Schema Translation – OS Mastermap, but not as we know it Eddie Curtis, Snowflake Software, Greg Byrom, Richie Fyall GeoData Management Group Ordnance Survey 22 nd September 2005

Schema Translation - concepts XML schemas becoming ubiquitous Use of a GML schema (e.g. OS Mastermap) simplifies translation to other market sector specific XML schemas Process of translating from one schema to another often hard- coded, manual process Process can be automated using XML translation software Result is data in almost any market sector specific XML schema

Schema Translation – project objectives Objectives of the Schema Translation project were: Prove the concept of schema translation using OS MasterMap as the source Investigate technical feasibility & constraints of using XML translation software for this purpose Understand implications of presenting Ordnance Survey data using different target schemas Understanding implications for internal Ordnance Survey data management

Schema Translation – Process diagram Source database Product database Product Adaptor (Hard-coded) Target schemaSource schema Translation Engine

Schema Translation – target schemas Target schemas must be semantically similar to the source. E.g. a target schema designed for transport networks can use Integrated Transport Network (ITN) data as the source. Market sector specific schemas can be created, e.g. from Simple Features GML (OGC specification). More complex target schemas can be used to prove the translation process is not too limited by complexity

Target schemas chosen EuroRoads would be first choice, but no schema available. KML: Keyhole Markup Language for Google Earth. (Not GML) Simple Features GML: We created a simplified GML schema for both topographic and transport/routing data. GOS-TP (Geospatial One Stop - Transportation Pilot): Transport network schema. OKSTRA: Transport network schema for German road network.

Translating OS Mastermap GML

Translating OS Mastermap GML (Cont.) Some fields in OS Mastermap match directly to fields in target schema. Naming conventions may be different, however. Where a direct translation between schemas is not possible, various options are available: Build values for fields in target schema from multiple fields in OS Mastermap Constant values can be added XSLT style sheets – e.g. to calculate values such as date formats, or for more complex semantic translation Plug-in extensions for software (KML)

Translating OS Mastermap GML (cont)

ITN to OKSTRA translation

Example of output: OKSTRA A demonstration to validate output of OS Mastermap ITN data in OKSTRA schema… A view of OS Mastermap ITN data output to the GOS-TP schema

Problems/issues with Schema Translation Fully semantic translation not yet possible E.g. OKSTRA – German road classification different from UK road classification Requires XSLT style sheet – translate the semantics manually Target schemas not well developed – OS Mastermap more comprehensive than most

Problems/issues with Schema Translation Very few viewers at present for GML v3 data. OKSTRA and CityGML have their own viewers, but very limited. Values for mandatory fields in target schemas do not exist in source schema – limitation of the target schema E.g. OKSTRA – fields mandatory for legal reasons in Germany but not in the UK

Conclusions To do schema translation: Understanding of XML schemas is a necessity. Ability to analyse target schemas and decide which fields to match. Schema documentation is a necessity. OS Mastermap schema very well documented, others vary. Many XML schemas are still in research or development phases, especially market sector specific schemas. Only semantically similar XML schemas can be used as target schemas. Schema Translation is a flexible, useful tool for Ordnance Survey to produce data tailored to market requirements.

Contact for further information Customer Contact Centre Ordnance Survey Romsey Road SOUTHAMPTON United Kingdom SO16 4GU Phone: Fax: Web site: Eddie Curtis CTO Snowflake Software Tel:

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