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  • Inheritance vs specific types in Financial Modelling for cashflows

    - by BlueTrin
    Hello, I have to program some financial applications where I have to represent a schedule of flows. The flows can be of 3 types: - fee flow (just a lump payment at some date) - floating rate flow (the flow is dependant of an interest rate to be determined at a later date) - fixed rate flow (the flow is dependant of an interest rate determined when the deal is done) I need to keep the whole information and I need to represent a schedule of these flows. Originally I wanted to use inheritance and create three classes FeeFlow, FloatingFlow, FixedFlow all inheriting from ICashFlow and implement some method GetFlowType() returning an enum then I could dynamic_cast the object to the correct type. That would allow me to have only one vector to represent my schedule. What do you think of this design, should I rather use three vectors vector, vector and vector to avoid the dynamic casts ?

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  • Data Warehouse: Modelling a future schedule

    - by Pat
    I'm creating a DW that will contain data on financial securities such as bonds and loans. These securities are associated with payment schedules. For example, a bond could pay quarterly, while a mortage would usually pay monthly (sometimes biweekly). The payment schedule is created when the security is traded and, in the majority of cases, will remain unchanged. However, the design would need to accomodate those cases where it does change. I'm currently attempting to model this data and I'm having difficulty coming up with a workable design. One of the most commonly queried fields is "next payment date". Users often want to know when a security will pay next. Therefore, I want to make it as easy as possible for them to get the next payment date and amount for each security. Also, users often run historical queries in which case they'd want the next payment date and amount as of a specific point in time. For example, they may want to look back at 1/31/09 and query the next payment dates (which would usually be in February 2009 for mortgages). It's also common that they want to query a security's entire payment schedule, which might consist of 360 records (30 year mortgage x 12 payments/year). Since the next payment date and amount would be changing each month or even biweekly, these fields wouldn't seem to fit into a slow-changing dimension very well. It would probably make more sense to use a fact table, but I'm unsure of how to model it. Any ideas would be greatly appreciated.

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  • Would like some modelling tips for dependent values

    - by orjan
    I'm working on a model for a simple fishing competition and I have some issues with my design. The main class for the fishing game is Capture and it looks like this: public class Capture : Entity { public virtual int Weight { get; set; } public virtual int Length { get; set; } public virtual DateTime DateForCapture { get; set; } public virtual User CapturedBy { get; set; } public virtual Species Species { get; set; } } So far there´s no problem but I'm not really sure how to model the game. Every Species is connected to a reference weight that changes from year to year The number of point for a capture is its Weight divided by the current reference weight for the species. One way to solve the problem is to connect a capture to SpeciesReferenceWeight instead of Species public class SpeciesReferenceWeight : Entity { public virtual Species Species { get; set; } public virtual int ReferenceWeight { get; set; } public virtual int Year { get; set; } } But in that way that Capture is connected to the implementation details of the game and from my point of view a capture is still a capture even if it's not included in a game. The result I'm aiming for is like: http://hornalen.net/fishbonkern/2007/ that I wrote a couple of years ago with brute force sql and no domain model. I would be very happy for all kinds of feeback on this issue.

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  • How to show or direct a business analyst to a data modelling subject?

    - by AaronLS
    Our business analysts pushed hard to collect data through a spreadsheet. I am the programmer responsible for importing that data. Usually when they push hard for something like this, I never know how well it will work out until a few weeks later when I have time assigned to work on the task of programming the import of the data. I have tried to do as much as possible along the way, named ranges, data validations, etc. But I usually don't have time to take a detailed look at all the data and compare to the destination in the database to determine how well it matches up. A lot of times there will be maybe a little table of items that somehow I have to relate to something else in the database, but there are not natural or business keys present that would allow me to do so. Make the best of this, trying to write something that can compare strings and make a best guess at it and then go through the effort of creating interfaces for a user to match the imported data to the destination. I feel like if the business analyst was actually creating a data model, they would be forced to think about these relationships, and have an appreciation for the need of natural or business keys to be part of the spreadsheet for the purposes of smoothly importing the data. The closest they come to business analysis is a big flat list of fields, and that would be fine if it were like any other data dictionary and include data types+relationships, but it isn't. They are just a bunch of names. No indication of what type of data they might hold, and it is up to me to guess. When I have pushed for more detail, they say that it is just busy work. How can I explain the importance of data modelling? How can I tell them what it is and how to do it? It feels impossible, because they don't have an appreciation for its importance. They do however, usually have an interest in helping out in whatever way they can, it's just this in particular has never gotten a motivated response.

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  • How to show or direct a business analyst to do data modelling?

