Table of Contents

Create Simple Validation Rules

  • 2025-01-27
  • Greg Baldini
Applies to:
  • ❌ Tabular Editor 2
  • Tabular Editor 3 (Available since 3.25.0)
    ❌ Desktop
    ❌ Business
    ✔ Enterprise

This how-to demonstrates how to create simple predicate-based validation rules to enforce naming conventions and structural requirements. These rules are for illustrative purposes only and do not necessarily reflect hard technical requirements of either Metric Views or the Semantic Bridge.

The four rule helpers

There is a helper method for each type of Metric View object:

  • MakeValidationRuleForView - rules for the root View object
  • MakeValidationRuleForJoin - rules for Join objects
  • MakeValidationRuleForDimension - rules for Dimension objects
  • MakeValidationRuleForMeasure - rules for Measure objects

Each helper takes four parameters:

  1. name: unique identifier for the rule
  2. category: grouping for related rules
  3. message: error message when the rule is violated
  4. isInvalid: a function returning true if the object is invalid

Rule for View

Check that the Metric View version is the expected value:

var versionRule = SemanticBridge.MetricView.MakeValidationRuleForView(
    "version_check",
    "structure",
    "Metric View version must be 0.1 or 1.1",
    (view) => view.Version != "0.1" && view.Version != "1.1"
);

Rule for Metric View Join

Check that Metric View join sources use fully qualified table names (contain a dot):

var joinSourceRule = SemanticBridge.MetricView.MakeValidationRuleForJoin(
    "qualified_source",
    "structure",
    "Join source must be a fully qualified table name (e.g., `catalog.schema.table`)",
    (join) => !join.Source.Contains('.')
);

Rule for Metric View Dimension

Check that Metric View dimension names do not contain underscores:

var dimensionNameRule = SemanticBridge.MetricView.MakeValidationRuleForDimension(
    "no_underscores",
    "naming",
    "Dimension names should use spaces, not underscores",
    (dim) => dim.Name.Contains('_')
);

Rule for Metric View Measure

Check that Metric View measure expressions do not contain SELECT (to avoid accidental subqueries):

var measureExprRule = SemanticBridge.MetricView.MakeValidationRuleForMeasure(
    "no_select_subquery",
    "structure",
    "Measure expressions should not contain SELECT subqueries",
    (measure) => measure.Expr.ToUpper().Contains("SELECT")
);

Complete example

This Metric View has violations for each of the rules defined above:

// Create a Metric View with violations for each rule
SemanticBridge.MetricView.Deserialize("""
    version: 0.2
    source: sales.fact.orders
    joins:
      # joinSourceRule violation - not fully qualified
      - name: customer
        source: customer_table
        on: source.customer_id = customer.customer_id
    dimensions:
      # dimensionNameRule violations - contains underscores
      - name: product_name
        expr: source.product_name
      - name: order_date
        expr: source.order_date
      # This one is fine
      - name: Category
        expr: source.category
    measures:
      # measureExprRule violation - contains SELECT subquery
      - name: complex_calc
        expr: (SELECT MAX(price) FROM products)
      # This one is fine
      - name: total_revenue
        expr: SUM(source.revenue)
    """);

var versionRule = SemanticBridge.MetricView.MakeValidationRuleForView(
    "version_check",
    "structure",
    "Metric View version must be 0.1 or 1.1",
    (view) => view.Version != "0.1" && view.Version != "1.1"
);

var joinSourceRule = SemanticBridge.MetricView.MakeValidationRuleForJoin(
    "qualified_source",
    "structure",
    "Join source must be a fully qualified table name (e.g., `catalog.schema.table`)",
    (join) => !join.Source.Contains('.')
);

var dimensionNameRule = SemanticBridge.MetricView.MakeValidationRuleForDimension(
    "no_underscores",
    "naming",
    "Dimension names should use spaces, not underscores",
    (dim) => dim.Name.Contains('_')
);

var measureExprRule = SemanticBridge.MetricView.MakeValidationRuleForMeasure(
    "no_select_subquery",
    "structure",
    "Measure expressions should not contain SELECT subqueries",
    (measure) => measure.Expr.ToUpper().Contains("SELECT")
);

// Run validation with custom rules
var diagnostics = SemanticBridge.MetricView.Validate([
    versionRule,
    joinSourceRule,
    dimensionNameRule,
    measureExprRule
]).ToList();

// Output results
var sb = new System.Text.StringBuilder();
sb.AppendLine("CUSTOM VALIDATION RESULTS");
sb.AppendLine("-------------------------");
sb.AppendLine("");
sb.AppendLine($"Found {diagnostics.Count} issue(s):");
sb.AppendLine("");

foreach (var diag in diagnostics)
{
    sb.AppendLine($"[{diag.Severity}] {diag.Path}: {diag.Message}");
}

Output(sb.ToString());

Output:

CUSTOM VALIDATION RESULTS
-------------------------

Found 5 issue(s):

[Error] MetricView: Metric View version must be 0.1 or 1.1
[Error] MetricView.Joins['customer']: Join source must be a fully qualified table name (e.g., `catalog.schema.table`)
[Error] MetricView.Dimensions['product_name']: Dimension names should use spaces, not underscores
[Error] MetricView.Dimensions['order_date']: Dimension names should use spaces, not underscores
[Error] MetricView.Measures['complex_calc']: Measure expressions should not contain SELECT subqueries

Next steps

See also