Powerbi Review Semantic Model

Warning: This skill is incomplete and still in progress, but may provide value already as-is -- Kurt

Reviewing Semantic Models

Structured evaluation of Power BI semantic models against quality, performance, and best practice standards. Produces actionable findings with prioritized recommendations.

Review Workflow

Step 0: Gather Context

Before analyzing TMDL, collect metadata and understand the business context.

Run the model info script:

python3 scripts/get_model_info.py -w <workspace-id> -m <model-id>

This returns: storage mode, model size, connected reports, deployment pipeline, endorsement status, sensitivity label, data sources, refresh schedule, last refresh, and capacity SKU.

Ask the user:

• What business process does this model represent?
• Who are the primary consumers? (report developers, analysts, executives, AI/Copilot users?)
• Are they the developer of both the model and its reports, or only one?
• Is the model in development, testing, or production?
• Where should findings be documented? (scratchpad, agent-docs, wiki, etc.)

Understanding the business context is critical. A model for 3 analysts has different requirements than one consumed by Copilot across the organization. The audit categories and their severity shift based on this context.

Step 1: Analyze Model Structure

Inspect the model definition to evaluate its structure. The approach depends on available tooling -- use whatever is available to read the model's tables, columns, measures, relationships, and expressions. Do not prescribe a specific tool; common options include Tabular Editor, the te-cli, fab export to TMDL, or programmatic access via APIs.

Step 2: Audit Categories

Evaluate findings across categories, ordered by severity:

Critical

• Bidirectional relationships (ambiguity risk)
• Circular dependencies between tables
• Missing data types on columns
• Tables without relationships (orphaned)

Memory and Size

• High-cardinality columns with large dictionaries (GUIDs, transaction IDs, composite keys)
• IsAvailableInMdx enabled on hidden or high-cardinality columns (wastes memory on attribute hierarchies unused by DAX; disable for columns not consumed via Analyze in Excel / MDX)
• Unsplit DateTime columns (near-unique precision creating massive dictionaries)
• Auto Date/Time tables (hidden LocalDateTable_* bloating memory)
• Inappropriate data types (Double for currency, String for numeric)
• Calculated columns that could be measures
• Unused columns or tables (no references in measures or visuals or other downstream items)

Data Reduction

• Unfiltered history in fact tables (no date-range filter or incremental refresh)
• Columns that aren't necessary for reporting or calculations or consumption
• Pre-summarization opportunities (detail grain not needed for reporting)
• Columns better handled upstream (i.e. calculations not done in calc columns or PQ)

DAX Anti-Patterns (for systematic DAX query optimization, use the dax skill)

• Filtering tables instead of columns in CALCULATE (causes both correctness and performance issues)
• Unhandled division by zero (use DIVIDE() or explicit zero-check; note: plain / is fine when the denominator is guaranteed non-zero and can be faster)
• Iterators with callbacks or nested iterators over large tables (use aggregators like SUM/AVERAGE when possible; iterators over large tables are fine if the expression is Storage Engine-pushable)
• Missing KEEPFILTERS around non-equality filter predicates in CALCULATE

Measure Hygiene

• Implicit measures used where explicit measures should exist
• Report-scoped extension measures that should be model-level
• Duplicate or overlapping measures with ambiguous names

Documentation

• Tables or columns missing descriptions
• Missing display folders for measures
• Inconsistent naming conventions (use the standardize-naming-conventions skill)

Design

• Star schema violations (direct fact-to-fact relationships, snowflake patterns)
• Missing or misconfigured date table: must be marked (dataCategory: Time in TMDL, with a key Date column), have continuous daily dates (no gaps), span the full range of fact data, and relate to fact tables via a single-column relationship. Missing any of these causes time intelligence functions (DATEADD, SAMEPERIODLASTYEAR, TOTALYTD) to return BLANK
• Excessive columns per table (>30 suggests denormalization issues)
• Many-to-many relationships without bridging tables
• Multiple fact tables relating to the same dimension via different keys without a shared conformed dimension (causes slicers on one fact to not filter the other)
• Inactive relationships without corresponding USERELATIONSHIP in measures (orphaned relationships that suggest incomplete modeling)

Direct Lake (if applicable)

• Delta table health (parquet file count, V-Order, row group sizes)
• DirectQuery fallback risk (RLS definitions, SQL endpoint views)

AI and Copilot Readiness (see references/ai-readiness.md)

• Duplicate field names across tables (confuses Copilot/data agents)
• Missing AI instructions
• Missing or inadequate descriptions for AI consumption
• Complex patterns (disconnected tables, many-to-many, inactive relationships) are valid model design but AI may struggle with them

Step 3: Performance Analysis

For performance-specific analysis, see references/performance.md.

Step 4: Report Findings

Produce a structured markdown report with:

• Summary table of finding counts by severity
• Detailed findings with file locations and line numbers where possible
• Specific remediation recommendations for each finding
• Prioritized action list (critical first)

Using the Semantic Model Reviewer Agent

Dispatch the semantic-model-auditor agent to perform the structural audit. The agent handles export, analysis, and reporting autonomously.

Notes

• The structural audit analyzes model metadata -- it does not execute DAX queries or check data quality
• For DAX query performance testing, see references/performance.md
• For DAX optimization, use the dax skill
• For companion report review, use the review-report skill in the reports plugin

References

• references/ai-readiness.md -- Copilot/Data Agent preparation: AI instructions, descriptions, schema, verified answers
• references/performance.md -- Performance testing methodology, unused column detection, memory analysis
• scripts/get_model_info.py -- Quick model metadata overview (storage mode, size, reports, pipeline, endorsement, data sources)

Related Skills

• dax -- DAX performance optimization
• review-report (reports plugin) -- Companion skill for report-level review
• standardize-naming-conventions -- Naming audit and remediation
• lineage-analysis -- Downstream report discovery
• refresh-semantic-model -- Refresh monitoring and troubleshooting