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  • Object desing problem for simple school application

    - by Aragornx
    I want to create simple school application that provides grades,notes,presence,etc. for students,teachers and parents. I'm trying to design objects for this problem and I'm little bit confused - because I'm not very experienced in class designing. Some of my present objects are : class PersonalData() { private String name; private String surename; private Calendar dateOfBirth; [...] } class Person { private PersonalData personalData; } class User extends Person { private String login; private char[] password; } class Student extends Person { private ArrayList<Counselor> counselors = new ArrayList<>(); } class Counselor extends Person { private ArrayList<Student> children = new ArrayList<>(); } class Teacher extends Person { private ArrayList<ChoolClass> schoolClasses = new ArrayList<>(); private ArrayList<Subject> subjects = new ArrayList<>(); } This is of course a general idea. But I'm sure it's not the best way. For example I want that one person could be a Teacher and also a Parent(Counselor) and present approach makes me to have two Person objects. I want that user after successful logging in get all roles that it has (Student or Teacher or (Teacher & Parent) ). I think I should make and use some interfaces but I'm not sure how to do this right. Maybe like this: interface Role { } interface TeacherRole implements Role { void addGrade( Student student, Grade grade, [...] ); } class Teacher implements TeacherRole { private Person person; [...] } class User extends Person{ ArrayList<Role> roles = new ArrayList<>(); } Please if anyone could help me to make this right or maybe just point me to some literature/article that covers practical objects design.

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  • Need some help understanding this problem about maximizing graph connectivity

    - by Legend
    I was wondering if someone could help me understand this problem. I prepared a small diagram because it is much easier to explain it visually. Problem I am trying to solve: 1. Constructing the dependency graph Given the connectivity of the graph and a metric that determines how well a node depends on the other, order the dependencies. For instance, I could put in a few rules saying that node 3 depends on node 4 node 2 depends on node 3 node 3 depends on node 5 But because the final rule is not "valuable" (again based on the same metric), I will not add the rule to my system. 2. Execute the request order Once I built a dependency graph, execute the list in an order that maximizes the final connectivity. I am not sure if this is a really a problem but I somehow have a feeling that there might exist more than one order in which case, it is required to choose the best order. First and foremost, I am wondering if I constructed the problem correctly and if I should be aware of any corner cases. Secondly, is there a closely related algorithm that I can look at? Currently, I am thinking of something like Feedback Arc Set or the Secretary Problem but I am a little confused at the moment. Any suggestions? PS: I am a little confused about the problem myself so please don't flame on me for that. If any clarifications are needed, I will try to update the question.

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  • Shortest acyclic path on directed cyclic graph with negative weights/cycles

    - by Janathan
    I have a directed graph which has cycles. All edges are weighted, and the weights can be negative. There can be negative cycles. I want to find a path from s to t, which minimizes the total weight on the path. Sure, it can go to negative infinity when negative cycles exist. But what if I disallow cycles in the path (not in the original graph)? That is, once the path leaves a node, it can not enter the node again. This surely avoids the negative infinity problem, but surprisingly no known algorithm is found by a search on Google. The closest is Floyd–Warshall algorithm, but it does not allow negative cycles. Thanks a lot in advance. Edit: I may have generalized my original problem too much. Indeed, I am given a cyclic directed graph with nonnegative edge weights. But in addition, each node has a positive reward too. I want to find a simple path which minimizes (sum of edge weights on the path) - (sum of node rewards covered by the path). This can be surely converted to the question that I posted, but some structure is lost. And some hint from submodular analysis suggests this motivating problem is not NP-hard. Thanks a lot

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  • Unable to retrieve search results from server side : Facebook Graph API usig Python

