SDI Convergence - Global Spatial Data Infrastructure Association
SDI Convergence - Global Spatial Data Infrastructure Association
SDI Convergence - Global Spatial Data Infrastructure Association
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fication both of data and models. The usage of spatial data metadata for this purpose is<br />
a fundamental service within <strong>SDI</strong> and is in wide use (van der Wel, 2005; Stout et al.,<br />
2007; Nogueras-Iso et al., 2005). At this point there are many model registers supporting<br />
model search and discovery (i.e., NASA <strong>Global</strong> Change Master Directory (Website<br />
3), Freebase - Environmental Modelling Collection (Website 4), Catchment Modelling<br />
toolkit (Website 5)).<br />
At level 2 a deeper description of both information and models is required to assist their<br />
utilisation. For data and information in particular this includes metadata describing the<br />
genesis, quality and condition of the data resource. In the fields of Agriculture and NRM<br />
this metadata is of high importance as data often exists as a collection of data instances<br />
that have been produced by a number of projects and initiatives. These are<br />
often spread over time and may be subject to an evolving standard or improving collection<br />
methods and associated technologies. Unless there has been strong adherence to<br />
a data collection standard the specific instances in the collection may differ in subtle<br />
ways that can have a profound influence on their utility. At this level these differences<br />
are captured in the metadata which is often of a more technical nature. At present this<br />
type of metadata does not get much attention in metadata schemas (NIOS, 2004) and<br />
can be costly to collect. An exception is the emerging Numerical Model Metadata standard<br />
associated with climate modelling (Steenman-Clark et al., 2004). Stout et al.<br />
(2007) provide an example where the US Federal Geographic <strong>Data</strong> Committee (FGDC)<br />
metadata standard is being extended to support some of this type of metadata. At level<br />
2 the use paradigm for model metadata is changed. Rather than generally describing<br />
the model itself emphasis is placed on storing contextual information about the modelling<br />
activity and how to implement. To support effective model use not only are technical<br />
descriptions of the inputs and description of how to execute the model important but<br />
understanding where and who implemented the model is extremely useful. This can<br />
benefit to prevent duplication in modelling effort. In contrast to level 1 there are not<br />
many tools that effectively address and use model metadata at this level. Most approaches<br />
to date are associated with theme based modelling groups and a good example<br />
is the ‘Earth System Curator’ and its prototype database used by climate modellers.<br />
In this context the record of model activity is confined to the community of interest.<br />
This prototype has the stated objective to “store metadata related to model runs and<br />
datasets” but is still under development. The authors have not yet found published<br />
model metadata systems recording details of model instances spatially (other than the<br />
MIKE system described herein). Practical support for this function requires user-friendly<br />
and efficient approaches to the spatial registration of these instances. At level 2 there<br />
are opportunities to link model and data metadata repositories (for those models with<br />
stable or fixed data inputs) and support queries informing understanding of spatial data<br />
availability for modelling. These approaches require a common referencing scheme for<br />
datasets in both registers. This is a key component within the case study described in<br />
the following section.<br />
At the third level the emphasis for metadata shifts to record details that can support associated<br />
processes both for models and data. In the data area examples include metadata<br />
to support publication and transformation of data such as in web based mapping<br />
or even workflows associated with data such as managing collection by third parties<br />
(Stout et al., 2007). In relation to models this metadata serves as a base to underpin<br />
applications for automated model processing or pre-processing of data for models.<br />
Current development in this area is largely confined to process models in remotely<br />
sensed data (Jianto et al., 2003) or in climate modelling. The development of metadata<br />
in this area is a crucial part of an <strong>SDI</strong> to support automated publication of data and<br />
models. Where the metadata is extended to store processing instructions, algorithms or<br />
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