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I'm looking at a new project where the customer wants to use RS232 serial comms to exchange information between 2 embedded systems.
(They need the new system to support legacy boxes, they can change the protocol on the old boxes but will not chnage the hardware. At the momment each box has is own way.)
I'm having trouble locating an industry standard for the protocol. I've found ISO 1745 which looks like it should do the job but its dated 1975 and that just feels wrong.
Does anyone know of a more recent industry standard that defines point to point data exchange over RS232?
Thanks
Alec
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AlecJames wrote: Does anyone know of a more recent industry standard that defines point to point data exchange over RS232?
It seems to be discussed here[^] and there are reference links at the bottom that may link to the specs.
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Hi,
you can use any protocol you like, or come up with your own; I often have.
It all depends on your needs (throughput, reliability, recovery, multi-drop, etc).
One not so simple example is SLIP.
If you roll your own, first decision is binary versus text (compactness versus ease of communication, getting all characters through the driver/modem/...).
Whatever you choose, make sure you know to locate the end of each message: either prefix the length, or set a unique terminator (CR and/or LF on text).
Luc Pattyn [Forum Guidelines] [My Articles]
The quality and detail of your question reflects on the effectiveness of the help you are likely to get.
Show formatted code inside PRE tags, and give clear symptoms when describing a problem.
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Hi Experts , getting into the details directly , I'm doing a 3 tier application and I have some questions before I start coding.
1. we have 2 servers one for the database and the other for networking and domain control, since this is a 3 tier application I assumed I have to lay one of the layers on the DC server, BLL layer for example and I'm still confused about the DAL layer if better to locate it on the DC server or on the DB server ?
2. What about ConnectionStrings and References - VisualStudio C# 2008 - , as I'm working on my development laptop , I want to work even when I'm not at work . If I simulate the environment locally can I move it to the real world gently ? and how can I do so ?
Thanks in Advance
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1. The tiers are a conceptual separation, not a separation over servers. May I suggest that you keep both the DAL and the BL on the DB-server? That would save you from writing (secure) communication-code between those layers.
2. Yes. By putting the connectionstring in a configuration file.
I are troll
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I have a scenario where I have three combos. All three are populated with the same data, but use different fields from the data for their display text. The Extension, Name, and Room combos are all populated from the Extension table. If the user selects an extension, the Room and Name combo selections must update to the values for the selected extension. The same if they select a Name, then extension and room get updated.
Often, many extensions are found in one room, or under one name, etc. So now, if the user selects a 'busy' room, what I figure I'll do is filter the extension combo to only those for that room, and give a visual indication of this, maybe a visible link between the combos. If the user decides they wish to ignore the room, and search all extensions, they click a 'clear' entry in extensions, and it loads all the extensions.
Is this a feasible way of doing this? Are there any established patterns for scenarios like this?
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We do something similar except we use check boxes to determine whether or not to link the combos. The check boxes provide the visual feedback so that the user knows whether or not they're seeing filtered data and at the same time allows them to control whether or not they want to see filtered data.
I don't know of any established patterns for this but it really doesn't take that much to implement a solution.
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Hi,
I'm modeling a tagging system, like my own html, for an application... and this is what I have till now:
class Tag:
+Tag(string) //example new Tag("<i>...</i> ... <s>...</s>")
+string Name //for example "b" (for a tag which is used like <b>..</b>)
+string Content //example "<i>...</i> ... <s>...</s>"
+Tag[] Tags //the subtags used within the content of the tag, in the example above it would return the tags t1 and t2 (i and s)
But i need more ideas before getting into the code so I dont get a headache within the process
Thanks.
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Also somehow I need to have a list of possible tags, for the parsing -private- method..
Maybe another class, TagAnalyzer?
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If one or more private methods of a class need a variable to perform some operation on, should one methods pass it to the other as parameters or should we make the parameter a private member of the class so both methods can access it?
If we make it a class level variable then it will exist for the lifetime of the object. If we do not need it for the lifetime of the object, we are wasting resources.
