RPDbeginner
RPD Three-Layer Architecture
Explain the Physical, Business Model & Mapping (BMM), and Presentation layers that make up the OBIEE repository and why the separation matters.
The RPD (repository) is the single artifact that makes OBIEE's semantic layer possible, and its three-layer design is the most foundational concept in the entire product — almost every OBIEE interview opens here. Getting this crisp and confident signals real hands-on experience.
It's like a restaurant menu (Presentation layer) that lists "Grandma's Roast Chicken" — simple and appealing — while the recipe card (BMM layer) defines the actual technique and ingredients, and the walk-in fridge inventory (Physical layer) tracks the raw chicken, herbs, and vegetables exactly as delivered.
Key Concepts
1
The Physical layer mirrors the actual data sources: physical tables, columns, keys, joins, and connection pools exactly as they exist in the source database(s) — including quirks like non-standard join conditions or multiple physical sources for the same conceptual table (used later for aggregate navigation and fragmentation). The Business Model and Mapping (BMM) layer is where the real modeling work happens: physical tables are mapped into logical dimension and fact tables, logical joins are defined (independent of physical join syntax), calculated/derived logical columns are built, and hierarchies and levels are defined for drill-down and aggregate navigation. The Presentation layer is the thin, business-user-facing layer — it exposes a curated, renamed, reorganized subset of the BMM as "subject areas," "presentation tables," and "presentation columns" that end users interact with in Answers/Analyses.
Physical layerBusiness Model and Mapping (BMM) layerPresentation layer
2
The separation exists so that changes ripple in a controlled direction: you can change a physical table's underlying join or add a new data source without necessarily touching what business users see, and you can reorganize or rename what's presented without altering the underlying logical model. It's also what enables one BMM to expose multiple differently-named/organized presentation catalogs for different audiences.
3
Interviewers often probe this by asking you to trace what happens when a column is renamed at each layer, or why a physical layer join error can break a dashboard that "never touched" the physical layer directly — a good answer walks the dependency chain physical → BMM → presentation.