ROUTING XML QUERIES

• US 20100100552A1
• Filed: 12/22/2009
• Published: 04/22/2010
• Est. Priority Date: 04/22/2003
• Status: Active Grant

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Srivastava, Divesh, Koudas, Nikolaos, Rabinovich, Michael
• Granted Patent: US 8,001,146 B2
• Time in Patent Office: Days
• US Class Current: 707/742
• CPC Class Codes: G06F 16/2471 Distributed queries
• CPC Class Codes: G06F 16/835 Query processing

Abstract

A vast amount of information currently accessible over the Web, and in corporate networks, is stored in a variety of databases, and is being exported as XML data. However, querying this totality of information in a declarative and timely fashion is problematic because this set of databases is dynamic, and a common schema is difficult to maintain. The present invention provides a solution to the problem of issuing declarative, ad hoc XPath queries against such a dynamic collection of XML databases, and receiving timely answers. There is proposed a decentralized architectures, under the open and the agreement cooperation models between a set of sites, for processing queries and updates to XML data. Each site consists of XML data nodes. (which export their data as XML, and also pose queries) and one XML router node (which manages the query and update interactions between sites). The architectures differ in the degree of knowledge individual router nodes have about data nodes containing specific XML data. There is therefore provided a method for accessing data over a wide area network comprising: providing a decentralized architecture comprising a plurality of data nodes each having a database, a query processor and a path index, and a plurality of router nodes each having a routing state, maintaining a routing state in each of the router nodes, broadcasting routing state updates from each of the databases to the router nodes, routing path queries to each of the databases by accessing the routing state.

Claims

1. A method for accessing data over a wide area network comprising:

providing a decentralized architecture comprising a plurality of data nodes and a plurality of routers, the data nodes having databases, routing information, query processors, and a path indexes, the routers having routing states;

restricting communication between the plurality of routers in accordance with an agreement;

initiating communication between at least two of the plurality of routers in accordance with the agreement, wherein initiating communication comprises sending an advertisement comprising at least one of a path insertion or path deletion by a first one of the plurality of routers to at least one of the plurality of routers with which the first one of the plurality of routers has the agreement; and

blocking propagation of the advertisement by the at least one of the plurality of routers with which the first one of the plurality of routers has the agreement when the at least one of the plurality of routers has more than one next-hop router in a routing state for path information associated with the advertisement.

2. The method of claim 1, further comprising:

restricting communication between the plurality of routers to a spanning tree protocol.

3. The method of claim 2, wherein the spanning tree protocol includes a plurality of spanning trees.

4. The method of claim 3, further comprising:

computing a number of spanning trees to be implemented; and

hashing a data path to at least one of the plurality of spanning trees included in the spanning tree protocol.

5. The method of claim 4, further comprising:

processing a plurality of data paths using different ones of the multiple spanning trees, each of the multiple spanning trees having a different one of the plurality of routers as a root.

6. The method of claim 5, further comprising:

computing at least one of a union and intersection of sets corresponding to neighboring ones of the plurality of routers.

7. The method of claim 1, further comprising:

sending a query from a first one of the plurality of routers to a second one of the plurality of the routers in accordance with the agreement; and

8. The method of claim 7, further comprising:

sending the query from the second one of the plurality of routers to a third one of the plurality of routers in accordance with the agreement, the first one of the plurality of routers and the third one of the plurality router not having the agreement so that direct communication between the first one of the plurality of routers and the third one of the plurality of routers is prohibited.

9. A system comprising:

a network having a decentralized architecture, the network comprising;

a plurality of data nodes each having a database, routing information, a query processor, and a path index; and

a plurality of router nodes each having a routing state, communication between the plurality of router nodes being restricted in accordance with an agreement, said routing nodes configured to;

broadcast routing information updates to said routing state from said databases to said router nodes;

create mapping indices to data items utilizing said routing state;

route path queries to said databases by following said mapping indices, said routing performed by initiating communication between at least two of the plurality of routers in accordance with the agreement, wherein initiating communication comprises sending an advertisement representing at least one of a path insertion or path deletion from a first one of the plurality of routers to at least one of the plurality of routers with which the first one of the plurality of routers has the agreement; and

block propagation of the advertisement by the at least one of those of the plurality of routers with which the first one of the plurality of routers has the agreement when the at least one of the plurality of routers has more than one next-hop router in a routing state for path information associated with the advertisement.

10. The system of claim 9, wherein communication between the plurality of routers is restricted to a spanning tree protocol.

11. The system of claim 10, wherein the spanning tree protocol includes a plurality of spanning trees.

12. The system of claim 11, wherein a number of spanning trees to be implemented is computed and a data path is hashed to at least one of the plurality of spanning trees included in the spanning tree protocol.

13. The system of claim 12, wherein a plurality of data paths are processed using different ones of the plurality of spanning trees, each of the plurality of spanning trees having a different one of the plurality of routers as a root.

14. The system of claim 13, wherein at least one of a union and intersection of sets corresponding to neighboring ones of the plurality of routers is computed.

15. The system of claim 9, wherein initiating communication comprises sending a query from a first one of the plurality of routers to a second one of the plurality of the routers in accordance with the agreement.

16. The system of claim 15, wherein information access is managed in the network by sending the query from the second one of the plurality of routers to a third one of the plurality of routers in accordance with the agreement, the first one of the plurality of routers and the third one of the plurality router not having the agreement so that direct communication between the first one of the plurality of routers and the third one of the plurality of routers is prohibited.

17. The system of claim 16, wherein information access is managed in a network by sending the advertisement from the at least one of the plurality of routers with which the first one of the plurality of routers has the agreement to another router that does not have the agreement with the first one of the plurality of routers.