, but I am not sure how to do so. I was thinking that I need to use either List.iter or List.for_all to do something like this. Any help would be appreciated. Thanks!

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  • Parametrized Strategy Pattern

    - by ott
    I have several Java classes which implement the strategy pattern. Each class has variable number parameters of different types: interface Strategy { public data execute(data); } class StrategyA implements Strategy { public data execute(data); } class StrategyB implements Strategy { public StrategyB(int paramA, int paramB); public data execute(data); } class StrategyB implements Strategy { public StrategyB(int paramA, String paramB, double paramC); public data execute(data); } Now I want that the user can enter the parameters in some kind of UI. The UI should be chosen at runtime, i.e. the strategies should be independent of it. The parameter dialog should not be monolithic and there should be the possibility to make it behave and look different for each strategy and UI (e.g. console or Swing). How would you solve this problem?

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  • Combining template method with strategy

    - by Mekswoll
    An assignment in my software engineering class is to design an application which can play different forms a particular game. The game in question is Mancala, some of these games are called Wari or Kalah. These games differ in some aspects but for my question it's only important to know that the games could differ in the following: The way in which the result of a move is handled The way in which the end of the game is determined The way in which the winner is determined The first thing that came to my mind to design this was to use the strategy pattern, I have a variation in algorithms (the actual rules of the game). The design could look like this: I then thought to myself that in the game of Mancala and Wari the way the winner is determined is exactly the same and the code would be duplicated. I don't think this is by definition a violation of the 'one rule, one place' or DRY principle seeing as a change in rules for Mancala wouldn't automatically mean that rule should be changed in Wari as well. Nevertheless from the feedback I got from my professor I got the impression to find a different design. I then came up with this: Each game (Mancala, Wari, Kalah, ...) would just have attribute of the type of each rule's interface, i.e. WinnerDeterminer and if there's a Mancala 2.0 version which is the same as Mancala 1.0 except for how the winner is determined it can just use the Mancala versions. I think the implementation of these rules as a strategy pattern is certainly valid. But the real problem comes when I want to design it further. In reading about the template method pattern I immediately thought it could be applied to this problem. The actions that are done when a user makes a move are always the same, and in the same order, namely: deposit stones in holes (this is the same for all games, so would be implemented in the template method itself) determine the result of the move determine if the game has finished because of the previous move if the game has finished, determine who has won Those three last steps are all in my strategy pattern described above. I'm having a lot of trouble combining these two. One possible solution I found would be to abandon the strategy pattern and do the following: I don't really see the design difference between the strategy pattern and this? But I am certain I need to use a template method (although I was just as sure about having to use a strategy pattern). I also can't determine who would be responsible for creating the TurnTemplate object, whereas with the strategy pattern I feel I have families of objects (the three rules) which I could easily create using an abstract factory pattern. I would then have a MancalaRuleFactory, WariRuleFactory, etc. and they would create the correct instances of the rules and hand me back a RuleSet object. Let's say that I use the strategy + abstract factory pattern and I have a RuleSet object which has algorithms for the three rules in it. The only way I feel I can still use the template method pattern with this is to pass this RuleSet object to my TurnTemplate. The 'problem' that then surfaces is that I would never need my concrete implementations of the TurnTemplate, these classes would become obsolete. In my protected methods in the TurnTemplate I could just call ruleSet.determineWinner(). As a consequence, the TurnTemplate class would no longer be abstract but would have to become concrete, is it then still a template method pattern? To summarize, am I thinking in the right way or am I missing something easy? If I'm on the right track, how do I combine a strategy pattern and a template method pattern? This is part of a homework assignment but I'm not looking to be gifted the answer, I have deliberately been very verbose in my question to show that I have thought about it before coming here to ask a question

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  • Is there a design pattern for chained observers?

