We compare structured and unstructured overlays and derive a hybrid overlay that can outperform both. Unstructured overlays build a random graph and use flooding or random walks on that graph to discover data stored by overlay nodes. Structured overlays assign keys to data items and build a graph that maps each key to the node that stores the corresponding data. Unstructured overlays are widely...

In this paper we present a systematic analysis of document retrieval using unstructured and structured queries within the score region algebra (SRA) structured retrieval framework. The behavior of different retrieval models, namely Boolean, tf.idf, GPX, language models, and Okapi, is tested using the transparent SRA framework in our three-level structured retrieval system called TIJAH. The retr...

Electronic health records capture patient information using structured controlled vocabularies and unstructured narrative text. While structured data typically encodes lab values, encounters and medication lists, unstructured data captures the physician's interpretation of the patient's condition, prognosis, and response to therapeutic intervention. In this paper, we demonstrate that informatio...

Chen (2001) coined the term ‘digital preservation paradox’ to describe a philosophy of preservation management that recognises change as a cornerstone of managing digital records for permanence. Paradox also surrounds use of the terms ‘structured’ and ‘unstructured’. As more and more so-called ‘unstructured’ information sources are generated from ‘structured’ repositories, preservation planning...

Minimal structured perturbations are constructed such that an approximate eigenpair of a nonlinear eigenvalue problem in homogeneous form is an exact eigenpair of an appropriately perturbed nonlinear matrix function. Structured and unstructured backward errors are compared. These results extend previous results for (structured) matrix polynomials to more general functions. Structured and unstru...