I would like to introduce the one of new feature in Map 3D 2009. The command is called "mapfeaturesplit" & "mapfeaturemerge". It able to split/ merge feature data seamlessly and provides the tools called "split & merge rules" to handling the data attribute for those data objects.

There is two options if you do mapfeaturesplit:
1 - It supports all AutoCAD command for snapping feature object when you doing the split feature object action. You can precisely snap the object and split the object.
2 - It can be based on the existing line entity to split the object.

Step for doing split
1 - Connect to feature data
2 - Open feature data table
3 - Key-in command "mapfeaturesplit"
4 - Select feature to edit
5 - Select Draw a new line
6 - Feature object divided to two objects
7 - Check-in feature

Step for doing merge
1 - Key-in command "mapfeaturemerge"
2 - Select features to merge
3 - Specify feature ID for use
4 - Feature merged
5 - Check-in feature

You can design a Split or merge rules first, and then all attributes will be based on those rules to split or merge the objects. It's quite useful. In case, if the attribute is the unique ID, this is not possible to copy the existing ID for the new object. Good to try!