    - by AaronLS
    Our business analysts pushed hard to collect data through a spreadsheet. I am the programmer responsible for importing that data. Usually when they push hard for something like this, I never know how well it will work out until a few weeks later when I have time assigned to work on the task of programming the import of the data. I have tried to do as much as possible along the way, named ranges, data validations, etc. But I usually don't have time to take a detailed look at all the data and compare to the destination in the database to determine how well it matches up. A lot of times there will be maybe a little table of items that somehow I have to relate to something else in the database, but there are not natural or business keys present that would allow me to do so. Make the best of this, trying to write something that can compare strings and make a best guess at it and then go through the effort of creating interfaces for a user to match the imported data to the destination. I feel like if the business analyst was actually creating a data model, they would be forced to think about these relationships, and have an appreciation for the need of natural or business keys to be part of the spreadsheet for the purposes of smoothly importing the data. The closest they come to business analysis is a big flat list of fields, and that would be fine if it were like any other data dictionary and include data types+relationships, but it isn't. They are just a bunch of names. No indication of what type of data they might hold, and it is up to me to guess. When I have pushed for more detail, they say that it is just busy work. How can I explain the importance of data modelling? How can I tell them what it is and how to do it? It feels impossible, because they don't have an appreciation for its importance. They do however, usually have an interest in helping out in whatever way they can, it's just this in particular has never gotten a motivated response.

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  • Entity Relationship Diagramming

    - by Ben Aston
    I'd like to improve my understanding of cardinality constraints in ER diagrams. I have two entities: User Location But, I want the relationship between these two entities to be many-to-many (a user can be in many locations and a location can have many users). To do this I need to introduce an association class UserLocation. Is it correct to say I now have 3 entities? If I were to draw an ER diagam of the above, would I draw in the UserLocation entity, and would the cardinality look like this? User 1 ------ * User Location * ------ 1 Location

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  • Model Based Testing Strategies

    - by Doubt
    What strategies have you used with Model Based Testing? Do you use it exclusively for integration testing, or branch it out to other areas (unit/functional/system/spec verification)? Do you build focused "sealed" models or do you evolve complex onibus models over time? When in the product cycle do you invest in creating MBTs? What sort of base test libraries do you exclusively create for MBTs? What difference do you make in your functional base test libraries to better support MBTs?

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  • 3D Character/Model Creator

    - by Click Ok
    I'm in a project to create a 3d game using XNA/C#, and the game will use a lot of 3d characters. Looking at the current 3d games, in some they create near to hundreds of characters, what lead me to think that there are some good 3d character/model creator. To narrow the sample, the game will have characters like the game "Grand Chase". There are some good (and easy) character model creator for to use in XNA development? Free is better, of course, but I will get payed versions too. EDIT: Another question is about the movements of the characters. The movements like walk, jump, sit, etc are "created" by the "character creator tool" or by the game?

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  • Implementing Domain Driven Design

    - by Steve Dunn
    Is anyone using the techniques from Domain Driven Design? I've recently read the Eric Evans book of the same name (well, most of it!) and would be interested to hear from anyone who's implemented all/some of it in a project (particularly in C#/C++) I've kept this question open ended as I'd like to see as many comments as possible, but I have a few questions in particular: 1 - Should value types be real 'value types' if the language supports it? e.g. a struct in C# 2- Is there any feature in C# that makes clearer the association between the language and the model (for instance, this is an entity, this is an aggregate etc.)

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  • How to convert EER to SQL Table?

    - by Khajavi
    I have no problem with converting ER to SQL tables, but I don't know how can I convert EER to SQL tables? as you Know that EER has "is a" specification and inheritance, but I don't know how relational databases can connect with inheritance specification

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  • strategies for learning complex software packages

    - by Tom
    I am a fairly novice Java programmer and I am currently working on a project to extend a piece of software that has been developed over a few years. So it has pretty big code base and the previous developers knew it well, so extending it is not going to be easy without a thorough understanding of the structure and function. 1) I had begun by trying to tackle small parts of the system and document them with mindmap. (particularly I am trying to document the interactions with external systems) 2) I have the book "code complete", which I am working through. 3) I have pointed some tools like "tattletale" at the code to get some diagrams of dependency relationships. What other strategies should I employ, should I focus on one particular aspect?

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  • Should I use Enumeration or Class stereotype in UML to represent a type directory table?

    - by Ivan
    Let's take 2 UML class model entities: One represents an actual Order and another represents an Orede Type. Any Order corresponds to one Type. A 2-way-naviglabe many Orders to one Type relation is meant. Order Type instances are, for example, "Request availability", "Request price", "Preorder", "Buy", "Cancel", "Request support", etc. Order Types are to be addable and editable in the resulting application. Should I model Order Type as Class or as Enumeration? From the data perspective I can't see the difference actually.

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  • Example where Up-Front Design (Would have) Saved You Time

    - by Winston Ewert
    In various places I've seen the claim that by designing a system up-front, you can significantly reduce development time. I.e. by spending an hour designing you can save a week coding. My problem is that I have never seen a situation where I found this to be true. So I want to know of any examples out there that people have where this would be true: So: What sort of problem arose during coding? (or was avoided?) How could you have avoided (or did avoid) the problem by spending more time doing design? Why was it (or would it have been) hard to fix the problem in the code?

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  • What initial modelling/design activities on Agile Projects do you do??

