Living In A Typeless Model: We’re Not Talking About Voice Commands

If Susan told her son, Eddie, to buy 10 Granny Smith Apples that each weigh 12 ounces for Grandma Jane’s Perfect Apple Pie recipe, she is asking for ten 12 ounce Instances of a Type of Granny Smith Apple.  Because Eddie heard her wrong, he bought 10 Red Delicious Apples of various sizes from 8 to 14 ounces.  He got the wrong Type of Apples and the Instance size of each apple was only affecting that specific apple.  That is a general idea of what Type and Instance are referring to in Revit.  A Type Property applies to all elements and changing the value in one will change that value in all occurrences.  An Instance Property applies only to the one element and directly changing the value does not affect other instances.

  

Using Type Properties may sound like an advantage, but what if Susan wanted to change the recipe and provide 5 Granny Smith and 5 Red Delicious.  If you changed the Type information for one Apple, it would alter all the Apples and there is no way to prevent that as long as the Apple selection is a Type property.  If you were to change the Type Property of the Apple to an Instance Property, then half of the apples could be changed independently.  The question then becomes what if we have 100 Apples and need to edit some of them.  Do I need to individually edit each instance?  The complex answer to that is simply No!

Instance properties can be edited in groups through schedules.  Obviously, the parameter being used must be available in a schedule.  In this case, Susan decided to only change the 14 ounce apples back to Granny Smith.  In the schedule for Apples, sort by the Weight and uncheck the requirement to ‘Itemize every Instance’.  This is referred to as collapsing a schedule.  Every instance of the Apple is now represented in a common line by the corresponding weight and changing the parameter value will edit every instance simultaneously that is represented in that line.  When the edit is done, the schedule can be expanded by checking the ‘Itemize every Instance’ box.  Sort by Mark and see what the single edit did for Grandma Jane’s recipe with Susan’s twist.  By facilitating as many parameters as possible with Instance Parameters rather than Type-based parameters, users have more flexibility in manipulating data throughout a model.  

One interesting fact to note, Instance-based equation results can contain type-based parameters.  Type-based equation results cannot contain instance-based parameters.  Varying values of a parameter cannot logically provide the same result in an equation.  Using Instance-based parameters for results will free up the potential for information and make it easier to obtain logical equations that work.  We’ll get deeper into that next time.

-Craig
www.ModelingDynamics.net

DISCLAIMER: All names appearing in this post are fictitious. Any resemblance to real persons, living or dead, is purely coincidental.