Lumen Technologies Lumen Technologies Qwilt This document specifies a set of objects extending the Content Delivery Network Interconnection (CDNI) metadata model to allow for metadata to be applied conditionally and at various points in a dCDNs processing of requests. The concept of Processing Stages are introduced, where each stage in a CDN's processing pipeline presents an opportunity to examine requests and responses and make alterations as needed. Metadata, such as caching rules, can be applied conditionally (based on aspects of an HTTP request header), and HTTP responses from a source can be altered dynamically (such as adding or dropping an HTTP header). This standard leverages the expression language documented in the Metadata Expression Language (MEL) Specification.