Schema Evolution

Technical Definition

Schema Evolution refers to the systematic approach of maintaining scrapers when target websites modify their HTML structure, API contracts, or data formats. Sites regularly change class names, restructure DOM hierarchies, rename API endpoints, modify JSON schemas, or completely redesign pages. Robust scraping operations implement version detection, selector abstraction, automated change detection, and graceful degradation when schemas drift. The goal is minimizing downtime and manual intervention when evolution occurs.

Business Use Case

Enterprise data providers maintain hundreds of scrapers, each vulnerable to site changes. When an e-commerce platform redesigns product pages, schema evolution protocols detect broken selectors, alert operations teams, and potentially activate fallback extraction strategies. Financial data services track regulatory filing format changes, adapting parsers when SEC or other authorities modify their XML schemas or HTML templates.

Pro-Tip

Implement selector version pinning with automated change detection. Version your selectors, track extraction success rates per version, and automatically flag when success drops below thresholds. Maintain fallback selector chains ordered by specificity—primary selectors, backup selectors, and emergency regex patterns. Use visual regression testing on screenshots to detect structural changes even when data extraction technically succeeds.