Abstract: A framework defining a family of index structures useful in evaluating XML path expressions (i.e., twigs) in XML database is disclosed. Within this framework, two particular index structures with different space-time tradeoffs are presented that prove effective for the evaluation of twigs with value conditions. These index structures can be realized using access methods of an underlying relational database system. Experimental results show that the indices disclosed achieve significant improvement in performance for evaluating twig queries as compared with previously proposed XML path indices.

Abstract: A method for publishing relational data as XML by translating XML queries into queries against an relational database. Conversion of the relational database into an XML database is not required. Each relational table is mapped to a virtual XML document, and XML queries are issued over these virtual documents. An XML query is parsed and transformed into a language-neutral intermediate representation, which is a sequence of operations describing how the output document is derived from the underlying relational tables. The intermediate representation is then translated into an SQL query over the underlying relational tables and into instructions for a tagger. The SQL query is executed, and the SQL query results are then fed into the tagger, which follows tagger instructions to generate the marked up output.

Abstract: A method for publishing relational data as XML by translating XML queries into queries against a relational database. Conversion of the relational database into an XML database is not required. Each relational table is mapped to a virtual XML document, and XML queries are issued over these virtual documents. An XML query is parsed and transformed into a language-neutral intermediate representation, which is a sequence of operations describing how the output document is derived from the underlying relational tables. The intermediate representation is then translated into an SQL query over the underlying relational tables. The intermediate representation is also used to generate a tagger graph, which the tagger runtime ‘walks’ to generate the tagged, structured XML output. Each of the nodes of the tagger graph are operators which perform processing on the results of the SQL query. The SQL query is executed, and the SQL query results are then provided to the tagger.

Abstract: A system, method, and computer program product for processing XML queries over relational data and meta-data using a relational database system. The invention runs a query to generate a view definition, so a regular query processor can handle queries on a mix of data and meta-data. Names of desired tables are data-dependent, so the invention represents a default XML view as an XML query over the relational tables, gets the table names and table data by recursively invoking the query processor (first by querying the catalog table, and then querying base data according to a new construct). The invention thus processes queries over table names in addition to table values.

Abstract: A method for storing XML documents in a relational database system while exploiting XML Schema information to capture information about types, inheritance, equivalence classes, and integrity constraints in the generated relational schema, enabling efficient querying. The invention simplifies complex XML schema types, translates the simplified XML schema types into relational tables, and then stores relations corresponding to each XML element in relational table rows. The simplification includes grouping all occurrences of a given element together, assembling two or more element types into element groups if the schema indicates that elements of those element types will occur the same number of times, and applying a number of transformation rules to the element groups. The translation includes constructing a type graph from the simplified schema, building an element graph for each global element in the simplified schema from the type graph, and generating relational tables from the element graph.

Abstract: A query optimization technique that determines whether any column from a right quantifier of a left outer join query is projected out of the query. If not, then all predicates in an ON clause are removed from the left outer join query, the right quantifier is removed from the left outer join query, and the left outer join query is converted to a simple select query. A number of steps are performed to determine whether any of the columns quantified by the right quantifier participate in a projection list of the query. A set of equivalence class columns is computed for the query, wherein the equivalence classes are derived from equi-join predicates in the query. A set of columns quantified by the right quantifier across the computed set of equivalence classes is computed. A determination is made whether a subset of the set of columns form a key for the right quantifier. If the right quantifier columns are not projected out of the query, then the optimization may be performed.

Abstract: A technique enabling querying of XML documents in a relational database system via a reconstruction view allowing XML documents to be queried as though XML views of relational data. A single query processor can be used with all relational schema generation methods (whether or not using XML schema information) to seamlessly query across XML documents, relational data, and XML views of relational data; no special purpose query processor is required. The technique creates an XML document view, creates relational tables for storing XML documents using relational schema, shreds the XML documents and stores the XML documents as rows in the relational tables according to the relational schema, generates a reconstruction view over the relational tables to define how the shredded documents are to be virtually reconstructed, and processes queries over the stored XML documents as queries over the reconstruction view.

Abstract: Apparatus and method for use in querying a database containing data records. The database is characterized by a compression scheme to provide data clustering information. In accordance with a exemplary embodiment of the invention a functional representation of data clustering is a Gaussian and the queries are performing by integrating the Gaussian corresponding to each of the data clusters over the ranges to determine the sum or the count of data records from the database that fall within the selected ranges. The process chooses a value for the cluster number K. The cluster model is next broken up into areas (tiles) based on user defined parameters. Data from the database is then classified based on the tiling information. A sorted version of the classified data, ordered by cluster number and then by the tile number within the cluster is generated. This data is then evaluated to test the sufficiency of the model created during the clustering.

Abstract: An apparatus and method for efficiently compressing contents of a database system to support ad hoc querying and OLAP type aggregation queries. This invention consists of a new compressed representation of the data cube that (a) drastically reduces storage requirements, (b) does not require the discretization hierarchy along each query dimension to be fixed beforehand and (c) treats each dimension as a potential target measure and supports multiple aggregation functions without additional storage costs. The tradeoff is approximate, yet relatively accurate, answers to queries. We outline mechanisms to reduce the error in the approximation. Our performance evaluation indicates that our compression technique effectively addresses the limitation of existing approaches. The basic method relies on representing the contents of the database by a probability distribution consisting of a mixture of Gaussians.

Abstract: A query optimization technique that determines whether any column from a right quantifier of a left outer join query is projected out of the query. If not, then all predicates in an ON clause are removed from the left outer join query, the right quantifier is removed from the left outer join query, and the left outer join query is converted to a simple select query. A number of steps are performed to determine whether any of the columns quantified by the right quantifier participate in a projection list of the query. A set of equivalence class columns is computed for the query, wherein the equivalence classes are derived from equi-join predicates in the query. A set of columns quantified by the right quantifier across the computed set of equivalence classes is computed. A determination is made whether a subset of the set of columns form a key for the right quantifier. If the right quantifier columns are not projected out of the query, then the optimization may be performed.

Abstract: A query optimization technique that determines whether a query includes a self join that is transitively derived through table expressions having UNION operators. If so, the query is simplified to eliminate the table expressions and to reduce the query to an equivalent query over tables.

Abstract: A method for publishing relational data as XML by translating XML queries into queries against a relational database. Conversion of the relational database into an XML database is not required. Each relational table is mapped to a virtual XML document, and XML queries are issued over these virtual documents. An XML query is parsed and transformed into a language-neutral intermediate representation, which is a sequence of operations describing how the output document is derived from the underlying relational tables. The intermediate representation is then translated into an SQL query over the underlying relational tables. The intermediate representation is also used to generate a tagger graph, which the tagger runtime ‘walks’ to generate the tagged, structured XML output. Each of the nodes of the tagger graph are operators which perform processing on the results of the SQL query. The SQL query is executed, and the SQL query results are then provided to the tagger.