    - by dalton
    When developing an application using agile techniques, what if any initial modelling/architecture activities do you do, and how do you capture that knowledge?? I'm not after a bullet list about XP, Scrum, Crystal, DSDM..etc as I'm familiar with the methodologies. But what do you do above and beyond the guidance given by these. I find I work best by thinking the system through first, but also like the benefits of timeboxing, story cards, pairing, tdd. The closest thing I've seen so far is Scott Ambler's Initial Architecture Modelling, but was wondering what alternatives are used out there?

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  • When should we use weak entities when modelling a database?

    - by Songo
    This is basically a question about what are weak entities? When should we use them? How should they be modeled? What is the main difference between normal entities and weak entities? Does weak entities correspond to value objects when doing Domain Driven Design? To help keep the question on topic here is an example taken from Wikipedia that people can use to answer these question: In this example OrderItem was modeled as a weak entity, but I can't understand why it can't be modeled as a normal entity. Another question is what if I want to track the order history (i.e. the changes in it status) would that be a normal or weak entity?

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  • What modelling technique do you use for your continuous design?

    - by d3prok
    Together with my teammates, I'm trying to self-learn XP and apply its principles. We're successfully working in TDD and happily refactoring our code and design. However we're having problems with the overall view of the design of the project. Lately we were wondering what would be the "good" practices for an effective continuous design of the code. We're not strictly seeking the right model, like CRC cards, communication diagrams, etc., instead we're looking for a technique to constantly collaborate on the high level view of the system (not too high though). I'll try to explain myself better: I'm actually interested in the way CRC cards are used to brainstorm a model and I would mix them with some very rough UML diagrams (that we already use). However, what we're looking for are some principles for deciding when, how and how much to model during our iterations. Have you any suggestion on this matter? For example, when your teammates and you know you need a design session and how your meetings work?

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  • Information I need to know as a Java Developer [on hold]

    - by Woy
    I'm a java developer. I'm trying to get more knowledge to become a better programmer. I've listed a number of technologies to learn. Instead of what I've listed, what technologies would you suggest to learn as well for a Junior Java Developer? I realize, there's a lot of things to study. Java: - how a garbage collector works - resource management - network programming - TCP/IP HTTP - transactions, - consistency: interfaces, classes collections, hash codes, algorithms, comp. complexity concurrent programming: synchronizing, semafores steam management metability: thread-safety byte code manipulations, reflections, Aspect-Oriented Programming as base to understand frameworks such as Spring etc. Web stack: servlets, filters, socket programming Libraries: JDK, GWT, Apache Commons, Joda-Time, Dependency Injections: Spring, Nano Tools: IDE: very good knowledge - debugger - profiler - web analyzers: Wireshark, firebugs - unit testing SQL/Databases: Basics SELECTing columns from a table Aggregates Part 1: COUNT, SUM, MAX/MIN Aggregates Part 2: DISTINCT, GROUP BY, HAVING + Intermediate JOINs, ANSI-89 and ANSI-92 syntax + UNION vs UNION ALL x NULL handling: COALESCE & Native NULL handling Subqueries: IN, EXISTS, and inline views Subqueries: Correlated ITH syntax: Subquery Factoring/CTE Views Advanced Topics Functions, Stored Procedures, Packages Pivoting data: CASE & PIVOT syntax Hierarchical Queries Cursors: Implicit and Explicit Triggers Dynamic SQL Materialized Views Query Optimization: Indexes Query Optimization: Explain Plans Query Optimization: Profiling Data Modelling: Normal Forms, 1 through 3 Data Modelling: Primary & Foreign Keys Data Modelling: Table Constraints Data Modelling: Link/Corrollary Tables Full Text Searching XML Isolation Levels Entity Relationship Diagrams (ERDs), Logical and Physical Transactions: COMMIT, ROLLBACK, Error Handling

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  • Name that blog entry - Modelling changes over time with two db columns only.

    - by disown
    I vaguely remember reading a blog entry (written by a well-known blogger I think) about how to model price changes over time, and that you could model most changes by saving two dates only (two columns in a db). The blog talked about prices on a website changing over time and how you could figure out the right price to charge knowing only when the purchase had been made. Very vague, I know, but my google-fu is failing me, everyone at IRC are busy talking about other stuff and I don't know what to do! :)

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  • How to speed-up Eclipse startup?

    - by Ivan
    I've installed Eclipse Modelling Framework (eclipse-modeling-galileo-SR1-incubation-linux-gtk.tar.gz) by extracting 'features' and 'plugins' filders of the package to '~/.eclipse/org.eclipse.platform_3.5.0_1543616141'. And now Eclipse splashscreen is shown for many minutes (the whole system (incl. BIOS, Linux and KDE) takes much less time to start). I don't need Eclipse Modelling Framework to be loaded at startup, if it is, I only need it when I start a modelling project. How to set up Eclipse to start faster and don't load all the plugins at startup time? My system runs Arch Linux 2010.05, OpenJDK 6.0, Eclipse 3.5.2.

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