    - by sharakan
    Several times, I've found myself in a situation where I want to add functionality to an existing Observer-Observable relationship. For example, let's say I have an Observable class called PriceFeed, instances of which are created by a variety of PriceSources. Observers on this are notified whenever the underlying PriceSource updates the PriceFeed with a new price. Now I want to add a feature that allows a (temporary) override to be set on the PriceFeed. The PriceSource should still update prices on the PriceFeed, but for as long as the override is set, whenever a consumer asks PriceFeed for it's current value, it should get the override. The way I did this was to introduce a new OverrideablePriceFeed that is itself both an Observer and an Observable, and that decorates the actual PriceFeed. It's implementation of .getPrice() is straight from Chain of Responsibility, but how about the handling of Observable events? When an override is set or cleared, it should issue it's own event to Observers, as well as forwarding events from the underlying PriceFeed. I think of this as some kind of a chained observer, and was curious if there's a more definitive description of a similar pattern.

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  • Identity Map Pattern and the Entity Framework

    - by nikolaosk
    This is going to be the seventh post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here and the third one here , the fourth one here , the fifth one here and the sixth one here . I have a post regarding ASP.Net and EntityDataSource. You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here , here and here . In...(read more)

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  • Optimal communication pattern to update subscribers

    - by hpc
    What is the optimal way to update the subscriber's local model on changes C on a central model M? ( M + C - M_c) The update can be done by the following methods: Publish the updated model M_c to all subscribers. Drawback: if the model is big in contrast to the change it results in much more data to be communicated. Publish change C to all subscribes. The subscribers will then update their local model in the same way as the server does. Drawback: The client needs to know the business logic to update the model in the same way as the server. It must be assured that the subscribed model stays equal to the central model. Calculate the delta (or patch) of the change (M_c - M = D_c) and transfer the delta. Drawback: This requires that calculating and applying the delta (M + D_c = M_c) is an cheap/easy operation. If a client newly subscribes it must be initialized. This involves sending the current model M. So method 1 is always required. Think of playing chess as a concrete example: Subscribers send moves and want to see the latest chess board state. The server checks validity of the move and applies it to the chess board. The server can then send the updated chessboard (method 1) or just send the move (method 2) or send the delta (method 3): remove piece on field D4, put tower on field D8.

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  • Kill a tree, save your website? Content strategy in action, part III

    - by Roger Hart
    A lot has been written about how driving content strategy from within an organisation is hard. And that's true. Red Gate is pretty receptive to new ideas, so although I've not had a total walk in the park, it's been a hike with charming scenery. But I'm one of the lucky ones. Lots of people are involved in content, and depending on your organisation some of those people might be the kind who'll gleefully call themselves "stakeholders". People holding a stake generally want to stick it through something's heart and bury it at a crossroads. Winning them over is not always easy. (Richard Ingram has made a nice visual summary of how this can feel - Content strategy Snakes & ladders - pdf ) So yes, a lot of content strategy advocates are having a hard time. And sure, we've got a nice opportunity to get together and have a hug and a cry, but in the interim we could use a hand. What to do? My preferred approach is, I'll confess, brutal. I'd like nothing so much as to take a scorched earth approach to our website. Burn it, salt the ground, and build the new one right: focusing on clearly delineated business and user content goals, and instrumented so we can tell if we're doing it right. I'm never getting buy-in for that, but a boy can dream. So how about just getting buy-in for some small, tenable improvements? Easier, but still non-trivial. I sat down for a chat with our marketing and design guys. It seemed like a good place to start, even if they weren't up for my "Ctrl-A + Delete"  solution. We talked through some of this stuff, and we pretty much agreed that our content is a bit more broken than we'd ideally like. But to get everybody on board, the problems needed visibility. Doing a visual content inventory Print out the internet. Make a Wall Of Content. Seriously. If you've already done a content inventory, you know your architecture, and you know the scale of the problem. But it's quite likely that very few other people do. So make it big and visual. I'm going to carbon hell, but it seems to be working. This morning, I printed out a tiny, tiny part of our website: the non-support content pertaining to SQL Compare I made big, visual, A3 blowups of each page, and covered a wall with them. A page per web page, spread over something like 6M x 2M, with metrics, right in front of people. Even if nobody reads it (and they are doing) the sheer scale is shocking. 53 pages, all told. Some are redundant, some outdated, some trivial, a few fantastic, and frighteningly many that are great ideas delivered not-quite-right. You have to stand quite far away to get it all in your field of vision. For a lot of today, a whole bunch of folks have been gawping in amazement, talking each other through it, peering at the details, and generally getting excited about content. Developers, sales guys, our CEO, the marketing folks - they're engaged. Will it last? I make no promises. But this sort of wave of interest is vital to getting a content strategy project kicked off. While the content strategist is a saucer-eyed orphan in the cupboard under the stairs, they're not getting a whole lot done. Of course, just printing the site won't necessarily cut it. You have to know your content, and be able to talk about it. Ideally, you'll also have page view and time-on-page metrics. One of the most powerful things you can do is, when people are staring at your wall of content, ask them what they think half of it is for. Pretty soon, you've made a case for content strategy. We're also going to get folks to mark it up - cover it with notes and post-its, let us know how they feel about our content. I'll be blogging about how that goes, but it's exciting. Different business functions have different needs from content, so the more exposure the content gets, and the more feedback, the more you know about those needs. Fingers crossed for awesome.

