I am sometimes being asked by customers what to make of how some vendors (or those who have been educated by those vendors) are describing capabilities of their software with regard to support for Office file formats:

compatibility claims

(I am not making these up, you can find links to sources at the end of this post.)

Now, apparently the assertions of "support for file formats" or "compatibility" leave some room for interpretation:
Opening a PowerPoint deck in Impress 3.2

I was a bit disappointed about changes in this simple (5 minutes to create) PowerPoint presentation (3 slides) that I opened in the current version 3.2 of OpenOffice.org (upon which IBM Lotus Symphony version 3 is going to be based, according to IBM).

Being technically minded, I didn't give up and tried to understand if there was a deeper reason why the presentation changed so much (by the way, the bulleted list on slide 3 didn't get deleted in Impress, it's just rendered "invisible" as white text on white background).

Here's one big and obvious difference between PowerPoint and OpenOffice.org that I found and that could explain some of what had happened to my document (be aware that this represents what I could gather about the functionality in OpenOffice.org by looking at the user interface, so no guarantees that the document engine uses the same representation):

Slide architecture in PowerPoint and Impress

Every slide in PowerPoint is connected to a specific layout that is contained in what is called a "Slide Master", and each layout then can have additional formatting, content placeholders or backgrounds.

In OpenOffice.org Impress, on the other hand, "Master Pages" with text styles and backgrounds are not linked to layouts and Impress doesn't allow the user to create custom layouts (it comes with a set of predefined ones).

This leads to a near-total loss of information about the original slide masters in PowerPoint when importing .ppt(x) files into Impress, something that becomes especially apparent after round-tripping (re-exporting) the presentation from Impress back to PowerPoint (using the PPT format, as PPTX is currently not supported for export):

PPT Impress round trip

As far as I can tell from looking at this example, here are some of the things that happen in this process:

  1. Import (PowerPoint to Impress)
    1. Impress creates a new unique "Master Page" for each slide
    2. there are issues if a PowerPoint master makes use of custom layouts that are not identical to the default layouts in Impress (loss of slide elements and formatting)
    3. custom layouts cannot be imported as they don't exist in Impress
    4. Impress is confused about some placeholder text on the Slide Masters that gets imported as literal text (also, since the layout changes randomly, in some cases that placeholder text could be displayed on top of other content)
  2. Export (Impress to PowerPoint)
    1. Impress creates a new unique "Slide Master" for each slide
    2. every Slide Master gets a full complement of all default Impress slide layouts
    3. some style changes can happen

It seems that there are additional limitations to consider, unfortunately I wasn't able to find an explanation or documentation on best practices or workarounds: When I tried to work with a PowerPoint presentation that contained 7 Slide Masters and brought that over into Impress, additional changes could be observed after saving as .ODP and subsequently reopening the deck:
 
Impress 3.2 save as ODP and reopen file
 
Based on these observations, I suspect that fundamental differences between PowerPoint and Impress are responsible for much of the visible behavior; thus to adress these issues, it would not help to only improve the implementation quality of the file conversion code in OpenOffice.org.
 
This would imply that without a major rearchitecture of either Impress or PowerPoint to make one more similar to the other, it would be hard to conceive a way to preserve full fidelity in round-tripping documents as the feature set of the applications is not able to fully express fundamental properties of their "partner" application. By the way, as a long time OpenOffice.org user (20+ years, feeling really old now!) I can tell you that some functionality like paragraph styles in Impress has no equivalent in PowerPoint, so it would be unfair to say that conversion challenges only exist on one end.
 
Actually, the list of differences that go beyond the file format of choice is quite long and available when you "save as ..." using ODF from the Office 2010 applications (if you haven't yet installed that, here's a direct web link that you can use).
 
Is there a happy ending? Well ... here is the best way that I found to deal with the example above. Please note that you will have to sacrifice some of the editability of the file, so the solution is really most useful for a one time handover and will not satisfy all the typical requirements in an ongoing co-authoring scenario using different products (because of the differences in product architecture):
Here's what the example presentation looks like when saved from Office 2010 in the .odp file format and opened with OpenOffice.org 3.2 (please note the clever use of Master Pages to "flatten" the relationship between slide masters and custom layouts in PowerPoint and thus preserve great fidelity):
Impress showing PowerPoint 2010 ODF export
 
Even the placeholder text functions correctly as placeholder. Good job (if I am allowed to say so)!
 
I hope this was of some interest to you, it certainly helps to appreciate the efforts that are being made on achieving some degree of interoperability, while illustrating that compatibility is not a simple tick in the box that some vendors would want to make you believe it was. 
 
 
Sources for compatibility claims