Schema Validation for Construction Data

Overview

Validate data structures against defined schemas for construction data exchange. Ensure API payloads, file imports, and BIM exports conform to expected formats before processing.

Schema Validation Framework

Core Schema Validator

python
from dataclasses import dataclass, field
from typing import Any, Dict, List, Optional, Union
from enum import Enum
import json
import re
from datetime import datetime

class SchemaType(Enum):
    STRING = "string"
    NUMBER = "number"
    INTEGER = "integer"
    BOOLEAN = "boolean"
    ARRAY = "array"
    OBJECT = "object"
    DATE = "date"
    DATETIME = "datetime"
    CSI_CODE = "csi_code"
    CURRENCY = "currency"
    GUID = "guid"

@dataclass
class SchemaField:
    name: str
    type: SchemaType
    required: bool = True
    nullable: bool = False
    min_value: Optional[float] = None
    max_value: Optional[float] = None
    min_length: Optional[int] = None
    max_length: Optional[int] = None
    pattern: Optional[str] = None
    enum_values: Optional[List[Any]] = None
    items_schema: Optional['Schema'] = None  # For arrays
    properties: Optional[Dict[str, 'SchemaField']] = None  # For objects
    description: str = ""

@dataclass
class Schema:
    name: str
    version: str
    fields: Dict[str, SchemaField]
    description: str = ""

@dataclass
class SchemaValidationError:
    path: str
    message: str
    expected: str
    actual: Any

@dataclass
class SchemaValidationResult:
    is_valid: bool
    errors: List[SchemaValidationError] = field(default_factory=list)
    schema_name: str = ""
    schema_version: str = ""

    def add_error(self, path: str, message: str, expected: str, actual: Any):
        self.errors.append(SchemaValidationError(path, message, expected, actual))
        self.is_valid = False

    def to_report(self) -> str:
        lines = [
            f"Schema Validation: {self.schema_name} v{self.schema_version}",
            "=" * 50,
            f"Status: {'✓ VALID' if self.is_valid else '✗ INVALID'}",
            f"Errors: {len(self.errors)}",
            ""
        ]

        for error in self.errors:
            lines.append(f"❌ {error.path}")
            lines.append(f"   {error.message}")
            lines.append(f"   Expected: {error.expected}")
            lines.append(f"   Actual: {error.actual}")
            lines.append("")

        return "\n".join(lines)


class SchemaValidator:
    """Validate data against schemas."""

    # Custom type patterns
    PATTERNS = {
        SchemaType.CSI_CODE: r'^\d{2}\s?\d{2}\s?\d{2}$',
        SchemaType.GUID: r'^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$',
        SchemaType.CURRENCY: r'^-?\d+(\.\d{2})?$',
        SchemaType.DATE: r'^\d{4}-\d{2}-\d{2}$',
        SchemaType.DATETIME: r'^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}',
    }

    def validate(self, data: Any, schema: Schema) -> SchemaValidationResult:
        result = SchemaValidationResult(
            is_valid=True,
            schema_name=schema.name,
            schema_version=schema.version
        )

        self._validate_object(data, schema.fields, "", result)
        return result

    def _validate_object(self, data: Any, fields: Dict[str, SchemaField], path: str, result: SchemaValidationResult):
        if not isinstance(data, dict):
            result.add_error(path or "root", "Expected object", "object", type(data).__name__)
            return

        # Check required fields
        for field_name, field_schema in fields.items():
            field_path = f"{path}.{field_name}" if path else field_name

            if field_name not in data:
                if field_schema.required:
                    result.add_error(field_path, "Required field missing", "present", "missing")
                continue

            value = data[field_name]

            # Check nullable
            if value is None:
                if not field_schema.nullable:
                    result.add_error(field_path, "Field cannot be null", "non-null", "null")
                continue

            # Validate type
            self._validate_field(value, field_schema, field_path, result)

        # Check for extra fields (warning only)
        for key in data.keys():
            if key not in fields:
                # Could add warning here if needed
                pass

    def _validate_field(self, value: Any, schema: SchemaField, path: str, result: SchemaValidationResult):
        # Type validation
        if not self._check_type(value, schema.type):
            result.add_error(path, f"Invalid type", schema.type.value, type(value).__name__)
            return