    - by DjangoRocks
    Hi all, I'm doing some simple Python + FB Graph training on my own, and I faced a weird problem: import time import sys import urllib2 import urllib from json import loads base_url = "https://graph.facebook.com/search?q=" post_id = None post_type = None user_id = None message = None created_time = None def doit(hour): page = 1 search_term = "\"Plastic Planet\"" encoded_search_term = urllib.quote(search_term) print encoded_search_term type="&type=post" url = "%s%s%s" % (base_url,encoded_search_term,type) print url while(1): try: response = urllib2.urlopen(url) except urllib2.HTTPError, e: print e finally: pass content = response.read() content = loads(content) print "==================================" for c in content["data"]: print c print "****************************************" try: content["paging"] print "current URL" print url print "next page!------------" url = content["paging"]["next"] print url except: pass finally: pass """ print "new URL is =======================" print url print "==================================" """ print url What I'm trying to do here is to automatically page through the search results, but trying for content["paging"]["next"] But the weird thing is that no data is returned; i received the following: {"data":[]} Even in the very first loop. But when i copied the URL into a browser, a lot of results were returned. I've also tried a version with my access token and th same thing happens. Can anyone enlighten me? +++++++++++++++++++EDITED and SIMPLIFIED++++++++++++++++++ ok thanks to TryPyPy, here's the simplified and edited version of my previous question: Why is that: import urllib2 url = "https://graph.facebook.com/searchq=%22Plastic+Planet%22&type=post&limit=25&until=2010-12-29T19%3A54%3A56%2B0000" response = urllib2.urlopen(url) print response.read() result in {"data":[]} ? But the same url produces a lot of data in a browser? Anyone? Best Regards.

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  • Safe way for getting/finding a vertex in a graph with custom properties -> good programming practice

    - by Shadow
    Hi, I am writing a Graph-class using boost-graph-library. I use custom vertex and edge properties and a map to store/find the vertices/edges for a given property. I'm satisfied with how it works, so far. However, I have a small problem, where I'm not sure how to solve it "nicely". The class provides a method Vertex getVertex(Vertexproperties v_prop) and a method bool hasVertex(Vertexproperties v_prop) The question now is, would you judge this as good programming practice in C++? My opinion is, that I have first to check if something is available before I can get it. So, before getting a vertex with a desired property, one has to check if hasVertex() would return true for those properties. However, I would like to make getVertex() a bit more robust. ATM it will segfault when one would directly call getVertex() without prior checking if the graph has a corresponding vertex. A first idea was to return a NULL-pointer or a pointer that points past the last stored vertex. For the latter, I haven't found out how to do this. But even with this "robust" version, one would have to check for correctness after getting a vertex or one would also run into a SegFault when dereferencing that vertex-pointer for example. Therefore I am wondering if it is "ok" to let getVertex() SegFault if one does not check for availability beforehand?

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  • SQL SERVER – Error: Fix – Msg 208 – Invalid object name ‘dbo.backupset’ – Invalid object name ‘dbo.backupfile’

    - by pinaldave
    Just a day before I got a very interesting email. Here is the email (modified a bit to make it relevant to this blog post). “Pinal, We are facing a very strange issue. One of our query  related to backup files and backup set has stopped working suddenly in SSMS. It works fine in application where we have and in the stored procedure but when we have it in our SSMS it gives following error. Msg 208, Level 16, State 1, Line 1 Invalid object name ‘dbo.backupfile’. Here are our queries which we are trying to execute. SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM dbo.backupset; SELECT logical_name, backup_size, file_type FROM dbo.backupfile; This query gives us details related to backupset and backup files when the backup was taken.” When I receive this kind of email, usually I have no answers directly. The claim that it works in stored procedure and in application but not in SSMS gives me no real data. I have requested him to very first check following two things: If he is connected to correct server? His answer was yes. If he has enough permissions? His answer was he was logged in as an admin. This means there was something more to it and I requested him to send me a screenshot of the his SSMS. He promptly sends that to me and as soon as I receive the screen shot I knew what was going on. Before I say anything take a look at the screenshot yourself and see if you can figure out why his queries are not working in SSMS. Just to make your life a bit easy, I have already given a hint in the image. The answer is very simple, the context of the database is master database. To execute above two queries the context of the database has to be msdb. Tables backupset and backupfile belong to the database msdb only. Here are two workaround or solution to above problem: 1) Change context to MSDB Above two queries when they will run as following they will not error out and will give the accurate desired result. USE msdb GO SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM dbo.backupset; SELECT logical_name, backup_size, file_type FROM dbo.backupfile; 2) Prefix the query with msdb There are cases above script used in stored procedure or part of big query, it is not possible to change the context of the whole query to any specific database. Use three part naming convention and prefix them with msdb. SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM msdb.dbo.backupset; SELECT logical_name, backup_size, file_type FROM msdb.dbo.backupfile; Very simple solution but sometime keeps people wondering for an answer. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Graph spacing algorithm

