6149937
Publishing Relational Data in XML: the SilkRoute Approach
Xyleme is a dynamic warehouse for XML data of the Web supporting query evaluation, change control and data integration. We briefly present our motivations, the general architecture and some aspects of Xyleme. The project we describe here was completed at the end of 2000. A prototype has been implemented. This prototype is now being turned into a product by a start-up company also called Xyleme [14]. Xyleme: a complex tissue of wood cells, functions in conduction and storage ...
1399759
Warehousing and incremental evaluation for Web Site management
Recently, several systems have been proposed for building Web sites from declarative spec-iications. The salient feature of these systems is that they model both the structure and the content of a Web site as a view over some existing raw data. In this \Web site as view" paradigm, a critical issue is when to compute the site. One approach is to materialize the site completely before the users browse it: the disadvantages of this approach are high maintenance costs and stale data. Moreover, this approach is not applicable if the Web site has forms, because then the queries deening the Web site depends on user input. The other extreme approach is to precompute only the root(s) of the Web site, and then compute dynamically (at \click time") the queries that retrieves the information required to display the next page. In this paper we address the problem of choosing the optimal connguration for run-time management of a declaratively speciied Web site, trading oo the beneets of precomputation and incremental evaluation. First, we identify several novel optimizations that need to be considered in addition to optimizations obtained by precomputing views. These optimizations include simplifying queries based on contexts that can be derived from the browsing patterns, and lookahead computation. Second, we describe an algorithm for cost based search of a space of conngurations which include the above optimizations. Finally, given a connguration we show how to reformulate our Web-site deenition to exploit the views and data being cached.
14181773
Nominal rewriting
Nominal rewriting is based on the observation that if we add support for @a-equivalence to first-order syntax using the nominal-set approach, then systems with binding, including higher-order reduction schemes such as @l-calculus beta-reduction, can be smoothly represented. Nominal rewriting maintains a strict distinction between variables of the object-language (atoms) and of the meta-language (variables or unknowns). Atoms may be bound by a special abstraction operation, but variables cannot be bound, giving the framework a pronounced first-order character, since substitution of terms for variables is not capture-avoiding. We show how good properties of first-order rewriting survive the extension, by giving an efficient rewriting algorithm, a critical pair lemma, and a confluence theorem for orthogonal systems.
16649053
Coinductive techniques for operational equivalence of interaction nets
In this paper we study a notion of operational equivalence for interaction nets, following the recent success of applying methods based on bisimulation to functional and object oriented programming languages. We set up notions of contextual equivalence and bisimilarity and show that they coincide. A coinduction principle then gives a simple and robust way of showing when two interaction nets are contextually equivalent. We include several examples to demonstrate the usefulness of the approach, in particular for optimizing interaction nets.
3029296
Strong Normalization of Typeable Rewrite Systems
This paper studies termination properties of rewrite systems that are typeable using intersection types. It introduces a notion of partial type assignment on Curryfied Term Rewrite Systems, that consists of assigning intersection types to function symbols, and specifying the way in which types can be assigned to nodes and edges between nodes in the tree representation of terms. Using a more liberal approach to recursion, a general scheme for recursive definitions is presented, that generalizes primitive recursion, but has full Turing-machine computational power. It will be proved that, for all systems that satisfy this scheme, every typeable term is strongly normalizable.
12283254
Iterator Types
System L is a linear λ-calculus with numbers and an iterator, which, although imposing linearity restrictions on terms, has all the computational power of Godel's System τ. System L owes its power to two features: the use of a closed reduction strategy (which permits the construction of an iterator on an open function, but only iterates the function after it becomes closed), and the use of a liberal typing rule for iterators based on iterative types. In this paper, we study these new types, and show how they relate to intersection types. We also give a sound and complete type reconstruction algorithm for System L.
1019046
Implementing Nominal Unification
Nominal matching and unification underly the dynamics of nominal rewriting. Urban, Pitts and Gabbay gave a nominal unification algorithm which finds the most general solution to a nominal matching or unification problem, if one exists. Later the algorithm was extended by Fernandez and Gabbay to deal with name generation and locality. In this paper we describe first a direct implementation of the nominal unification algorithm, including the extensions, in Maude. This implementation is not efficient (it is exponential in time), but we will show that we can obtain a feasible implementation by using termgraphs.