Michael Benedikt

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We study structural properties of each of the main<lb>sublanguages of XPath [8] commonly used in practice.<lb>First, we characterize the expressive power of these lan-<lb>guage fragments in terms of both logics and tree pat-<lb>terns. Second, we investigate closure properties, fo-<lb>cusing on the ability to perform basic Boolean oper-<lb>ations while(More)
The emerging paradigm of electronic services promises to bring to distributed computation and services the flexibility that the web has brought to the sharing of documents. An understanding of fundamental properties of e-service composition is required in order to take full advantage of the paradigm. This paper examines proposals and standards for(More)
The expressive power of first-order query languages with several classes of equality and inequality constraints is studied in this paper. We settle the conjecture that recursive queries such as parity test and transitive closure cannot be expressed in the relational calculus augmented with polynomial inequality constraints over the reals. Furthermore,(More)
The popularity of collaborative tagging sites presents a unique opportunity to explore keyword search in a context where query results are determined by the opinion of a network of taggers related to a seeker. In this paper, we present the first in-depth study of network-aware search. We investigate efficient top-k processing when the score of an answer is(More)
This paper aims to provide a better formalism for describing properties of linked data structures (e.g., lists, trees, graphs), as well as the intermediate states that arise when such structures are destructively updated. The paper deenes a new logic that is suitable for these purposes (called Lr, for \logic of reachability expressions"). We show that Lr is(More)
A form-based service is one in which the ow of data between service and user is described by a sequence of query/response interactions, or forms. A form provides a user interface that presents service data to the user, collects information from a user and returns it to the service. Mawl is a domain-speci c language for programming form-based services in a(More)
An ever-growing number of users participate in online communities such as Flickr, del.icio.us , and YouTube , making friends and sharing content. Users come to these sites to find out about general trends – the most popular tags, or the most recently tagged item – as well as for more specific information, such as the recent posts of one of their friends.(More)