        # String validations
        if schema.type == SchemaType.STRING:
            if schema.min_length and len(value) < schema.min_length:
                result.add_error(path, f"String too short", f"min {schema.min_length}", len(value))
            if schema.max_length and len(value) > schema.max_length:
                result.add_error(path, f"String too long", f"max {schema.max_length}", len(value))
            if schema.pattern and not re.match(schema.pattern, value):
                result.add_error(path, "Pattern mismatch", schema.pattern, value)

        # Numeric validations
        if schema.type in (SchemaType.NUMBER, SchemaType.INTEGER):
            if schema.min_value is not None and value < schema.min_value:
                result.add_error(path, "Value below minimum", f">= {schema.min_value}", value)
            if schema.max_value is not None and value > schema.max_value:
                result.add_error(path, "Value above maximum", f"<= {schema.max_value}", value)

        # Enum validation
        if schema.enum_values and value not in schema.enum_values:
            result.add_error(path, "Invalid enum value", str(schema.enum_values), value)

        # Array validation
        if schema.type == SchemaType.ARRAY and schema.items_schema:
            for i, item in enumerate(value):
                item_path = f"{path}[{i}]"
                if schema.items_schema.fields:
                    self._validate_object(item, schema.items_schema.fields, item_path, result)

        # Nested object validation
        if schema.type == SchemaType.OBJECT and schema.properties:
            self._validate_object(value, schema.properties, path, result)

        # Custom type validation
        if schema.type in self.PATTERNS:
            pattern = self.PATTERNS[schema.type]
            if not re.match(pattern, str(value)):
                result.add_error(path, f"Invalid {schema.type.value} format", pattern, value)

    def _check_type(self, value: Any, expected: SchemaType) -> bool:
        type_checks = {
            SchemaType.STRING: lambda v: isinstance(v, str),
            SchemaType.NUMBER: lambda v: isinstance(v, (int, float)),
            SchemaType.INTEGER: lambda v: isinstance(v, int) and not isinstance(v, bool),
            SchemaType.BOOLEAN: lambda v: isinstance(v, bool),
            SchemaType.ARRAY: lambda v: isinstance(v, list),
            SchemaType.OBJECT: lambda v: isinstance(v, dict),
            SchemaType.DATE: lambda v: isinstance(v, str),
            SchemaType.DATETIME: lambda v: isinstance(v, str),
            SchemaType.CSI_CODE: lambda v: isinstance(v, str),
            SchemaType.CURRENCY: lambda v: isinstance(v, (int, float, str)),
            SchemaType.GUID: lambda v: isinstance(v, str),
        }
        return type_checks.get(expected, lambda v: True)(value)

Construction Data Schemas

Cost Estimate Schema

python
# Define schema for cost estimate data
COST_ESTIMATE_SCHEMA = Schema(
    name="CostEstimate",
    version="1.0",
    description="Schema for construction cost estimates",
    fields={
        "project_id": SchemaField(
            name="project_id",
            type=SchemaType.STRING,
            required=True,
            description="Unique project identifier"
        ),
        "project_name": SchemaField(
            name="project_name",
            type=SchemaType.STRING,
            required=True,
            max_length=200
        ),
        "estimate_type": SchemaField(
            name="estimate_type",
            type=SchemaType.STRING,
            required=True,
            enum_values=["conceptual", "schematic", "design_development", "construction_documents", "bid"]
        ),
        "estimate_date": SchemaField(
            name="estimate_date",
            type=SchemaType.DATE,
            required=True
        ),
        "currency": SchemaField(
            name="currency",
            type=SchemaType.STRING,
            required=False,
            enum_values=["USD", "EUR", "GBP", "CAD"],
            nullable=True
        ),
        "gross_area": SchemaField(
            name="gross_area",
            type=SchemaType.NUMBER,
            required=True,
            min_value=0,
            description="Gross floor area in SF or SM"
        ),
        "line_items": SchemaField(
            name="line_items",
            type=SchemaType.ARRAY,
            required=True,
            items_schema=Schema(
                name="LineItem",
                version="1.0",
                fields={
                    "id": SchemaField(name="id", type=SchemaType.STRING, required=True),
                    "csi_code": SchemaField(name="csi_code", type=SchemaType.CSI_CODE, required=False, nullable=True),
                    "description": SchemaField(name="description", type=SchemaType.STRING, required=True, max_length=500),
                    "quantity": SchemaField(name="quantity", type=SchemaType.NUMBER, required=True, min_value=0),
                    "unit": SchemaField(name="unit", type=SchemaType.STRING, required=True),
                    "unit_cost": SchemaField(name="unit_cost", type=SchemaType.NUMBER, required=True, min_value=0),
                    "amount": SchemaField(name="amount", type=SchemaType.NUMBER, required=True, min_value=0),
                }
            )
        ),
        "subtotal": SchemaField(
            name="subtotal",
            type=SchemaType.NUMBER,
            required=True,
            min_value=0
        ),
        "contingency_percent": SchemaField(
            name="contingency_percent",
            type=SchemaType.NUMBER,
            required=False,
            min_value=0,
            max_value=50
        ),
        "total": SchemaField(
            name="total",
            type=SchemaType.NUMBER,
            required=True,
            min_value=0
        )
    }
)