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  • Managing Strategy objects with Hibernate & Spring

    - by Francois
    This is a design question better explained with a Stack Overflow analogy: Users can earn Badges. Users, Badges and Earned Badges are stored in the database. A Badge’s logic is run by a Badge Condition Strategy. I would prefer not to have to store Badge Condition Strategies in the database, because they are complex tree structure objects. How do I associate a Badge stored in the database with its Badge Condition Strategy? I can only think of workaround solutions. For example: create 1 class per badge and use a SINGLE_TABLE inheritance strategy. Or get the badge from the database, and then programmatically lookup and inject the correct Badge Condition Strategy. Thanks for suggesting a better design.

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  • Is MVC a Design Pattern or Architectural pattern

    - by JCasso
    According to Sun and Msdn it is a design pattern. According to Wikipedia it is an architectural pattern In comparison to design patterns, architectural patterns are larger in scale. (Wikipedia - Architectural pattern) Or it is an architectural pattern that also has a design pattern ? Which one is true ?

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  • Query Object Pattern (Design Pattern)

    - by The Elite Gentleman
    Hi Guys, I need to implement a Query Object Pattern in Java for my customizable search interface (of a webapp I'm writing). Does anybody know where I can get an example/tutorial of Query Object Pattern (Martin Fowler's QoP)? Thanks in Advance ADDITION How to add a Query Pattern to an existing DAO pattern?

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  • Java RegEx Pattern not matching (works in .NET)

    - by CDSO1
    Below is an example that is producing an exception in Java (and not matching the input). Perhaps I misunderstood the JavaDoc, but it looks like it should work. Using the same pattern and input in C# will produce a match. import java.util.regex.Matcher; import java.util.regex.Pattern; public class Main { public static void main(String[] args) { String pattern = "aspx\\?uid=([^']*)"; Pattern p = Pattern.compile(pattern); Matcher m = p.matcher("id='page.aspx?uid=123'"); System.out.println(m.groupCount() > 0 ? m.group(1) : "No Matches"); } }

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  • How should I handle "real time" events in an online strategy game?

    - by Hojat Taheri
    Some online strategy games have real time events. For example when you send troops to attack somewhere, the attack happens at the right time in the future. Checking the database again and again to get the list of attacks happening each second would cause heavy load. Is there any technique to achieve this goal? Another example: You want to attack a village 3 hours away, you send troops and the attack occurs 3 hours later. Should there be an script to check the database at each second to run the query at the specified time?

