An important aspect of document understanding is document logical structure derivation, which involves knowledge-based analysis of document images to derive a symbolic description of their structure and contents. Domain-specific as well as generic knowledge about document layout is used in order to classify, logically group, and determine the read-order of the individual blocks in the image, i.e., translate the physical structure of the document into a layout-independent logical structure. We have developed a computational model for the derivation of the logical structure of documents. Our model uses a rule-based control structure, as well as a hierarchical multi-level knowledge representation scheme in which knowledge about various types of documents is encoded into a document knowledge base and is used by reasoning processes to make inferences about the document. An important issue addressed in our research is the kind of domain knowledge that is required for such analysis. A document logical structure derivation system (DeLoS) has been developed based on the above model, and has achieved good results in deriving the logical structure of complex multi- articled documents such as newspaper pages. Applications of this approach include its use in information retrieval from digital libraries, as well as in comprehensive document understanding systems.