Schedule Data Schema

python
SCHEDULE_SCHEMA = Schema(
    name="ProjectSchedule",
    version="1.0",
    description="Schema for project schedule data",
    fields={
        "project_id": SchemaField(name="project_id", type=SchemaType.STRING, required=True),
        "schedule_name": SchemaField(name="schedule_name", type=SchemaType.STRING, required=True),
        "data_date": SchemaField(name="data_date", type=SchemaType.DATE, required=True),
        "start_date": SchemaField(name="start_date", type=SchemaType.DATE, required=True),
        "finish_date": SchemaField(name="finish_date", type=SchemaType.DATE, required=True),
        "calendar": SchemaField(
            name="calendar",
            type=SchemaType.STRING,
            required=False,
            enum_values=["5-day", "6-day", "7-day"],
            nullable=True
        ),
        "tasks": SchemaField(
            name="tasks",
            type=SchemaType.ARRAY,
            required=True,
            items_schema=Schema(
                name="Task",
                version="1.0",
                fields={
                    "id": SchemaField(name="id", type=SchemaType.STRING, required=True),
                    "wbs": SchemaField(name="wbs", type=SchemaType.STRING, required=False, nullable=True),
                    "name": SchemaField(name="name", type=SchemaType.STRING, required=True, max_length=300),
                    "start_date": SchemaField(name="start_date", type=SchemaType.DATE, required=True),
                    "finish_date": SchemaField(name="finish_date", type=SchemaType.DATE, required=True),
                    "duration": SchemaField(name="duration", type=SchemaType.INTEGER, required=True, min_value=0),
                    "percent_complete": SchemaField(name="percent_complete", type=SchemaType.NUMBER, required=False, min_value=0, max_value=100),
                    "predecessors": SchemaField(name="predecessors", type=SchemaType.ARRAY, required=False, nullable=True),
                    "resources": SchemaField(name="resources", type=SchemaType.ARRAY, required=False, nullable=True),
                }
            )
        )
    }
)

BIM Element Schema

python
BIM_ELEMENT_SCHEMA = Schema(
    name="BIMElement",
    version="1.0",
    description="Schema for BIM element data",
    fields={
        "guid": SchemaField(name="guid", type=SchemaType.GUID, required=True),
        "ifc_class": SchemaField(
            name="ifc_class",
            type=SchemaType.STRING,
            required=True,
            pattern=r'^Ifc[A-Z][a-zA-Z]+$'
        ),
        "name": SchemaField(name="name", type=SchemaType.STRING, required=False, nullable=True),
        "description": SchemaField(name="description", type=SchemaType.STRING, required=False, nullable=True),
        "level": SchemaField(name="level", type=SchemaType.STRING, required=False, nullable=True),
        "classification": SchemaField(
            name="classification",
            type=SchemaType.OBJECT,
            required=False,
            nullable=True,
            properties={
                "system": SchemaField(name="system", type=SchemaType.STRING, required=True),
                "code": SchemaField(name="code", type=SchemaType.STRING, required=True),
                "name": SchemaField(name="name", type=SchemaType.STRING, required=False, nullable=True),
            }
        ),
        "quantities": SchemaField(
            name="quantities",
            type=SchemaType.OBJECT,
            required=False,
            nullable=True,
            properties={
                "area": SchemaField(name="area", type=SchemaType.NUMBER, required=False, min_value=0, nullable=True),
                "volume": SchemaField(name="volume", type=SchemaType.NUMBER, required=False, min_value=0, nullable=True),
                "length": SchemaField(name="length", type=SchemaType.NUMBER, required=False, min_value=0, nullable=True),
                "count": SchemaField(name="count", type=SchemaType.INTEGER, required=False, min_value=0, nullable=True),
            }
        ),
        "properties": SchemaField(name="properties", type=SchemaType.OBJECT, required=False, nullable=True)
    }
)