If we do not make it a class level variable then we have to pass it around to methods which need it. I am not sure what the disadvantage is here.
If the class has 7 methods and 5 of them need the variable then we will pass it around to all these methods. If class level, then we will not need to pass it but it will exist for the lifetime of the object.
Should it depend on how many different methods need the variable or should it depend on whether we need its existence for the lifetime of the object?
What are your opinions? Any conventions?
CodingYoshi
Visual Basic is for basic people, C# is for sharp people. Farid Tarin '07
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Hi,
it depends on the circumstances.
If the parameters are like characteristics of the objects, then data members would be alright.
If they are small, then having storage allocated for them for the lifetime of the object probably is irrelevant.
If they more act like operational parameters, seems to me method parameters are in order; if they are many, you may want to create a separate struct or class to hold them and pass them around easily (kind of "job ticket").
Luc Pattyn [Forum Guidelines] [My Articles]
The quality and detail of your question reflects on the effectiveness of the help you are likely to get.
Show formatted code inside PRE tags, and give clear symptoms when describing a problem.
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I'm lookin for a design-pattern that match what I need: I have class A which should hold a collection of class B or its inehrited classes. class B should be able to run functions and access properties on A and A should be able to run functions and access properties on B.
I've been suggested to pass reference of As properties to B opon construction, but I'm lookin for the design-pattern...
anyone know of any design-pattern similar to this?
Thanks alot
NaNg.
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That is the pattern, pass A to B in its constructor. Or make B an inner class of A so only A can create it and without A its creation will be impossible. Here is a snippet:
A a = new A();
B b = a.CreateB();
public class A
{
...
public void CreateB()
{
A a = new A(this);
return a;
}
...
public class B // Or other access depending on your needs
{
B(A a)
{
this.a = a;
}
}
}
CodingYoshi
Visual Basic is for basic people, C# is for sharp people. Farid Tarin '07
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the thing is - i was strongly advised not to hold the A class instance in Bs instance, someone told me it's bad design.
What do you think? is it that bad of a design, could there be better? or this is the best option there is?
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I don't think it is a bad design. Like I said in assemblies this will cause problems as Assembly A will depend on B to compile and B will depend on A to compile. This is a deadlock situation. With classes, I don't see the problem. You should try to minimize coupling but you can not avoid it altogether.
.NET and Java API both have instances of classes within other classes. For example, DataSet.Tables, Table.Rows etc.
People waste way too much time on design and design patterns. Patterns are suppose to make the construction easier and not introduce complications. The best design is the simplest design.
CodingYoshi
Visual Basic is for basic people, C# is for sharp people. Farid Tarin '07
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I would say you are looking for the Composite pattern: http://en.wikipedia.org/wiki/Composite_pattern[^].
With this pattern the quick solution is to make class A the composite and class B an component.
A more beautiful solution is to create an abstract Component class that just contains the functionality related to administering the tree data structure. You then create 2 implementations of this abstract class:
- class B that just re-uses the methods of the abstract class and adds its own functionality,
- class A that just re-uses the methods of the abstract class, but adds collection functionality and its own functionality.
A very beautiful solution is to separate specification from implementation:
- specify B's own functionality in an interface IB,
- specify A's own functionality in an interface IA,
- make an abstract class Component that contains child logic,
- make an abstract class Composite that contains collection logic,
- make a class B that inherits class Component and implements IB,
- make a class A that inherits class Composite and implements IA.
In the implementation of class B, you can now check, if the parent is of type IA, and then use the functionality of IA.
In the implementation of class A, you can now check, if a child is of type IB, and then use the functionality of IB.
You can even make interfaces for the Component and the Composite, if you go 100%.
Hope above was a little helpful. Remember, you decide your design!
Regards, Keld Ølykke
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Hello to all readers,
I'm reading now for a while requirements-literature and the more I read, the more I'm confused.
One of my basic questions is: What is in a SRS?
a)
are there user-requirements exclusively?
(e.g. "data must be stored" )
b)
or are there only requirements for my software which are derived from the user-requirements?
