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The Management of Spatial and Temporal Constraints in GIS using Pictorial Interaction on the Web

The Management of Spatial and Temporal Constraints in GIS using Pictorial Interaction on the Web. Fernando Ferri IRPPS-CNR-Italy Patrizia Grifoni IRPPS-CNR-Italy Maurizio Rafanelli IASI-CNR-Italy. The problem. To make available geographical databases by Web. The aim of the paper.

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The Management of Spatial and Temporal Constraints in GIS using Pictorial Interaction on the Web

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  1. The Management of Spatial and Temporal Constraints in GIS using Pictorial Interaction on the Web Fernando Ferri IRPPS-CNR-Italy Patrizia Grifoni IRPPS-CNR-Italy Maurizio Rafanelli IASI-CNR-Italy

  2. The problem To make available geographical databases by Web

  3. The aim of the paper XPQL (eXtended Pictorial Query Language) mapped in Geographic Markup Language (GML 3.0).

  4. The eXtended Pictorial Query Language The XPQL query language has: • a set of spatial operators • G-union, G-difference, G-disjunction, G-touching, G-inclusion, G-crossing, G-pass-through, G-overlapping, G-equality, G-distance, G-any and G-alias • a set of temporal operators: • T-before, T-meets, T-overlaps, T-starts, T-during, T-finishes and T-equals • symbolic geographical objects (sgo).

  5. Symbolic geographical objects sgo definition: <id, objclass, Σ, Λ > where: • id is the sgo identifier; • objclass is the set (possibly empty) of classes iconized by ψ ; • Σ represents the attributes to which the user can assign a set of values. Some attributes can be referred to a temporal dimension; • Λ is the ordered set of pairs (h, v), which defines the spatial characteristics and position of the sgo with respect to a reference point in the working area.

  6. Geometric characteristics of an sgo Let ybe an sgo, we have: ∂y = geometric border of y ; it is defined as: • ify is a polygon, ∂yis the set of its accumulation points (as defined in the set theory); • if yis an open polyline, ∂yis formed by its extreme points; • if yis a point ∂yis the empty set. • y°= y - ∂y = geometrical interior of y

  7. Geometric characteristics of an sgo • Dim(y) • 0 if ycontains at least one point but no polylines or polygons • 1 if ycontains at least one polyline but no polygons • 2 if ycontains at least one polygon.  

  8. The spatial operators of XPQL • G-union definition (Uni): The G-union of two sgo yi and yj is a new sgo defined as the set of all points belonging to yi e and/or yj. • G-touching definition (Tch): G-touching between two sgo yi and yj exists iff the points common to the two yare all contained in the union of their boundaries. If this condition is satisfied, the result of this operation between yi and yj is a new ψ called ψh and defined by the set of points common to yi and yj.

  9. The spatial operators of XPQL • G-inclusion definition (Inc): An sgo yi G-includes another sgo yj (and we write ψ i Inc ψ j) iff all the points of yj are also points of yi. The result is an sgo yh which coincides with the second operand yj. • G-disjunction definition (Dsj): Two sgo yi and yj are G-disjoined between them (formally ψ i Dsj ψ j) if the intersection of their borders AND the intersection of their internal points is null.

  10. The spatial operators of XPQL • G-pass-through definition (Pth): Let yi be a polyline and let yj be a polygon. Then, the operator G-pass-through is applicable iff the polyline is partially inside the polygon (formally ψ i Pth ψ j).

  11. The spatial operators of XPQL • G-distance definition (Dst): Let yi, yj ÎAbe two sgo of any type. Their distance is valuable and and ¡>=0 iff their intersection is null. The (minimum) distance Dst (f = min) between them is a numeric value that represents this distance. This operator can be used to find all sgo having distance θ (θ being one of the following symbols: >, <, =, , , ≠) from the reference sgo. The distance ( df ) value is given by: df (yi, yj)= yh where • yh indicates a bi-oriented segment representing the distance operator between y i , yj • fis the qualifier which solves this ambiguity • is a selection expression that includes conventional operators (>, <, =, ≠, etc.) or methods that behave like operators.

