Property nodes are "upside down" - discuss!

[Justin Goeres]

QUOTE (bsvingen @ Feb 25 2009, 04:17 PM)

Yes, but I don't see how the ability to make the wires invisible (transparent) will prevent you from doing that. I mean, this would basically be an implementation of layers, that have existed in CAD/graphical programs for decades.

Dataflow code (i.e. what you write in LabVIEW) is fundamentally the expression of relationships between pieces of data. That's one of the key differences between dataflow and imperative programming. And those relationships (in this case, the wires) determine the execution order of elements of your block diagram. If the error wires, or any other wires for that matter, were hidden, you would be hiding key information about your program's execution from yourself (not to mention anyone else unfortunate enough to see it!). Just for starters, you'd be unable to tell if a particular new wire you create would form a cycle (circular data dependency). And if it did, you'd be equally unable to tell why your diagram was suddenly broken.

At runtime, the error wire also contains critical information about the outcome of whatever operations preceded it. That information is used to make all kinds of decisions, as other people pointed out. In the process of making these decisions, the error wire can branch and merge in complicated ways that affect the execution flow of the program. Masking out that kind of information would break the entire relationship between looking at your block diagram and understanding how its code executes.

Hiding the error wires would break the whole dataflow paradigm. It would be like hiding all the individual "if" statements in C code, but not the code inside the { } blocks that follow them, or something.

I would suggest that if you really are having trouble with error wires polluting your block diagrams, you've got too much going on in your diagrams and should use more subVIs.

[robijn]

QUOTE (Ic3Knight @ Feb 25 2009, 03:32 PM)

I was just doing some coding and getting information out of a property node, and it struck me that, from a style point of view at least, property Wouldn't it make sense for the base part of the propery node (i.e. the class label) to be at the bottom with the error, and then you could open the properties terminals upwards...

The crossings of wires at property nodes have annoyed me as well.

Could it be an option of the node to have the error connectors of property/invoke nodes be placed the the bottom ? Then it would be in line with the commonly accepted style, without too much changes. Refs at top, data in the middle, error at bottom.

Joris

[Yair]

I think I like the idea of moving the error wire to the top. I did a quick mockup (no screenshot, sorry) and I think it actually looks good. Stephen, I would suggest that R&D play with it for a bit to see how it works. If it looks good NI could probably create a reasonably simple UI for automatically modifying the wiring of existing VIs based on a user request. Of course, I would probably like more the idea of better error handling, but that's another discussion.