XMML – A STANDARDS CONFORMANT XML LANGUAGE FOR GEOLOGY FEATURES

In order to engage in a productive discourse a community must adopt shared definitions for the items of interest to that community. When the information items are imported and exported from automated processing software, then the models and serialised instances must be expressed rigorously and precisely. Many notations are available. Of particular interest are the object-oriented Unified Modelling Language (UML), and the eXtensible Markup Language (XML) with its associated schema languages, especially the W3C XML Schema Language (XSD). Some features of XSD (type derivation, element substitutability) are closely related to object-modelling capabilities (inheritance, polymorphism), so it is possible to use XSD directly as a conceptual schema language. Conversely, XML can be used to instantiate objects defined by UML classes.

Standard web-service interfaces to geospatial information have been developed by the Open GIS Consortium (OGC). Geography Markup Language (GML) is a key element in these interfaces, acting as the basis for XML serialisation of data payloads. However, GML is a meta-language, providing components and a basic data model for use in community-specific application languages. In order to take advantage of OGC Web Service interfaces, therefore, a community such as geoscience must express its data model as a GML Application Language.

We have been developing the eXploration and Mining Markup Language (XMML) in this vein. XML technology lends itself to modularisation, so XMML is being developed progressively, according to the needs of project sponsors. These include geological surveys and mines departments, mining and exploration companies and service providers, and R&D organisations. XMML is being deployed for interprocess-communication, inter-organisational data transfer, and archiving. Many of the components are relevant to generic geology and geophysics, and are not solely artefacts of mineral exploration.

In developing XMML we are using both XSD and UML for design and documentation. GML uses a particular style of XML, which requires that the UML must also follow certain idioms, particularly concerning associations. However, providing that these rules are followed, it is relatively straightforward to incorporate additional components for which UML models are available into XMML.