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Thread:
Issue: How would a GML-based TransXML integrate with existing external schemas? |
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Paul Scarponcini
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Issue: How would a GML-based TransXML integrate with existing external schemas?
Posted:
Saturday, January 29, 2005 4:00 PM (EST)
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(I have separated out what are emerging as key issues regarding GML into separate threads to encourage focused discussion on these topics.)
The GML Experiment demonstrated, from a technical standpoint, that it is possible to integrate with existing external XML schemas by importing the external schema and then incorporating the parts of that schema (elements, attributes, types) that are appropriate. There are style and basic type differences that must be considered. From a practical standpoint, how and when this would be done depends on the individual TransXML and external schemas.
In the case of the TransXML Geometry Roadway Design (GRD) schema, LandXML has been identified as an existing, already robust and widely used XML schema. A GML version of LandXML has already been created, with translators available to convert instance documents between LandXML and LandGML. The focus of attention will therefore be on modeling GRD requirements with UML, seeing where LandXML may be deficient in these requirements, and then making recommendations to LandXML.org on possible enhancements to LandXML/LandGML.
In the case of TransXML Contract Pay Items, Bid Package, and Construction Quantities and Materials schemas, aecXML has been identified as an existing XML schema. It is not very extensive, has minimal current usage, and is looking towards TransXML to extend its scope. aecXML has some dependency on the IFC schema and NIBS has just signed a Memorandum of Understanding with OGC for collaboration on IFC and GML. It is therefore proposed that, if GML is adopted as the TransXML Framework, that we create an alternative, GML version of aecXML to replace the existing one instead of trying to link to what is there.
In the case of TransXML Crash Records, JusticeXML has been identified as a related, existing XML schema. It is lacking in crash specific content and they have expressed interest in working with us to develop this. Their approach to XML is an object-oriented one like GML, resulting in modularity of components. It is therefore proposed that, if GML is adopted as the TransXML Framework, we develop a GML version of Crash Records but try to utilize existing JusticeXML ancillary content where appropriate, for example, citations.
In the case of TransXML Highway Information Safety Analysis, several standards have been identified. The ISO 19133 Linear Referencing Standard defines a generalized method for specifying linear locations of crashes that can be used to link to roadway characteristics databases. GML implementations of it are already underway outside of this project so we should be able to help insure this happens. Two possible standards have been identified for representing the roadway characteristics themselves. The ISO ITS GDF standard is used by in-car navigation system base map data suppliers. A UML model and XML and GML encodings are nearing completion by the standards committee. The FGDC Framework Data Content Standard (AKA Geospatial One-Stop) will be mandated for State usage for exchanging GIS data. It contains a UML model and a GML encoding and is being readied for ANSI standards submittal.
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