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ArxCafe / ML Engineering / Layer 0
Book 0
Google Professional Machine Learning Engineer

Layer 0 — Mathematical & Statistical Foundations (Bedrock)

This layer explains the learning objective beneath every supervised ML system: expected loss minimization under uncertainty. Everything above this layer is engineering around the gap between what we want (real-world performance) and what we can optimize (training-set performance).
Why This Layer Exists

In arxcafe, a “book” is not one giant page. It is a network (graph) of atomic concept pages. Each concept is linkable, searchable, and reusable across multiple layers.

Core Claim

Machine learning is the art of minimizing the wrong objective in a controlled way.

Layer 0 gives you the language to explain why models work when they work, and why they break when they break.

What This Layer Enables
  • Reason about generalization (why training success doesn’t guarantee production success)
  • Explain overfitting without buzzwords
  • Choose losses/metrics intentionally (success is defined, not discovered)
  • Predict failures under distribution shift and data drift
What Breaks If Skipped
  • “Model selection” becomes trial-and-error rather than reasoning
  • Monitoring and retraining feel optional instead of inevitable
  • Offline metrics get mistaken for business outcomes
arxcafe Implementation Plan (Summary)
  • Layer (Book) → folder namespace (e.g., /ml-engineering/layer-0/)
  • Part (Section) → section index page
  • Concept (Topic) → atomic HTML page using a consistent template
  • No monolithic book.html; the “book” is the table-of-contents plus interlinked pages