The IBM Journal of Research and Development is a peer-reviewed technical journal, published bimonthly, which features the work of authors in the science, technology and engineering of information systems. Papers are written for the worldwide scientific research and development community and knowledgeable professionals. Submitted papers are welcome from the IBM technical community and from non-IBM authors on topics relevant to the scientific and technical content of the Journal. In addition to papers, the Journal contains complete reference lists of patents issued to IBM inventors and papers published by IBM authors in other journals. The last issue each year contains a subject and author index for that year.