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37 Two UML modeling tools were utilized within the develop- It also provided verification of the structure and content of ment team: (1) IBM's Rational Rose (an "industrial strength" GML constructs. tool) and (2) Sparx Systems Enterprise Architect (a lower-cost In order to guide development of future TransXML schema, UML modeling tool). Appropriately, an XML-based modeling a template UML model and a companion template.xsd file data exchange format (XMI) was used to transfer model were developed. information across the two tools. Standard conventions for the TransXML UML models Future TransXML Schema Validation were established and documented for use by the data model- ers from the four business areas. A presentation was devel- For the purposes of future development of XML schemas oped on how to read UML class diagrams, and posted to the under the TransXML umbrella, the following requirements TransXML website as a resource for stakeholders wishing to are recommended: comment on the diagrams. UML models for the selected TransXML schemas are doc- 1. The schema should conform to the rules for the GML umented in Appendix C. simple feature subset; and 2. The schema should utilize the linear referencing standards outlined in ISO 19133 (Clause 6.6) for all linear referencing. 5.5 GML Encoding and Validation Creation of GML Application Schemas OGC is currently preparing an abstract test suite that will for TransXML enable TransXML schema developers to ensure that the first of these two requirements is met. Because of their focus on The TransXML schemas make use of the Open Geospa- GML, their test suites are likely to be more thorough and tial Consortium GML simple features profile, which is a complete than could possibly be developed under this proj- subset of GML. This subset was developed to simplify the ect. In addition, OGC is considering and is likely to recom- process of writing software that generates and parses the mend incorporating the relevant portions of ISO 19133 as GML/XML documents. The simple features profile is described part of GML, and is likely to maintain its test suites as GML in OGC document [OGC 05-033r24] (Copyright 2005 evolves. Therefore, it was determined that the TransXML Open Geospatial Consortium, Inc. Used with permission. project should not develop redundant validation software. All Rights Reserved. To obtain additional rights of use, visit Developers of future TransXML schema should make use of http://www.opengeospatial.org/legal/ which explains what the OGC test suites for schema validation. needs to be in the schema.) The GML application schema validator (Version 2.1.2) The Open Geospatial Consortium has made available a checks the schema's validity against Version 1.0 of the W3C program called ShapeChange which converts UML into XML Schema specification and Version 2.1.2 of the OGC GML. Documentation on the ShapeChange tools can be GML rules. The schema must be available on a web server found at: http://www.interactive-instruments.de/ugas/. The via a HTTP URL. The following checks are included in the ShapeChange tool was used to create an initial or partial cut validator: at each of the TransXML schema except for the bridge design and analysis schema. This last schema was created through a All feature type definitions must extend xmlns(gml=http:// separate process to ensure consistency with the existing Virtis/ www.opengis.net/gml)AbstractFeatureType or form a com- Opis XML report generator output (see Section 5.6 for fur- plex type that extends that type; ther information). A GML feature definition must not have a direct child ele- Experience with the ShapeChange tool was mixed. The ment that derives from xmlns(gml=http://www.opengis. tool makes certain assumptions about element namespace net/gml)gml:AbstractFeatureType; prefixes which did not always agree with the conventions A GML feature definition must not have a direct child ele- established for TransXML. For example, we use "xs" for all ment that derives from xmlns(gml=http://www.opengis.net/ W3C elements and nothing for the namespace of the schema gml)gml:AbstractGeometryType; and being defined. ShapeChange does the opposite. TransXML The schemas must define the schemaLocation for all import also has adopted a uniform order to elements in a schema file: and include statements that are resolvable from the source root element, alphabetized base property types, other prop- schema URL. erty types (also alphabetized), and finally alphabetized enu- merations and code lists. It was not apparent what order The OGC test suite also provides a GML instance document ShapeChange used. ShapeChange was useful in generating validator. This validator checks a GML instance document the enumerated and code list types, to reduce manual entry. against the GML 2.1.2 schemas and against the application