Web pages are becoming more complicated,both in appearance and in the underlying business models. Just as page composition for print media mix news, advertising, and regional content,web pages are increasingly the result of many hands. The Internet facilitates a delayed evaluatiom model for customization , and the composition process for pages is becoming a pipelined process,with each stage controlled by a different machine, in some cases under the auspices of different authorities, such as content delivery network operators. There is currently no formal model for defining data integrity in such an amorphous environment. An authorization and validation model can be constructed based on well-defined message parts and a simple composition language. The W3C XML signature standard serves as a base model for the definitions proposed in this paper.