The impact of UML documentation on software maintenance

There is an interesting article on IEEE transaction on Software engineering volume 32 June 2006 about "The impact of UML documentation on software maintenance".

The conclusions of two experiments are mostly consistent.

No savings in effort are visible.

the conclusion of the article are:
This pare presents the results of two consecutive experiemnts which have taken place in two different locations. The goal was to shed some light on the cost effectiveness of model-driven development with UML. because this is a very large area of ivestigaiton, we focused on whether models help software engineers to make quicker and better changes to existing systems. It is very ocmmon in practice to have software engineers making changes to systems they have not developed and maintenance consumes a large portion of the resources in typical software organisations . This why we thouht that this was an important first question to investigate , though we realize that model-driven development can be useful in many others ways(e.g. code generation). The result of our two expriments are mostly consistent. When considering only the time required to make code changes , using UML documentation does help to save effort overall. On the other hand, when including the time necessary to modify the diagrams, no savings in effort are visible. However, in term of the functional correctness of the changes, both experiments seem to indicate using UML has a significant , positive impact on the most complex tasks.

In my opinion this result reflects two importants points
1) the tools for approaching MDA are not mature , they can improve in usabilty
2) the skills for working with MDA with effectiveness are very high

what we need to lower the cost are probably some tools MDA that simplify the use of some subset of UML, so we can use "normal" people.

what you think?