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  • Can you point me to a nontrivial strategy pattern implementation?

    - by Eugen Martynov
    We are faced implementing a registration workflow with many branches. There are three main flows which in some conditions lead to one another. Each flow has at least four different steps; some steps interact with the server, and every step adds more information to the state. Also the requirement is to have it persistent between sessions, so if the user closes the app (this is a mobile app), it will restore the process from the last completed step with the state from the previous session. I think this could benefit from the use of the strategy pattern, but I've never had to implement it for such a complex case. Does anyone know of any examples in open source or articles from which I could find inspiration? Preferably the examples would be from a live/working/stable application. I'm interested in Java implementation mostly; we are developing for Java mobile phones: android, blackberry and J2ME. We have an SDK which is quite well separated from platform specific implementations, but examples in C++, C#, Objective-C or Python would be acceptable.

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  • Using the Specification Pattern

    - by Kane
    Like any design pattern the Specification Pattern is a great concept but susceptible to overuse by an eager architect/developer. I am about to commence development on a new application (.NET & C#) and really like the concept of the Specification Pattern and am keen to make full use of it. However before I go in all guns blazing I would be really interested in knowing if anyone could share the pain points that experienced when use the Specification Pattern in developing an application. Ideally I'm looking to see if others have had issues in Writing unit tests against the specification pattern Deciding which layer the specifications should live in (Repository, Service, Domain, etc) Using it everywhere when a simple if statement would have done the job etc? Thanks in advance

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  • Is component-based design an architectural pattern or design pattern?

    - by xEnOn
    When using the component-based paradigm in game development with engines like Unity, is component-based design an architectural pattern, or a design pattern? Can I even say that component-based design is my "main" architectural pattern for my game? I see architectural patterns as being more high-level than design pattern. The component-based design in game development's context (like with Unity engine) seems to fit as an architectural pattern to me. However, on some sites, I read that component-based design is a behavioural pattern, much like other behavioural design patterns, and not so much like an architectural pattern like MVC.

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  • Best strategy for synching data in iPhone app

    - by iamj4de
    I am working on a regular iPhone app which pulls data from a server (XML, JSON, etc...), and I'm wondering what is the best way to implement synching data. Criteria are speed (less network data exchange), robustness (data recovery in case update fails), offline access and flexibility (adaptable when the structure of the database changes slightly, like a new column). I know it varies from app to app, but can you guys share some of your strategy/experience? For me, I'm thinking of something like this: 1) Store Last Modified Date in iPhone 2) Upon launching, send a message like getNewData.php?lastModifiedDate=... 3) Server will process and send back only modified data from last time. 4) This data is formatted as so: <+><data id="..."></data></+> // add this to SQLite/CoreData <-><data id="..."></data></-> // remove this <%><data id="..."><attribute>newValue</attribute></data></%> // new modified value I don't want to make <+, <-, <%... for each attribute as well, because it would be too complicated, so probably when receive a <% field, I would just remove the data with the specified id and then add it again (assuming id here is not some automatically auto-incremented field). 5) Once everything is downloaded and updated, I will update the Last Modified Date field. The main problem with this strategy is: If the network goes down when I am updating something = the Last Modified Date is not yet updated = next time I relaunch the app, I will have to go through the same thing again. Not to mention potential inconsistent data. If I use a temporary table for update and make the whole thing atomic, it would work, but then again, if the update is too long (lots of data change), the user has to wait a long time until new data is available. Should I use Last-Modified-Date for each of the data field and update data gradually?

