Vladislav Bronin presents a process for a team of designers to use in AutoCAD (and its verticals) when working together on the same project.
"Indication of building services on a ceiling layout always requires lots of communication and coordination between electrical, HVAC, heating, and sprinkler designers to make it clear and with no discrepancies. When you place your discipline's fixture/unit, it's hard to know whether the ceiling spot you have occupied is not taken already by someone else. Here the external reference (xref) with 'Attach' and 'Overlay' comes to help.
"Each of the designers will have to do the following: First, attach the background (floor and ceiling layouts) to each discipline's drawing. The simplest way: make it only once to the drawing that will be the base for the others (typically, it's the lighting layout). Both floor and ceiling layouts should be 'Attached' to the base drawing, to make them visible in all other drawings the base one will be nested in.
"Once the base drawing is settled, the game begins. Every designer should attach the drawings of others into his/her working space. And here the trick: these attachments should be done by 'Overlaying.' By doing so you will not only avoid circular references, but also avoid confusion for yourself and others. It doesn't matter how many other drawings were 'Overlayed' into yours; when someone else will 'Overlay' it to his/her working space, the only thing he/she sees are the elements of your drawing and nobody else's.
"Finally, once all the other drawings are in, you can see what other designers have done so far, and where their services are shown. All unnecessary layers of these xrefs could be frozen and those relevant to your work (e.g., diffusers, sprinkler heads, lights, radiant panels, etc.) could be changed to lighter colors. This, of course, will be possible if the main rule is followed by every designer in the team — the objects are to be drawn 'ByLayer' and on the proper layer."
Notes from Cadalyst tip reviewer Brian Benton: Working with others on the same project can be tricky. The key is to make sure everyone has correct, up-to-date information. This workflow makes sense and can easily be tweaked to fit specific circumstances. Just keep in mind that an "attached" xref will always go with the file it is attached to. An xref that is an "overlay" will only show up when that file is opened. The data doesn’t follow.