Difference between revisions of "Data Sources"
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The information hosted in a gCube infrastructure is partitioned among different Data Sources. All Data Sources build on a common interface, that is defined by the [http://www.loc.gov/standards/sru/specs/cql.html Contextual Query Language(CQL)]. For example consider the CQL query Q : '((title any "marine polution") AND (type = "report")) NOT (location within "Europe")'. The results of this query are the report documents that have a title which contains any if the words "marine" and "polution", and define a location outside Europe. | The information hosted in a gCube infrastructure is partitioned among different Data Sources. All Data Sources build on a common interface, that is defined by the [http://www.loc.gov/standards/sru/specs/cql.html Contextual Query Language(CQL)]. For example consider the CQL query Q : '((title any "marine polution") AND (type = "report")) NOT (location within "Europe")'. The results of this query are the report documents that have a title which contains any if the words "marine" and "polution", and define a location outside Europe. | ||
| − | Each Data Source implements only a subset of all the CQL standards defined in the [http://www.loc.gov/standards/sru/ | + | Each Data Source implements only a subset of all the CQL standards defined in the [http://www.loc.gov/standards/sru/resources/cql-context-set-v1-2.html CQL Context Set 1.2]. Depending on the underlying technologies used in each case, an efficient implementation of various CQL standards is impracticable for some Data Sources. Consequently, different Data Sources support different CQL standards. |
During the Planning process, it is necessary to detect which of the Data Sources must be involved and provide their contribution to the final outcome of the query. The Query Planner of the Search System needs to take into consideration the CQL capabilities of each Source and the information they host. The search space explored by the Planner comprises all the, equivalent to the initial, queries and the corresponding alternative plans. These alternatives may involve different sets of Data Sources, but still generate the same final outcome for the initial query. In Section ZZZ we will give an outline of the two-stage Planning process implemented in the gCube Search System. | During the Planning process, it is necessary to detect which of the Data Sources must be involved and provide their contribution to the final outcome of the query. The Query Planner of the Search System needs to take into consideration the CQL capabilities of each Source and the information they host. The search space explored by the Planner comprises all the, equivalent to the initial, queries and the corresponding alternative plans. These alternatives may involve different sets of Data Sources, but still generate the same final outcome for the initial query. In Section ZZZ we will give an outline of the two-stage Planning process implemented in the gCube Search System. | ||
Revision as of 15:29, 22 July 2011
CQL-enabled Data Sources
The information hosted in a gCube infrastructure is partitioned among different Data Sources. All Data Sources build on a common interface, that is defined by the Contextual Query Language(CQL). For example consider the CQL query Q : '((title any "marine polution") AND (type = "report")) NOT (location within "Europe")'. The results of this query are the report documents that have a title which contains any if the words "marine" and "polution", and define a location outside Europe. Each Data Source implements only a subset of all the CQL standards defined in the CQL Context Set 1.2. Depending on the underlying technologies used in each case, an efficient implementation of various CQL standards is impracticable for some Data Sources. Consequently, different Data Sources support different CQL standards. During the Planning process, it is necessary to detect which of the Data Sources must be involved and provide their contribution to the final outcome of the query. The Query Planner of the Search System needs to take into consideration the CQL capabilities of each Source and the information they host. The search space explored by the Planner comprises all the, equivalent to the initial, queries and the corresponding alternative plans. These alternatives may involve different sets of Data Sources, but still generate the same final outcome for the initial query. In Section ZZZ we will give an outline of the two-stage Planning process implemented in the gCube Search System.
