The present invention provides a solution that unifies independent data sources into a single data source by hiding one of the data sources in metadata. The non-hidden source, which can reference the hidden source, can be processed by a primary XML processing agent. This agent can initially ignore syntax and semantics of content associated with the hidden source, which is contained within the metadata. A secondary XML processing agent can transform the hidden source into a readable form, which is consumable by the primary processing agent. The primary XML processing agent can receive this readable form as a content stream. The primary XML processing agent can be unaware that the content stream originates from the unified source, which permits the unified source to represent multiple sources while preserving “rules” that typically prohibit multiple data types to be included in a single source.