The Whiteboard

4:00 PM

They have interfaces between them. The interface may not be method calls, but formats for Protocol Buffers, XML messages, custom binary formats, CORBA method calls, RMI invocations, whatever.

UML is not limited to object-oriented software. Some of the diagrams are more suited to object-oriented software, but I can use a class diagram to represent a C program.

overexchange

I did not understand from coding perspective, what interfaces mean here in component diagrams?

Thomas Owens

It just means that you specify how to get data or messages into and out of the component.

For example, your interface could be that LanguageTranslator is part of a pub/sub system on a JMS-compliant message queue.

And it reads and publishes binary messages that conform to some ProtoBuf IDL format.

overexchange

this is not java interface ?

Thomas Owens

It can be. But it doesn't have to be.

It's an interface in the more abstract sense.

Your input could even by a physical input - a sensor, a dial, a keyboard.

Interface (computing)

In computing, an interface is a shared boundary across which two separate components of a computer system exchange information. The exchange can be between software, computer hardware, peripheral devices, humans and combinations of these. Some computer hardware devices such as a touchscreen can send and receive data through the interface, while others such as a mouse, microphone or joystick are one way only. == Hardware interfaces == Hardware interfaces exist in many of the components such as the various buses, storage devices, other I/O devices, etc. A hardware interface is described by...

It's any shared boundary.

overexchange

ok

wrt my point about component diagram of holiday-reservation system, I see that you can come with those components only after you design classes and logically group those classes in a component(i feel this is java package)

Thomas Owens

4:08 PM

@overexchange Not necessarily.

overexchange

so I see this leads from model driven engineering

Thomas Owens

For example, in a complex system, you typically start with functional decomposition.

So you group related functions into components. And some components may not even be software components.

overexchange

functional decomposition you mean feature decomposition

Thomas Owens

No. See functional decomposition in Systems Engineering.

overexchange

yes, before we model, we come up with components and then for each component, we decide what models are required

whatsisname

4:10 PM

I get the vibe that @ThomasOwens works on ultra-configurable enterprise monstrosity type software

Thomas Owens

Yes. However, you may want to graphically represent what the components are. That can be a graphical model.

@whatsisname Nope.

I make this.

overexchange

so when a use case description is provided from data analyst, designers first decide the components and relation between components and then each component will have their own models(java classes)

Robert Harvey

It's a good thing that there isn't actually a set order of steps that you perform to engineer software, because if there were, I'd be fucked.

Thomas Owens

@overexchange Usually. And what the model is can vary. It is important to choose the right model. It could be an ER diagram, UML models, even pseudocode for algorithms or prototype implementations can be models.

Robert Harvey

Software design is still more art than science.

Thomas Owens

4:13 PM

@RobertHarvey I'm even advocating to less templates at work. That's not going well, sadly, since corporate likes everything standardized.

overexchange

you mean ER diagram for a DB system component

Thomas Owens

I've been trying for two weeks to build a single outline for a design description, limiting myself to the software that we build in one building for one type of application. Not possible.

Robert Harvey

That's why corporations like Java. Oh, the boilerplate.

Thomas Owens

@overexchange Yeah, if you have a database or some kind of data storage, you can model it with ER. It's all about choosing the right language for communicating with your audience.

There's no one-size-fits-all approach to anything.

overexchange

@ThomasOwens Do you know any such case study on internet that can take me from use case -> components -> modeling -> ..?

Thomas Owens

4:16 PM

@overexchange I do not.

user55340

> Show me your flowcharts and conceal your tables, and I shall continue to be mystified. Show me your tables, and I won't usually need your flowcharts; they'll be obvious.

2

Robert Harvey

@overexchange Hopefully you're flexible enough to relearn everything when it all changes in 5 years.

Thomas Owens

@MichaelT It gets more difficult when dealing with third-parties. You may not want to show them your tables.

user55340

(Fred Brooks)

Thomas Owens

Where tables is any internal details.

whatsisname

4:18 PM

@RobertHarvey: if there was a set order of steps, we would have written software to do it

user55340

@ThomasOwens they're also unlikely to give you UML too.

whatsisname

and then we'd have some sort of new economy based around whatever comes after that

overexchange

Within a component, ER diagrams or java classes can be considered models, but why would you consider pseudocode for algorithms or prototype implementations as models?

Thomas Owens

@MichaelT Probably detailed UML, sure. Some models may be appropriate. State diagrams, for example, may be useful to external entities to visualize how your system behaves as they work with it.

Jimmy Hoffa

@ThomasOwens hey, you keep your tables to yourself little mister! Yeesh, coders these days...

Thomas Owens

4:20 PM

@overexchange Pseudocode almost always. What is a model, anyway? Just a tool to help understand or document.

Robert Harvey

@ThomasOwens Just replace "tables" with "sensibly-designed API's and well-written documentation," and the statement still applies.

user55340

... Any useful UML. Which presupposes that there can be such a thing. ;-)

Robert Harvey

I can't remember the last time I made a UML diagram or flow chart. The closest thing I've come to that is class diagrams.

Though there was the occasional data flow diagram.

overexchange

@ThomasOwens the product I worked for uses bdb database, so our product statically links all BDB c code to our product. I reverse engineered and found the schema of the database that has 7 tables.

Robert Harvey

@MichaelT There used to be a tool that could draw a flowchart from pseudocode, a very nice flowchart with rounded corners and good layout. Alas, it was not open-source, and I don't think it exists anymore.

overexchange

4:24 PM

@ThomasOwens When components work tightly with servlet frameworks of tomcat(third party say), how do we design the components of server side?

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