RFI Schema

python
RFI_SCHEMA = Schema(
    name="RFI",
    version="1.0",
    description="Schema for Request for Information",
    fields={
        "rfi_number": SchemaField(name="rfi_number", type=SchemaType.STRING, required=True, pattern=r'^RFI-\d+$'),
        "project_id": SchemaField(name="project_id", type=SchemaType.STRING, required=True),
        "subject": SchemaField(name="subject", type=SchemaType.STRING, required=True, max_length=500),
        "status": SchemaField(
            name="status",
            type=SchemaType.STRING,
            required=True,
            enum_values=["draft", "submitted", "in_review", "answered", "closed"]
        ),
        "priority": SchemaField(
            name="priority",
            type=SchemaType.STRING,
            required=False,
            enum_values=["low", "medium", "high", "critical"],
            nullable=True
        ),
        "date_submitted": SchemaField(name="date_submitted", type=SchemaType.DATE, required=True),
        "date_required": SchemaField(name="date_required", type=SchemaType.DATE, required=True),
        "from_company": SchemaField(name="from_company", type=SchemaType.STRING, required=True),
        "to_company": SchemaField(name="to_company", type=SchemaType.STRING, required=True),
        "spec_section": SchemaField(name="spec_section", type=SchemaType.CSI_CODE, required=False, nullable=True),
        "drawing_reference": SchemaField(name="drawing_reference", type=SchemaType.STRING, required=False, nullable=True),
        "question": SchemaField(name="question", type=SchemaType.STRING, required=True),
        "response": SchemaField(name="response", type=SchemaType.STRING, required=False, nullable=True),
        "date_responded": SchemaField(name="date_responded", type=SchemaType.DATE, required=False, nullable=True),
        "attachments": SchemaField(name="attachments", type=SchemaType.ARRAY, required=False, nullable=True)
    }
)

Schema Registry

python
class ConstructionSchemaRegistry:
    """Registry of construction data schemas."""

    def __init__(self):
        self.schemas: Dict[str, Schema] = {}
        self._register_defaults()

    def _register_defaults(self):
        self.register(COST_ESTIMATE_SCHEMA)
        self.register(SCHEDULE_SCHEMA)
        self.register(BIM_ELEMENT_SCHEMA)
        self.register(RFI_SCHEMA)

    def register(self, schema: Schema):
        key = f"{schema.name}:{schema.version}"
        self.schemas[key] = schema
        # Also register without version for latest
        self.schemas[schema.name] = schema

    def get(self, name: str, version: str = None) -> Optional[Schema]:
        if version:
            return self.schemas.get(f"{name}:{version}")
        return self.schemas.get(name)

    def validate(self, data: Any, schema_name: str, version: str = None) -> SchemaValidationResult:
        schema = self.get(schema_name, version)
        if not schema:
            result = SchemaValidationResult(is_valid=False)
            result.add_error("schema", f"Schema '{schema_name}' not found", "valid schema", "not found")
            return result

        validator = SchemaValidator()
        return validator.validate(data, schema)

    def list_schemas(self) -> List[str]:
        return [k for k in self.schemas.keys() if ':' in k]

Usage Examples

python
# Initialize registry
registry = ConstructionSchemaRegistry()

