80% of the requirements are clear, do you still need agile ?

Here is a project where the product owner has given a huge set of requirements. Let us say, X, Y and Z. He has given a time limit to the development team saying, you do whatever it takes but I want to see X,Y,Z at the end of one year. The team that has been following traditional waterfall model, decides to move towards agile methods. Inspite of knowing that the requirements wont change much, is it really necessary to follow Agile method ? Or just do whatever it takes to reach the goal ?

Before putting my thoughts on solutions, let me tell you that, this kind of model is mostly seen in product development companies, who already have an existing product and they are looking at enhancing them over a period of time with new versions.

Coming back to solutions:
1. First and foremost ensure that the estimations are in synch with the reality. It should not be that X,Y,Z takes 2 years to do it, and the product owner has given a deadline of 1 year. No matter what process you follow, this product would be a failure

2. Since, Product owner is not available for clarifications and collaboration on a day to day basis, one needs to identify a proxy who can make decisions on behalf of product owner

3. This sample case of product development can never follow all the values and principles of agile. But, they can certainly practice some of the core agile practices.

1. Daily Scrum meetings
2. Scrum of Scrums
3. Product Backlog --> Created initially by the product owner
4. Iteration Backlog --> Proxy making decisions during each iteration
5. Daily builds
6. Continuous integration
7. Usage of information radiators
8. Test Driven Development
9. Feature teams
10. Cross Functional teams
11. Team can work on Self organization
12. They even can have a scrum master
13. Pair programming
14. Usage of dual monitors
15. Velocity based estimation and/or any other estimation techniques

But remember, don't blame agile if you don't succeed in this kind of project environment, as agile methods needs customer collaboration. Without buy in from customers and stakeholders, don't expect agile methods to succeed.