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  • F# Active Pattern List.filter or equivalent

    - by akaphenom
    I have a records of types type tradeLeg = { id : int ; tradeId : int ; legActivity : LegActivityType ; actedOn : DateTime ; estimates : legComponents ; entryType : ShareOrDollarBased ; confirmedPrice: DollarsPerShare option; actuals : legComponents option ; type trade = { id : int ; securityId : int ; ricCode : string ; tradeActivity : TradeType ; enteredOn : DateTime ; closedOn : DateTime ; tradeLegs : tradeLeg list ; } Obviously the tradeLegs are a type off of a trade. A leg may be settled or unsettled (or unsettled but price confirmed) - thus I have defined the active pattern: let (|LegIsSettled|LegIsConfirmed|LegIsUnsettled|) (l: tradeLeg) = if Helper.exists l.actuals then LegIsSettled elif Helper.exists l.confirmedPrice then LegIsConfirmed else LegIsUnsettled and then to determine if a trade is settled (based on all legs matching LegIsSettled pattern: let (|TradeIsSettled|TradeIsUnsettled|) (t: trade) = if List.exists ( fun l -> match l with | LegIsSettled -> false | _ -> true) t.tradeLegs then TradeIsSettled else TradeIsUnsettled I can see some advantages of this use of active patterns, however i would think there is a more efficient way to see if any item of a list either matches (or doesn't) an actie pattern without having to write a lambda expression specifically for it, and using List.exist. Question is two fold: is there a more concise way to express this? is there a way to abstract the functionality / expression (fun l - match l with | LegIsSettled - false | _ - true) Such that let itemMatchesPattern pattern item = match item with | pattern -> true | _ -> false such I could write (as I am reusing this design-pattern): let curriedItemMatchesPattern = itemMatchesPattern LegIsSettled if List.exists curriedItemMatchesPattern t.tradeLegs then TradeIsSettled else TradeIsUnsettled Thoughts?

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  • Print a string that contains a certain pattern in Java

    - by jjpotter
    I am trying to find a regular expression within a line of a .csv file, so I can eventually save all the matches to another file, and lose all the other junk. So a line in my file might look like: MachineName,User,IP,VariableData,Location The VariableData is what I want to match, and if there's a match, print the line. I am using a pattern for this because I only want 3 out of 10 of variations of VariableData, and out of those 3, they are numbered differently(example, "pc104, pccrt102, pccart65"). I am trying to do this using the Scanner Class and keeping it simple as possible so I can understand it. Here is where I was heading with this...(the pattern isn't complete, just have it like this for testing). import java.io.File; import java.util.Scanner; import java.util.regex.Pattern; public class pcv { public static void main(String[] args) { File myFile = new File("c:\\temp\\report.csv"); Pattern myPat = Pattern.compile("pc"); try{ Scanner myScan = new Scanner(myFile); while(myScan.hasNext()){ if(myScan.hasNext(myPat)){ System.out.println("Test"); } } }catch(Exception e){ } } } This code loops, im guessing the .hasNext() methods are resetting themselves. I've played around with the Matcher class a little bit, but only found a way to match the expression but not get the whole line. My other throught was maybe somehow count the line that contains the pattern, then go back and print the line that corresponds to the counts.

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  • Understanding branching strategy/workflow correctly

    - by burnersk
    I'm using svn without branches (trunk-only) for a very long time at my workplace. I had discovered most or all of the issues related to projects which do not have any branching strategy. Unlikely this is not going to change at my workplace but for my private projects. For my private projects which most includes coworkers and working together at the same time on different features I like to have an robust branching strategy with supports long-term releases powered by git. I find out that the Atlassian Toolchain (JIRA, Stash and Bamboo) helped me most and it also recommending me an branching strategy which I like to verify for the team needs. The branching strategy was taken directly from Atlassian Stash recommendation with a small modification to the hotfix branch tree. All hotfixes should also merged into mainline. The branching strategy in words mainline (also known as master with git or trunk with svn) contains the "state of the art" developing release. Everything here was successfully checked with various automated tests (through Bamboo) and looks like everything is working. It is not proven as working because of possible missing tests. It is ready to use but not recommended for production. feature covers all new features which are not completely finished. Once a feature is finished it will be merged into mainline. Sample branch: feature/ISSUE-2-A-nice-Feature bugfix fixes non-critical bugs which can wait for the next normal release. Sample branch: bugfix/ISSUE-1-Some-typos production owns the latest release. hotfix fixes critical bugs which have to be release urgent to mainline, production and all affected long-term *release*es. Sample branch: hotfix/ISSUE-3-Check-your-math release is for long-term maintenance. Sample branches: release/1.0, release/1.1 release/1.0-rc1 I am not an expert so please provide me feedback. Which problems might appear? Which parts are missing or slowing down the productivity?

