Data Framework Technical Sub-Committee
and the
ICSM Harmonised Data Model

Background

Australia and New Zealand are major users of spatial information.  In both countries, a multitude of custodians maintain an extensive range of data sets, in a variety of formats, for a wide range of applications.  Individually, the data sets satisfy an identified need and provide benefits to their custodial agencies.  Despite increased harmonisation over recent years, these still collectively exhibit a lack of homogeneity, inhibiting their integration into a national datasets.

The lack of homogeneity becomes a problem when gathering data for national or regional projects.  A project's implementer is faced with the expensive and time-consuming task of obtaining consistency from fragmented and heterogeneous data sets.  The absence of uniformity is also an inhibitor to the development of national on-line applications.  This ultimately results in economic loss to data users and suppliers alike.

There are now two versions of the ICSM Harmonised Data Model:

1. The first version which was released in 2000


2. The 'next generation' version, released in 2008

While the 2008 version of the ICSM Harmonised Data Model represents the current thinking of data modelling, components of the 2000 version are still relevent to the harmonistaion debate.

Introduction

The Harmonised Data Model (HDM) consolidates the data models for the Australian Spatial Data Infrastructure (ASDI) fundamental data sets being collaboratively sponsored by ICSM and its members.  At present, the HDM incorporates cadastre, topography, place names and street address.  It is intended to add hydrography at a later date.

The following should be noted:

• The primary objective of the HDM is to facilitate the compilation of national data sets from data supplied by jurisdictions.  Accordingly, only classes, attributes and relationships that have significance at the national level are included.  It should be noted that the HDM is capable of extension to accommodate local or jurisdictional needs.  Thus organisations can use components of the HDM as the foundation for local models, supplementing the classes and attributes as required.



• A further objective is to achieve consistency among the thematic ICSM data models, both as regards content and presentation.  It seeks to break down the 'silo' approach by identifying elements that are common to all themes.  Each class only explicitly includes attributes that are unique to that class.  Attributes that are common to several classes are accommodated through inheritance relationships.



• The HDM is conceptual in nature.  It is implementation-neutral but capable of being translated into implementation-specific profiles or products (for example, database or transfer schema).



• The HDM is presented as a hierarchy of models to assist distribution and interpretation.  At the highest level, the model illustrates the common and thematic packages, their dependencies and interdependencies.  At the lower levels, it illustrates the composition of the individual themes, allowing each theme to have different variants (for example, Cadastral Heavy and Cadastral Lite).  It also allows different themes to pursue different objectives and development philosophies without the model appearing internally inconsistent.



• The HDM has been prepared using Unified Modeling Language (UML).  The adoption of UML as the data modelling language, applied according to the rules and conventions set out in ISO 19103.  Extensible Markup Language (XML) has been adopted as the encoding mechanism for the transfer of spatial data.  It is assumed that users have some knowledge of both UML and XML.

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Compliance with International Standards

The HDM has been developed following the principles and methodology of ISO/TC211 – Geographic Information and the various standards they have developed.  These standards are now being used by the geospatial community to maximise interoperability and accessibility of data and services.  The principle standards used to develop the HDM were:

• ISO 19103 – Conceptual Schema Language covers the language, rules and guidelines required to achieve implementation neutral models for geographic information.



• TISO 19104 – Terminology provides the guidelines for collection and maintenance of terminology in the field of geographic information.  A 'terminology and definition spreadsheet has also been developed to assist the monitoring and harmonisation of these terminologies by ISO/TC211 and its working groups.



• ISO 19107 – Spatial Schema describes the spatial characteristics or attributes of geographic features and a set of spatial operations consistent with these schemas.



• ISO 19108 – Temporal Schema defines the concepts needed to describe the temporal characteristics of geographic information as they are abstracted from the real world.



• ISO 19109 – Rules for Application Schema defines the rules for the application schema, including the principles for classifying geographic objects and their relationships to application schema.



• ISO 19110 – Methodology for Feature Cataloguing covers a basis for the description of packages of geographic information enabling access to a distributed network.



• ISO 19111 – Spatial Referencing by Coordinates defines the conceptual schema for the description of spatial referencing by coordinates and the minimum data required to define one, two and three dimensional coordinate reference systems



• ISO 19118 – Encoding covers the encoding rules for how to map from the implementation neutral UML models to a corresponding representation of data according to these models in XML.



• ISO 19119 – Services define the implementation specific profiles for the implementation neutral models, ensuring that there is well-defined mapping between these to ensure interoperability between different implementation platforms.

As further geospatial communities develop their own HDM’s it is anticipated the ICSM HDM will continue to be refined, ensuring alignment and consistence within the community.

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Technical Standards - The Harmonised Data Framework

The Harmonised Data Framework has been developed by ICSM to provide a cohesive, standards-based framework for the harmonisation of ICSM-sponsored ASDI datasets.  The framework has been developed to promote consistency in the management and transfer of spatial data and forms part of ICSM's ongoing commitment towards the development of the ASDI.

The framework's intended applications include:

• The uniform description of digital information within a single spatial theme
  The framework will serve as the basis for the consistent description of digital spatial information in distributed ICSM-sponsored fundamental data sets (for example, the spatial cadastre data sets maintained by the various jurisdictions) enabling them to be bought together for national projects.
  
  
• The integration of the digital information representing different spatial themes
  The framework will facilitate integration of data from different spatial themes (for example cadastre and topography) by utilising common underlying data structures and conventions, effectively breaking down the 'silo' approach that has traditionally prevailed.
  
  
• The provision of an agreed model for the specification of digital spatial databases
  The framework's data model will facilitate the specification and development of digital spatial databases.
  
  
• The provision of an agreed model for the specification of digital data transfers
  The framework's data model will enable data transfers to be accomplished through specification of the data elements and the data structure.
  
  
• The testing or specification of new technology requirements
  The framework will be useful as a test bed for evolving data management technologies, such as unique feature identifiers, audit trails for changes (history) and feature level metadata.

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