Browse Prior Art Database

A Method and System to Answer the DESCRIBE Query for Linked Data Browsing of Relational Data

IP.com Disclosure Number: IPCOM000188589D
Original Publication Date: 2009-Oct-15
Included in the Prior Art Database: 2009-Oct-15

Publishing Venue

IBM

Abstract

In this disclosure, we propose a novel approach to answer the DESCRIBE query for Linked Data Browsing of relational data. The principle for our approach is that the generated SQL query should be highly efficient, and the SQL query results will transformed to the RDF triple list with complex computation in memory, rather than the generated SQL query will provide results that easily be transformed to RDF triple list at the cost of SQL query efficiency as in the prior arts. The efficient SQL is generated by reducing the sub-queries for both horizontal tables and vertical tables and developing an optimization framework and strategy to generate SQL queries.

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A Method and System to Answer the DESCRIBE Query for Linked Data Browsing of Relational Data

IBM Confidential June. 2008

Background:

Linked Data is about employing the Resource Description Framework (RDF) and the Hypertext Transfer Protocol (HTTP) to publish structured data on the Web and to connect data between different data sources, effectively allowing data in one data source to be linked to data in another data source. The principles of Linked Data were first outlined by Berners-Lee in 2006 [1], and provide broad guidance upon which data publishers have begun to realize the Web of Data. This guidance has been extended by technical documents such as [2][3] that capture best practices emerging from the Linked Data communityand provide recipes on which publishing systems can be based.

The Web of Data can be accessed using Linked Data browsers,

                                                                                  However, instead of following links between HTML pages, Linked Data browsers enable users to navigate between different data sourcesby following RDF links. This allows the user to start with one data source and then move through a potentially endless Web of data sources connected by RDF links. Just asthe traditional document Web can be crawled by following hypertext links, the Web of Data can be crawled by following RDF links. Working on the crawled data, search engines can provide sophisticated query capabilities, similar to those provided by conventional relational databases.

As present, most of structured data are stored in arelational database, it is recommended to leave the data there and just publish a Linked Data view onyour existing database
[2]. The tables in relational database can be classified as horizontal table and vertical table according to the storage of properties. The most common table is horizon table, in which the property is the column name and the object values are in the rows of the columns. However, if the real world object has many properties and only a small percentage of the property will be valued for one specific object, a commonly used storage pattern in relational database is vertical table, i.e. stored all the property in one column and with another column to indicate the property values. The three columns of vertical table is called subject column, predicate column and object column respectively. For example,

ID name age

6240001 John 23

6240002 Tom 56

just as the traditional Web of documents is accessed using HTML browsers.

Subject Predicate Object

6240001 name John

6240001 age 23

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6240002 name Tom

6240002 age 56

Figure 1. The left-side is an example of horizontal table and the right-side is a vertical table A commonly used tool for serving Linked Data views on relational databases is D2R Server [4], as shown in Figure 2. D2R server relies on the declarative D2RQ mapping [7] between the schemata of the database and the tar...