# Validate cost estimate
estimate_data = {
    "project_id": "PROJ-001",
    "project_name": "Downtown Office Tower",
    "estimate_type": "schematic",
    "estimate_date": "2026-01-15",
    "gross_area": 50000,
    "line_items": [
        {
            "id": "1",
            "csi_code": "03 30 00",
            "description": "Cast-in-place concrete",
            "quantity": 5000,
            "unit": "CY",
            "unit_cost": 150.00,
            "amount": 750000.00
        }
    ],
    "subtotal": 750000.00,
    "contingency_percent": 10,
    "total": 825000.00
}

result = registry.validate(estimate_data, "CostEstimate")
print(result.to_report())

# Validate RFI
rfi_data = {
    "rfi_number": "RFI-042",
    "project_id": "PROJ-001",
    "subject": "Concrete mix design clarification",
    "status": "submitted",
    "priority": "high",
    "date_submitted": "2026-01-20",
    "date_required": "2026-01-27",
    "from_company": "ABC Concrete",
    "to_company": "XYZ Architects",
    "spec_section": "03 30 00",
    "question": "Please clarify the required PSI for the foundation pour."
}

result = registry.validate(rfi_data, "RFI")
if result.is_valid:
    print("RFI data is valid")
else:
    print(result.to_report())

JSON Schema Export

python
def export_to_json_schema(schema: Schema) -> dict:
    """Export DDC schema to JSON Schema format."""

    def field_to_json_schema(field: SchemaField) -> dict:
        type_map = {
            SchemaType.STRING: "string",
            SchemaType.NUMBER: "number",
            SchemaType.INTEGER: "integer",
            SchemaType.BOOLEAN: "boolean",
            SchemaType.ARRAY: "array",
            SchemaType.OBJECT: "object",
            SchemaType.DATE: "string",
            SchemaType.DATETIME: "string",
            SchemaType.CSI_CODE: "string",
            SchemaType.CURRENCY: "number",
            SchemaType.GUID: "string",
        }

        js = {"type": type_map.get(field.type, "string")}

        if field.description:
            js["description"] = field.description
        if field.min_value is not None:
            js["minimum"] = field.min_value
        if field.max_value is not None:
            js["maximum"] = field.max_value
        if field.min_length is not None:
            js["minLength"] = field.min_length
        if field.max_length is not None:
            js["maxLength"] = field.max_length
        if field.pattern:
            js["pattern"] = field.pattern
        if field.enum_values:
            js["enum"] = field.enum_values

        if field.type == SchemaType.DATE:
            js["format"] = "date"
        if field.type == SchemaType.DATETIME:
            js["format"] = "date-time"
        if field.type == SchemaType.GUID:
            js["format"] = "uuid"

        return js

    properties = {}
    required = []

    for name, field in schema.fields.items():
        properties[name] = field_to_json_schema(field)
        if field.required:
            required.append(name)

    return {
        "$schema": "http://json-schema.org/draft-07/schema#",
        "title": schema.name,
        "description": schema.description,
        "type": "object",
        "properties": properties,
        "required": required
    }

# Export to JSON Schema
json_schema = export_to_json_schema(COST_ESTIMATE_SCHEMA)
print(json.dumps(json_schema, indent=2))

Integration with DDC Pipeline

python
# Validate API request before processing
def validate_api_request(endpoint: str, payload: dict) -> SchemaValidationResult:
    schema_map = {
        '/api/estimates': 'CostEstimate',
        '/api/schedules': 'ProjectSchedule',
        '/api/rfis': 'RFI',
        '/api/bim/elements': 'BIMElement'
    }

    schema_name = schema_map.get(endpoint)
    if not schema_name:
        result = SchemaValidationResult(is_valid=True)
        return result

    registry = ConstructionSchemaRegistry()
    return registry.validate(payload, schema_name)

# Use in API handler
@app.post('/api/estimates')
def create_estimate(payload: dict):
    validation = validate_api_request('/api/estimates', payload)
    if not validation.is_valid:
        return {'error': 'Validation failed', 'details': [e.__dict__ for e in validation.errors]}, 400

    # Process valid data
    return process_estimate(payload)

Resources

• JSON Schema: https://json-schema.org/
• CSI MasterFormat: Standard classification codes
• IFC Schema: https://standards.buildingsmart.org/IFC/