Re-importing MS Project files

The merging of an import file to a non-empty PM3 project works on the basis of UniqueIDs. Within MS-Project, each line has both an ID – which represents order on the page, and UniqueID which uniquely represents a task within the project file, over its lifetime. So if you add a task to the end of the project then move it upwards, its ID changes but its UniqueID does not. Similarly, if you delete the latest Task, which had say, UniqueID 10, then create a new task, then the UniqueID of the new task will be 11. There will be no line with UniqueID 10 any more. Within MS-Project, you can choose to show the column UniqueID. PM3 keeps a record of the MS-Project UniqueIDs of the items it imports. This is very useful, because it means that having imported an MS-Project file into PM3, you can later change that MS-Project project and re-import it to PM3, and all the changes – in names, dates, new tasks – will merge correctly into the PM3 project, using the UniqueIDs to correlate items. So for example, if a workstream (Summary Task) in the import file has UniqueID 11, then if on import, the PM3 plan already has a workstream with MS UniqueID = 11, then that existing PM3 workstream will be updated with any properties of the imported workstream. Otherwise, PM3 will create a new workstream based on the imported workstream properties and record the MS UniqueID against the PM3 plan. Caveat – for each PM3 plan, only import files from one MS-Project project. If you try to import files from 2 different MS-Project files into the one PM3 project, there will usually be a mis-match of UniqueIDs. This is because UniqueIDs are unique only to an individual MS-Project project. Two different MS-Project projects will almost certainly have the same UniqueID numbers, but of course representing completely different tasks.