One of the primary reasons why eXpress is good at supporting the entire life cycle development, and why the investment into modeling makes sense, is that eXpress is the only tool that takes a system level, multi-design discipline perspective to iteratively drive a design through the entire development cycle. Spreadsheets, flat models and commercial tools either force a late entry into modeling, or force the model to be rebuilt sometime during the process. The simple fact is that the investment into non-reusable modeling does not pay off.
The problem in supporting complex analyses, such as Testability, Reliability, etc. from a spreadsheet, is that spreadsheets do not handle a number of key functions required for such analyses.  In contrast, eXpress addresses these issues:

The problem in supporting complex analyses, such as Testability, Reliability, etc. from a spreadsheet, is that spreadsheets do not handle a number of key functions required for such analyses.  In contrast, eXpress addresses these issues:

• express is geared toward working with multidimensional data 
• express provides support for hierarchies
• express supports dimensional calculations 
• express offers simple ways to rearrange views 
• express separates the structure of a model from the views of that model

Spreadsheets have attempted to move in the direction to support these problems through the incorporation of pivot tables, etc. However, the fundamental limitations of the grid arrangement of data prohibits the simplicity required for analyzing the same set of data in multiple ways. The spreadsheet user is forced to reorganize the data for different analyses.

One of the most important points of the hybrid model in eXpress  is that one often models tests differently (functionally or based on failure) depending on whether you are testing nearer the system level or nearer the component level. However, there is a much more compelling reason for a hybrid model that becomes less arguable by those with competing approaches (including the spreadsheet approach). We’ve mentioned this before, but it is easily forgotten.

The earlier you are in system design, the more likely you don’t understand many of the failure modes. During conceptual trade-offs, where you have the most flexibility to make really big differences in the final supportability of the system being designed, you don’t want to be encumbered by necessarily thinking about modes of failure just to build a model. In these phases, eXpress’s functional approach allows the basic testing approach to be created, much like the ideas behind a Functional FMECA.  By “allocating” the approach and being able to assess it through purely functional tests, you can begin to understand partitioning problems, problems with visibility and isolation, etc.