Abstract: A system and method for developing an application for serving a document to a client in a client/server network employs an Object Model which defines templates, extensions, documents, and content objects in a template inheritance model. The Object Model serves a document, such as a webpage of a Web site application, by combining the structure and content inherited from a template and extensions in the template hierarchy. The templates specify the structure of the document and include tags as placeholders for content objects to be incorporated in the document. Extensions descend from either a template or another extension, and can expand upon the number of tags specified in a parent, add additional formatting to the layout, and/or refine the definition of tags that already exist in the inheritance hierarchy. When a document is to be viewed or served, a page server retrieves the template hierarchy and incorporates all tagged content in the structure inherited from the template and its extensions.