(e.g. data are stored in a SQL-Database)
c)
Is any architecture/design specification/model also included in a SRS?
Does somebody have a nice link?
Best regards
modified on Sunday, May 24, 2009 1:02 PM
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User Requirement and SRS (System Requirements Specification) is not the same.
There is a fundamental difference.
User Requirement is recorded in a User Requirement Specification.
Whereas in SRS, we record the system behavior and functionality. SRS focuses on the system purely and is derived from the URS (User Requirement Specification). However in SRS, we can also put any non-functional requirement like Performance requirement, Environment Requirements and so on so forth.
In SRS, we can put in User Case Diagrams, but not pure system diagrams which should be put in High Level Design Specs, Module Specs or Low Level Design specs.
Hope this clear your doubts. Any queries, please feel free to contact me.
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Thank you for your reply. I'm currently fighting hard with the terms. I read a lot more meanwhile (e.g. Axel van Lamsweerde: Requirements Engineering) and I hope this cleaned up my mind.
Let me tell my ideas in the following (should be compliant to your statements). Can you revise my statements?
1)
A user requirement is what I get from any customer - exclusively in his words (problem-domain) (e.g. "the route of the truck must be planned in advance"). This is content of a "user requirement specification" (URS).
2)
From this URS I derive a SRS (e.g. by Object Oriented Analysis).
An SRS does not contain any solution elements (e.g. Architecture, Design,..); It deals only and exclusively with the problem-domain. The goal is to structure the problem domain.
There are three basic elements for getting some abstraction/organization into the problem-domain:
a) Object-Diagrams for the structure (e.g. based on UML class diagrams)
b) Behavioral Diagrams (e.g. state-machines)
c) Operational Diagrams (e.g. Usecases,Szenarios,...)
d) Beside of this there is usually a "textual" description of the "nonfunctional" Requirements.
Alternatively parts a), b) and c) can exclusively also be expressed in "natural language"
All this is SRS
3)
After that the first technical elements come into the play. e.g. Architecture followed by design,...
Do you agree to this sequence and content?
Thank you again for your reply
Best regards
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Great!!! You are absolutely correct.
Now you have very good clarity on the User Requirement, Functional Requirement Specs.
Regarding the Architecture and Technical Designs, based on the complexity of the system, you can have elaborated Use-Case designs in the Form of High Level Design Specs.
In the next level, you can have Low Level Design Specs or Unit Secification detailing the objects, entities etc for the relevant Unit of the System in great detail. Unit Specs often acts as the blue print for the developer of the system and you should be able to derive Unit Test Cases from the Unit Specs.
System Test Cases from the SRS.
Integration Test Cases from High Level Design Specs and Unit Specs.
Hope this helps you.
Feel free to contact me, if you have any doubts / queries.
Regards,
Robin
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Hi Roy,
for the moment I'm fine.
Thank you for your support - it helped me a lot
Best regards
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Hey Frygreen,
No problems.
Thanks,
Robin
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Hello to all, it's me again.
Reading more and more, I begin to doubt my own statements in my last contribution.
Here I wrote under point b): " ... no arichitectural elements .... It (SRS) deals only and exclusively with the problem-domain. The goal is to structure the problem".
Is this really true?
Does a SRS really have no SW-architectural Elements? Is it's only purpose to structure/understand the problem-domain?
If this is true, then: Where are the models for architecture coming up?
Best regards
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Lets say I have 3 classes: Category, Book, and BookCollection. Objects of Category class will have a BookCollection which is simply some container which contains all the books within that category. These classes also have a method Save() which saves them to a permanent storage. Now when Category's Save() method is called, should it just save the category or the books within the category as well? What are the advantages and disadvantages?
If Category.Save() only saves itself, then clients will also need to call Category.Books.Save(). What is better? Also, should BookCollection.Save() traverse the books and call Save on each or will it do all the saving?
I guess it depends on the context but is there a convention?
CodingYoshi
Visual Basic is for basic people, C# is for sharp people. Farid Tarin '07
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