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  • Test Strategy for Addins

    - by Amit
    I was wondering if someone from the forum, can help me in uderstanding the type of Testing that will be performed, I mean a Test Strategy, we need to test things like Add-ins. Also need to know how can I reply to the person who has replied to my question, I kow its a bit not so mature quesiton, but if someone can explain. Regards Amit

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  • git strategy to have a set of commits limited to a particular branch

    - by becomingGuru
    I need to merge between dev and master frequently. I also have a commit that I need to apply to dev only, for things to work locally. Earlier I only merged from dev to master, so I had a branch production_changes that contained the "undo commit" of the dev special commit. and from the master, I merged this. Used to work fine. Now each time I merge from dev to master and vice versa, I am having to cherry-pick and apply the same commit again and again :(. Which is UGLY. What strategy can I adapt so that I can seamlessly merge between 2 branches, yet retain some of the changes only on one of those branches?

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  • OLL Live webcast - Using SQL for Pattern Matching in Oracle Database

    - by KLaker
    If you are interested in learning about our exciting new 12c SQL pattern matching feature then mark your diaries. On Wednesday, October 30th at 8:00 am (US/Pacific time zone) Supriya Ananth, who is one of our top curriculum developers at Oracle, will be hosting an OLL webcast on our new SQL pattern matching feature. The ability to recognize patterns in a sequence of rows has been a capability that was widely desired, but not possible with SQL until now. Row pattern matching in native SQL improves application and development productivity and query efficiency for row-sequence analysis. With Oracle Database 12c you can use the new MATCH_RECOGNIZE clause to perform pattern matching in SQL to do the following: Logically partition and order the data using the PARTITION BY and ORDER BY clauses Use regular expressions syntax to define patterns of rows to seek using the PATTERN clause. These patterns a powerful and expressive feature, applied to the pattern variables you define. Specify the logical conditions required to map a row to a row pattern variable in the DEFINE clause. Define measures, which are expressions usable in the MEASURES clause of the SQL query. For more information and to register for this exciting webcast please visit the OLL Live website, see here: https://apex.oracle.com/pls/apex/f?p=44785:145:116820049307135::::P145_EVENT_ID,P145_PREV_PAGE:461,143.  Please note - if the above link does not work then go to OLL (https://apex.oracle.com/pls/apex/f?p=44785:1:) and click the OLL Live icon (upper right, beneath the Login link or logout link if you are already logged in). The pattern matching webcast is listed on the calendar of events on 30 October.

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  • Web crawler update strategy

    - by superb
    I want to crawl useful resource (like background picture .. ) from certain websites. It is not a hard job, especially with the help of some wonderful projects like scrapy. The problem here is I not only just want crawl this site ONE TIME. I also want to keep my crawl long running and crawl the updated resource. So I want to know is there any good strategy for a web crawler to get updated pages? Here's a coarse algorithm I've thought of. I divided the crawl process into rounds. Each round URL repository will give crawler a certain number (like , 10000) of URLs to crawl. And then next round. The detailed steps are: crawler add start URLs to URL repository crawler ask URL repository for at most N URL to crawl crawler fetch the URLs, and update certain information in URL repository, like the page content, the fetch time and whether the content has been changed. just go back to step 2 To further specify that, I still need to solve following question: How to decide the "refresh-ness" of a web page, which indicates the probability that this web page has been updated ? Since that is an open question, hopefully it will brought some fruitful discussion here.

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