    - by David
    Hi, I am looking for an algorithm that would be useful for determining x y coordinates for a number objects to display on screen. Each object can be related to another object and there can be any number of relationships and there can be any number of these objects. There is no restriction on the overall size of area on which to display these object. I am writing this in php and would be looking to store the coordinates in an array.

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  • computing "node closure" of graph with removal

    - by Fakrudeen
    Given a directed graph, the goal is to combine the node with the nodes it is pointing to and come up with minimum number of these [lets give the name] super nodes. The catch is once you combine the nodes you can't use those nodes again. [first node as well as all the combined nodes - that is all the members of one super node] The greedy approach would be to pick the node with maximum out degree and combine that node with nodes it is pointing to and remove all of them. Do this every time with the nodes which are not removed yet from graph. The greedy is O(V), but this won't necessarily output minimum number super nodes. So what is the best algorithm to do this?

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  • Graph and permutation problem

    - by user319771
    I have a graph (with nodes and edges) containing symmetry and a group of permutations to label the nodes so no edges are changed (automorphisms). Now I would like to determine for which nodes a permutation exchanges two equivalent (i.e. nodes with the same color or symmetry class) neighboring nodes. When the nodes with equivalent neighbors stay the same, simply checking if the neighbors are exchanged in the permutation is enough. However, when the nodes with equivalent neighbors are also permuted (i.e. there are multiple nodes with the same color/symmetry class with the same equivalent neighbors), the problem becomes more complex. Is there any known algorithm for such a problem? Some remarks: The graph has no coordinates, it's a topology only

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  • Timeline graph - how to handle "time gaps"?

    - by ebae
    I've been working with Google chart API and annotated timeline. Drawing graphs is fine. I have no problem. However, I need to draw a timeline graph for share prices. And as you may know, share prices are meaningful only between certain times (e.g. from 10AM to 4PM, when the market opens and closes). How do I change the Google timeline graph so that on X-Axis, the range is from 10AM-4PM? Right now, it just draws a long constant line between 4PM till 10AM next day before prices start to move again. Man, I hope that makes sens. (Google finance chart seems to do it). Thank you SO much for whoever can answer. You are a CHAMPION!

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  • Boost graph libraries: setting edge weight values

    - by AndyUK
    I am investigating the use of the boost graph libraries in order to apply them to various network problems I have in mind. In the examples I have been looking at the graph edge values ("weights") are always initialized as integers, such as in these Bellman-Ford and Kruskal algorithms eg: int weights[] = { 1, 1, 2, 7, 3, 1, 1, 1 }; My problem is if I try and change the weights to double, I get a heap of warning messages about conversions etc, which so far I have not been able to figure out how to overcome. Does anyone see a way around this?

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  • Graph visualization code in javascript?

    - by Chris Farmer
    Hi. I have a data structure that represents a directed graph, and I want to render that dynamically on an HTML page. Does anyone know of any javascript code that can do a reasonable job with graph layout? These graphs will usually be just a few nodes, maybe ten at the very upper end, so my guess is that performance isn't going to be a big deal. Ideally, I'd like to be able to hook it in with jQuery so that users can tweak the layout manually by dragging the nodes around. Edit: Google's Visualization API seems to be more "graphs as charts" oriented than "graphs as nodes" oriented. I didn't see any node-oriented visualizations already built there, anyway. Do you know that one exists?

