I am not quite certain what you are trying to do here.
Here are some assumptions. Post back with corrections where I am wrong.
1. You are using a style-based AEC object to model/represent the light fixtures, such as a Multi-View Blocks or Mask Blocks.
2. You have a separate style/definition for each different fixture. (Or are you using one style/definition with "representational" graphics to cover multiple fixtures and/or multiple fixture options?)
If you have a separate style/definition for each unique combination of fixture options, you could make a style-based Property Set Definition and set up properties for each fixture attribute you want to show in the schedule. You could set up a List Definition for each property to assure uniformity in the property values, but since the values would be entered once for each definition and require no subsequent user editing (unless things change, of course), that may be overkill.
The downside of the previous scenario is needing a separate style/definition for each unique fixture type. If you are not modeling in sufficient detail to show differences in trim or rough-in frame or any variations between manufacturers, you may prefer to have just three styles/definitions, one for each nominal size (4", 5" and 6"). Or if you are just using the same graphics as a symbol for all three sizes, you could get away with just one style/definition. If one of these is the case, then you will need to move any property that is not the same for all instances to an object-based Property Set Definition. In this case, the user would then have to fill in the values and having a List Definition for each property will assure uniformity and, if you disallow values to vary from those on the list, avoid values that are not available. (No 8" fixtures; if all options are not available in all sizes or all manufacturers, then it would still be possible to select a combination of values that is not available.)
Post back with any corrections to my assumptions or if you have questions or need more detail.
David Koch
AutoCAD Architecture and Revit User
Blog | LinkedIn
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