There appears to be a bit of split in the use of terminology in defining the scope of a project through the creation of the Work Breakdown Structure. Some seem to take an activities-based view, as evidenced by the template on this site called Project Work Breakdown Structure Guidelines, while others seem to take a deliverables-based approach, as found in PMI's Guidleine to the Project Management Body of Knowledge, which says that creating a WBS is the process of "... subdividing project deliverables and project work into smaller, more manageable components". Still others take a hap-hazard approach - don't worry - we won't talk about that here.
I have long held that a deliverables-based approach to project planning, executing and, most importantly, progress tracking and reporting is key to creating a mindset on a project that focuses not on what you have done (the "activity"), but on what you have produced (the "deliverable"). Have you seen status reports that focus on activities done last period, and activities planned for next period? Are they effective? How about status reports that delve into what was produced last period and what is planned to be produced next period? See the difference? One pulls you down into the whirlpool of things people did, often with no relation to why they did these things and what they hoped to accomplish. The other is much more concrete - what you produced in relation to the project WBS. You can even get very black and white about these things using the done/not done approach - a given deliverable is done, or it is not done - 0% Complete or 100% Complete. Of course, this doesn't work very well with ill-formed project schedules where a deliverable can consume many months or even years of effort. But if deliverables are concise, well defined and restricted to maximum effort levels, it works very well. Or you can consider breaking large deliverables into work products, the "done/not done" of which determine an overall %Complete, and track your deliverables that way.
If you consider a deliverable to be the output of an activity, why not flip it around and relegate activities to those things you must do to produce a deliverable? You can structure your project schedule around deliverables, and you can measure your progress based on the deliverables you have produced, or the portion of a deliverable you have produced. This ties in very nicely to Earned Value Management, but that is another topic.
How do you define the scope of your project? Are you an Activities-based or a Deliverables-based thinker? Do you measure progress based on what your team did for a period of time? Or on what they produced?