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  • Getting specific data from via facebook graph api

    - by Sima
    Hi, is there any possibility how to fetch any specific type of posts from facebook news feed via graph api?For example on my news feed I have statutuses, links, photos, vidoes, and so on..I only want to get the ones with type=status over graph api..I have seen some get parameters in documentation, but nothing like ?type=link..So I have tried /me/home?type=link, but unsurprisingly it have not worked:D So does anyone know how to do that?I can filter it in my PHP app, but then I need to get some further data..When I got 20 posts and only 10 would be statuses, I need to add the 10 remaiming? It is too possible, but I dont know how to do that:D Please help..!Thanks

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  • Facebook Graph - does the user "like" my page?

    - by Ican Zilb
    I am trying to upgrade my iPhone app to use the new facebook graph api. One thing I cannot find is how to find out if the current user connected from my app to facebook is a fan of my facebook page - (i.e. in the new paradigm - whether the user likes my page) In the Rest Api there was a function isFan, but not in the Graph. I can get all items the user likes and search whether one of them is my page, but certainly there must be an easier way instead of going trough thousands of records each time I must check whether he is a fan, right? If someone already figured it out how to do that from their new docs, I'll really appreciate if you share it with me.

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  • Facebook Open Graph Not Showing Object Title

    - by gregavola
    I'm having conflicting reports for our users that people that share Object Graph objects to their wall, are sometimes showing the Object title and other times not. Specifically, every test I do on my own account shows the Object Title, but on their Mobile apps - it doesn't appear. I've tested the Open Graph debugger.So I have a couple of questions: Is there a length limit on the number of characters? Does Facebook not show the whole Object.title on Mobile? Does Facebook scrap the OG tags and if it can't find them or if it timeout do they not receive them? Here is my sample OG url: https://untappd.com/user/gregavola/checkin/35486976 Response from FB: Post on my Wall: What can I do here? What am I missing?

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  • CSS Graph- Bars not showing correctly

    - by Olivia
    I'm trying to create a CSS/HTML based graph using this tutorial here. However instead of putting the data directly into the html code I'm importing it from a CSV file using PHP with the following code. <?PHP /* Open CSV file */ $handle = fopen("defects.csv", "r"); $c = 0; /* gets data from csv file */ while (($data = fgetcsv($handle, 1000, ",")) !== FALSE) { /* stores dates as variable $date */ $date[$c] = $data[0]; $c++; /* inserts defect data into html code */ echo "<dd class=\"p" . $data[2] . "\"><span><b>" . $data[2] . "</b></span></dd>"; echo "<dd class=\"sub p" . $data[3] . "\" ><span><b>" . $data[3] . "</b></span></dd>"; } echo "</dl>"; echo "<ul class=\"xAxis\">"; /* X AXIS */ /* inserts date data into html code for x axis */ for ($d=0; $d < $c; $d++) { echo "<li>" . $date[$d] . "</li>"; } ?> The values are being placed correctly on the chart, but the bars aren't appearing. The CSS code I have for the bars is: /* default column styling */ dl#csschart span{ height:50%; background:url(../images/barx.png) repeat-y; } dl#csschart .sub{ margin-left:-33px; } dl#csschart .sub span{ background:url(../images/subBarx.png) repeat-y; } Just in case it helps, I've print screened how the graph should look. You can see it at: http://allured.info/graph/failgraph.png

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  • VB.net Network Graph code/algorithm

    - by Jens
    For a school project we need to visualise a computer network graph. The number of computers with specific properties are read from an XML file, and then a graph should be created. Ad random computers are added and removed. Is there any open source project or algorithm that could help us visualising this in VB.net? Or would you suggest us to switch to java. Update: We eventually switched java and used the Jung libraries because this was easier for us to understand and implement.

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  • representing graph using database

    - by prosseek
    I need to represent graph information with database. Let's say, a is connected to b, c, and d. a -- b |_ c |_ d I can have a node table for a, b, c, and d, and I can also have a link table (FROM, TO) - (a,b), (a,c), (a,d). For other implementation there might be a way to store the link info as (a,b,c,d), but the number of elements in the table is variable. Q1 : Is there a way to represent variable elements in a table? Q2 : Is there any general way to represent the graph structure using database?