  12. The spatial operators of XPQL • G-difference definition (Dif): Let yi, yj ÎAbe two sgo. The difference between two symbolic objects y i and yj is defined as a new sgo (yh) which contains all the points which belong to yi but not to yj. • G-crossing definition (Crs): Let , yi ÎAbe two polylines, and let y°i y°j≠ Æ. Then, Cross: yi Crs yj := yh={x: x Î y°i y°j } and yh Î A. • G-overlapping Definition (Ovl): Let yi, yj ÎAbe two sgo of the same type. A non-null overlap exists between them iff their intersection is also non-null and has the same dimension as the sgo.

  13. The spatial operators of XPQL • G-equality definition (Eql): Two symbolic geographical objects yi and yj are topologically equal if they are of the same type and have the same shape. • G-any Definition (Any): Let ψi, ψj ∈ A be two sgo. Between them any admissible relationship is valid if the G-any operator is applied between them. • G-alias Definition (Als): Let yi be a sgo. yj is an alias of yiif the only difference between them is their shape.

  14. The temporal operators of XPQL • T-before (Bef) Definition: An attribute syih of the sgo yi is T-before another attribute syjk of the sgo yj ifsyih takes values (of the interval or instant) temporally “before” syjk (of the interval or instant). The attributes can take both intervals and instants as values. • T-meets (Mts) Definition: An attribute syih of the sgo yiT-meets another attribute syjk of the sgo yjif syih takes the maximum value (of the interval or instant)temporally “coincident” with the minimum value of syjk (of the interval or instant). The attributes can take both intervals and instants as values.

  15. The temporal operators of XPQL • T-overlap (TOv) Definition: An attribute syih of the sgo yiT-overlaps another attribute syjk of the sgo yj if syih takes the minimum value temporally “before” the minimum value of σψ jk and the maximum value temporally “after” the minimum value of syjk . Both attributes can take intervals as values. • T-starts (Sts) Definition: An attribute syih of the sgo yiT-starts another attribute syjk of the sgo yj if syih takes the minimum value (of the interval or instant) temporally“coincident” with the minimum value of syjk (of the interval or instant). The attributes can take both intervals and instant as values.

  16. The temporal operators of XPQL • T-during (Drg) Definition: An attribute syih of the sgo yi is defined as T-during another attribute syjk of the sgo yj if syih takes the minimum value temporally “after” the minimum value of σψ jk and the maximum value temporally “before” the maximum value of syjk . Both attributes can take intervals as values. • T-finishes (Fns) Definition: An attribute σψ iof the sgo T-finishes another attribute syjk of the sgo yj if syih takes the maximum value (of the attribute or instant) temporally “coincident” with the maximum value of syjk (of the interval or instant). The attributes can take both intervals and instants as values.

  17. The temporal operators of XPQL • T-equals (Tes) Definition: An attribute σψ ih of the sgo ψi T-equals another attribute syjk of the sgo yj if syih takes the minimum and maximum values (of the interval or instant) temporally “coincident” with the minimum and maximum values of syjk (of the interval or instant). The attributes can take both intervals and instants as values.

  18. Translating from XPQL to GML GML is used for coding the XPQL operands, operators. There are spatial and temporal operands

  19. Spatial feature XPQL features are: • Point, Polyline, Polygon. Their GML representation: • geometric classes PointType, LineStringType and PolygonType

  20. PointType Complex Type PointType <complexType name="PointType"> <complexContent> <extensionbase="gml:AbstractGeometricPrimitiveType"> <sequence> <choice> <element ref="gml:pos" /> <element ref="gml:coordinates" <element ref="gml:coord" </choice> </sequence> </extension> </complexContent> </complexType>

  21. LineStringType Complex Type LineStringType <complexType name="LineStringType"> <complexContent> <extension base="gml:AbstractCurveType"> <sequence> <choice> <choice minOccurs="2" maxOccurs="unbounded"> <element ref="gml:pos" /> <element ref="gml:pointRep" /> <element ref="gml:coord" /> </choice> <element ref="gml:coordinates" /> </choice> </sequence> </extension> </complexContent> </complexType>

