A Deterministic Model for Semistructured and Structured Data

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With the development of the Internet, databases are being copied, transformed, and corrected on an unprecedented scale. With this comes the need to annotate data: for correcting it, commenting on it, or for recording its provenance. However, conventional databases have a regular structure and provide no "room" for annotations which are typically irregular and required at all levels of granularity. Annotations require some form of semistructured representation. This investigation centers on a new model for structured and semistructured data which is intended to facilitate the process of data annotation. The usual models of semistructured data are based on an edge-labeled graph and are "nondeterministic" in that a given vertex may have several out-edges with the same label. The model proposed here is more restrictive in that these labels must all be different. It is less restrictive because the labels themselves may themselves carry data. In fact a label may itself be a small piece of semistructured data. A number of advantages are claimed for this model. Like XML, the data representation is entirely syntactic. All operations are syntactic,, and serialization of data is immediate. Object identifiers in particular are syntactic constructs, they have structure, and certain database transformations may be achieved by manipulation of this structure. The goal of the investigation is to develop the model and associated interfaces so that it can be used as a common representation for both semistructured and structured data. A second goal is to develop tools for data annotation. http://db.cis.upenn.edu/Research/