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  • Find a node in a Graph that minimizes the distance between two other nodes

    - by Andrés
    Here is the thing. I have a directed weighted graph G, with V vertices and E edges. Given two nodes in the graph, let's say A, and B, and given the weight of an edge A-B denoted as w(A, B), I need to find a node C so that max(w(A, C), w(B, C)) is minimal among all possibilities. By possibilities I mean all the values C can take. I don't know if it is completely clear, if it's not, I'll try to be more precise. Thanks in advance.

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  • Structure of Astar (A*) graph search data in C#

    - by Shawn Mclean
    How do you structure you graphs/nodes in a graph search class? I'm basically creating a NavMesh and need to generate the nodes from 1 polygon to the other. The edge that joins both polygons will be the node. I'll then run A* on these Nodes to calculate the shortest path. I just need to know how to structure my classes and their properties? I know for sure I wont need to create a fully blown undirected graph with nodes and edges.

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  • Questioning the motivation for dependency injection: Why is creating an object graph hard?

    - by oberlies
    Dependency injection frameworks like Google Guice give the following motivation for their usage (source): To construct an object, you first build its dependencies. But to build each dependency, you need its dependencies, and so on. So when you build an object, you really need to build an object graph. Building object graphs by hand is labour intensive (...) and makes testing difficult. But I don't buy this argument: Even without dependency injection, I can write classes which are both easy to instantiate and convenient to test. E.g. the example from the Guice motivation page could be rewritten in the following way: class BillingService { private final CreditCardProcessor processor; private final TransactionLog transactionLog; // constructor for tests, taking all collaborators as parameters BillingService(CreditCardProcessor processor, TransactionLog transactionLog) { this.processor = processor; this.transactionLog = transactionLog; } // constructor for production, calling the (productive) constructors of the collaborators public BillingService() { this(new PaypalCreditCardProcessor(), new DatabaseTransactionLog()); } public Receipt chargeOrder(PizzaOrder order, CreditCard creditCard) { ... } } So dependency injection may really be an advantage in advanced use cases, but I don't need it for easy construction and testability, do I?

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  • Dynamically changing DVT Graph at Runtime

    - by mona.rakibe(at)oracle.com
    I recently came across this requirement where the customer wanted to change the graph type at run-time based on some selection. After some internal discussions we realized this can be best achieved by using af:switcher to toggle between multiple graphs. In this blog I will be sharing the sample that I build to demonstrate this.[Note] : In the below sample, every-time user changes graph type there is a server trip, so please use this approach with performance implications in mind.This sample can be downloaded  from DynamicGraph.zipSet-up: Create a BAM data control using employees DO (sample)(Refer this entry)Steps:Create the View Create a new JSF page .From component palette drag and drop "Select One Radio" into this page Enter some Label and click "Finish"In Property Editor set the "AutoSubmit" property to trueNow drag and drop "Switcher" from components into this page.In the Structure pane select the af:switcher right click and surround with "PanelGroupLayout"In Property Editor set the "PartialTriggers"  property of PanelGroupLayout to the id of af:selectOneRadioAgain in the Structure pane select the af:switcher right click and select "Insert inside af:switcher->facet"Enter Facet name (ex: pie)Again in the Structure pane select the af:switcher right click and select "Insert inside af:switcher->facet" Enter  another Facet name (ex: bar)From "Data Controls" drag and drop "Employees->Query"  into the pie facet as "Graph->Pie" (Pie: Sales_Number and Slices: Salesperson)From "Data Controls" drag and drop "Employees->Query"  into the bar facet as "Graph->Bar" (Bars :Sales_Number and X-axis : Salesperson).Now wire the switcher to the af:selectOneRadio using their "facetName" and "value" property respectively.Now run the page, notice that graph renders as per the selection by user.

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