Check out Craig Utley’s presentation, “Basics 104 – Why BI Projects Fail (and what you can do about it)“.
This is one presentation of a series of SSAS Multidimensional presentations I found very valuable. They were originally hosted at LearnMicrosoftBI which is now retired, but all of the videos are now on YouTube. Here’s the master video list.
Business Intelligence Semantic Model (BISM) Architecture 
(I obtained this from some Microsoft site; I was not the original creator)
Decision: Multidimensional v. Tabular Models
Tools for Tabular Data Model Developers
Some resources from the archives…
MSDN: Introduction to Cubes  | Nice introduction and sample cube diagram. Defines Facts, Measures, Dimensions, Aggregates, Hierarchies, and more. |
Multidimensional resources
Key Concepts in MDX (Analysis Services)
Multidimensional Expressions (MDX) Reference