  22. PolygonType Complex Type PolygonType Complex Type PolygonType <complexType name="PolygonType"> <complexContent> <extension base="gml:AbstractSurfaceType"> <sequence> <element ref="gml:exterior" minOccurs="0" /> <element ref="gml:interior" minOccurs="0" maxOccurs="unbounded" /> </sequence> </extension> </complexContent> </complexType>

  23. Temporal features XPQL features are: • Instant and interval. Their GML representation: • TimeInstant and TimePeriod

  24. TimeInstant <element name="TimeInstant" type="gml:TimeInstantType" substitutionGroup= "gml:_TimePrimitive"/> <complexType name="TimeInstantType" final="#all"> <complexContent> <extension base="gml:TimePrimitiveType"> <sequence> <element ref="gml:timePosition"/> </sequence> </extension> </complexContent> </complexType>

  25. TimePeriod <element name="TimePeriod" type="gml:TimePeriodType" substitutionGroup="gml:_TimePrimitive"/> <complexType name="TimePeriodType" final="#all"> <complexContent> <extension base="gml:TimePrimitiveType"> <sequence> <element ref="gml:begin"/> <element ref="gml:end"/> <element ref="gml:_duration" minOccurs="0"/> </sequence> </extension> </complexContent> </complexType> <element name="begin" type="gml:TimeInstantPropertyType"/> <element name="end" type="gml:TimeInstantPropertyType"/>

  26. Coding spatial and temporal operators • The XPQL temporal operators are derived from GML: AssociationType • For the XPQL spatial operators, FeaturePropertyType is a particular class of properties (using the gml:AssociationType pattern) which defines associations between features.

  27. AssociationType <complexType name="AssociationType"> <sequence> <element ref="gml:_Object" minOccurs="0"/> </sequence> <attributeGroup ref="gml:AssociationAttributeGroup"/> </complexType> <element name="_association" type="gml:AssociationType" abstract="true"/>

  28. FeaturePropertyType <complexType name="FeaturePropertyType"> <sequence> <element ref="gml:_Feature" minOccurs="0"/> </sequence> <attributeGroup ref="gml:AssociationAttributeGroup"/> </complexType>

  29. Query expressed by GML “Find all roads built between the years 1980 and 1990 that pass through provinces created after 1975”

  30. Query expressed by GML type definitions for operators =========================== --> ………… <complexType name="G-pass-throughType"> <complexContent> <extension base="gml:FeaturePropertyType"> <sequence> …………………….. </sequence> </extension > </complexContent> </complexType> ………… <complexType name="T-beforeType"> <complexContent> <extension base="gml:AssociationType"> <sequence> …………………….. </sequence> </extension > </complexContent> </complexType>

  31. Query expressed by GML <!-- ============================= type definitions for different geographical layers ================================--> ………… <complexType name="ProvinceType"> <complexContent> <extension base="gml:PolygonType"> <sequence> ………………….. </sequence> </extension> </complexContent> </complexType> ………… <complexType name="RoadType"> <complexContent> <extension base="gml:LineStringType"> <sequence> ………………………… </sequence> </extension> </complexContent> </complexType> …………

  32. Query expressed by GML <!-- ============================ the query example ============================= --> <QueryModel …………………> <gml:name>Example</gml:name> ………………….. <queryMember> <Province> ……………….. </Province> </queryMember> <queryMember> <Road> </Road> </queryMember> <queryMember> <G-pass-through> ……………….. </G-pass-through > </queryMember> <queryMember> <T-before> ……………….. </T-before> </queryMember> ……………….. </QueryModel>

  33. Conclusion We are now focusing our activities on designing and implementing a new pictorial language in areas different from the geographical one. Our hope is to be able to specify relational queries in this way, without the end user needing to understand the intricacies of boolean logic or set theory.

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