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A Spatio-Temporal Query Language for a data model based on XML. J. E. Córcoles, J. García-Consuegra, J. Peralta and E. Navarro. Index. Introduction STQ Syntax Query Processing Query Decomposition Operator Execution Example of Query Processing Conclusions Future Work. Index. - PowerPoint PPT Presentation
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A Spatio-Temporal Query Language for a data model based
on XML.
J. E. Córcoles, J. García-Consuegra, J. Peralta and E. Navarro
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Index• Introduction
• STQ Syntax
• Query Processing» Query Decomposition
» Operator Execution
• Example of Query Processing
• Conclusions
• Future Work
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Index• Introduction
• STQ Syntax
• Query Processing» Query Decomposition
» Operator Execution
• Example of Query Processing
• Conclusions
• Future Work
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Introduction (I)
• XML (eXchanged Markup Language)
• XML => The solution to the problem of these heterogeneous systems
• XML => Exchange language of geographic information
• OpenGIS => GML (Geography Markup Language)
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Introduction (II)
• STQ (Spatio-Temporal Query language) over GML.
• Select-from-where syntax
• Spatial operators (overlap, cross, etc)
• Temporal operators (after, before, etc).
• Traditional operators (=,>, <,...) for non-spatial information
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Index• Introduction
• Syntax of STQ
• Query Processing» Query Decomposition
» Operator Execution
• Example of Query Processing
• Conclusions
• Future Work
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Syntax of STQ (I)
• Clean Semantics
• Path Expressions
• Ability to return an XML document
• Ability to query and return XML tags and attributes
• Intelligence type coercion
• Handles unexpected data
• Ability to allow queries when the DTD is not fully known
• Returns unnamed attributes
• Preserves Order
• Allows Spatial and Temporal operators
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Syntax of STQ (I)
1. Clean SemanticsSelect C.modelMember.Parcel.cadastreId
From [http://www.uclm.es//prove.xml].CityModel as C
Where C.name Like ‘Albacete’
2. Path ExpressionsC.modelMember.Parcel
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Syntax of STQ (II)
3. Ability to return an XML documentSelect C. ModelMemeber.Parcel.extendOf
From [http://www.uclm.es//prove.xml].CityModel as C
Where C.name Like ‘Albacete’ and Parcel.number = 103
The XML document return for the query is:<Polygon>
<outerBoundaryIs>
<LinearRing>
<coordinates>
0.0,0.0 40.0,0.0 40.0,10.0 0.0,10.0
</coordinates>
</LinearRing>
</outerBoundaryIs>
</Polygon>
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Syntax of STQ (III)
4. Ability to query and return XML tags and attributes
Select M.Parcel.extendOfFrom [http://www.uclm.es//probe.xml].CityMode.modelMember as MWhere M.(street%) Like ‘Capitan Grant’
5. Intelligence type coercion (String-Integer).
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Syntax of STQ (IV)
6. Handles unexpected data
7. Ability to allow queries when the DTD is not fully knownSelect C
From [http://www.uclm.es//prove.xml].CityModel as C
Where C.(name | description) Like ‘Albacete’
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Syntax of STQ (V)
8. Returns unnamed attributes
Select C.(^ modelDate, ^modelMember)From [http://www.uclm.es//prove.xml].CityModel as C
9. Preserves Order. » In the current version of STQ data order is not
preserved
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Syntax of STQ (VI)
10. Allows Spatial and Temporal operators
• Spatial Operators:»Disjoint, Meet, Equal, Overlap,
Contains, Inside), Covers and covered_by.
»Within, Near, Crossing, Along, Finish» Length, Surface, Perimeter and Buffering.
• Temporal Operators:» Date Is, After and Before
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Syntax of STQ (VII)
• Other features of STQ is the possibility to use several XML documents in the same query.
select_statement ::=.
.
FROM table_commalist: f1
table_commalist ::= addresshttp: d1 PERIOD table:s1 AS NAME:a1
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Index• Introduction
• Syntax of STQ
• Query Processing» Query Decomposition
» Operator Execution
• Example of Query Processing
• Conclusions
• Future Work
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Query Processing (I)
• The query process for a STQ query has two well-defined phases:» Query decomposition to transform the
STQ query into an Operator Tree.» To run the Algebra relational operators.
• Execution of alphanumeric operators (XQL)
• Execution of spatial operators (R-tree)
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Query Processing (II) Query Decomposition
• Query decomposition to transform the STQ query in an Operator Tree has four sub-phases:
• Normalization (conjunctive normal)
• Analysis (query graph or connection graph )
• Redundancy elimination • Rewriting (operator tree)
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Query Processing (III) Operator Execution
• After decomposition, a query may have two kinds of operators in the Select (Algebra relational) operator.» Alphanumeric operators (>,<,like): SQT is
based on XQL to execute alphanumeric operators
» Spatial operators STQ creates a R-tree spatial structure to execute spatial operators.
» Temporal operators: SQT is based on XQL to execute temporal operators of higher level.
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Index• Introduction
• Syntax of STQ
• Query Processing» Query Decomposition
» Operator Execution
• Example of Query Processing
• Conclusions
• Future Work
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Example of Query Processing (I)
• Example :
» To obtain all Parcel Identifiers (<modelMember><cadastreId>) that have a number (<modelMember><number>) greater than 100, and whose surface is contained in the zone with name ‘Carretas’.
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Example of Query Processing (II)
• The SQT query that represents the last query may be:
Select P.Cadastreid
From [http://www.uclm.es//prove.xml].CityModel.modelMember.Parcel as P,
[http://www.uclm.es//prove.xml].CityModel.modelMember.District as D
Where P.number > 100 and D.name like ‘Carretas’ and
P.extendOf.Contain.(D.extendOf)
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Example of Query Processing (III)
• After the decomposition process, this query generates the following operator tree shown below.
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Example of Query Processing (IV)
• The result set is a XML document with the totality of elements that have carried out all the conditions. For example:
<cadastreId>
3050
</cadastreId>
<cadastreId>
3008
</cadastreId>
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Index• Introduction
• Syntax of STQ
• Query Processing» Query Decomposition
» Operator Execution
• Example of Query Processing
• Conclusions
• Future Work
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Conclusions
• STQ: Spatial and temporal query language over XML.
• Spatio-Temporal feature is not included in the most widely-known XML query languages
• STQ is applied over a GML data model.
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Index• Introduction
• Syntax of STQ
• Query Processing» Query Decomposition
» Operator Execution
• Example of Query Processing
• Conclusions
• Future Work
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Future Work
• Features such as Preserver order and Intelligence type coercion will be included
• Implementation of Dataguides:» Single user interface. » queries on the Web.
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• Questions and comments can be sent to the following e-mail address:
