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Section 2: Introduction to the topic

2.1 Discussion of the tutorial use

2.2 How interoperability is improved through the use of this server/service

This document describes the GeoViQua data encodings for producer and user quality information. Information on new elements and the relevance of it can be found in this tutorial. We also have included some examples of good practice for their use.

2.2.1 Introduction to the producer quality model

The producer quality model is shown in Figure 1, and is more fully discussed in section 3.

PQM.png

Figure1. The GeoViQua producer quality model

The producer quality model introduces elements to record qualitative and quantitative quality information, and to identify resources (i.e. datasets) in order to relate metadata in hierarchical or other ways. The model extends ISO 1911511, 19115‐22 and 191573, adding means to report publications, discovered issues, reference datasets used for quality evaluation, traceability, and statistical summaries of quantified uncertainty.

2.2.2 Introduction to the user quality model

The user quality model is shown in Figure 2. It re‐uses some ISO quality and metadata elements, and elements of the producer model, but is far less strictly bound to existing ISO schemas.

UserQualityModel.png

Figure 2. The GeoViQua user quality model

1 http://www.iso.org/iso/catalogue_det...csnumber=26020

2 http://www.iso.org/iso/catalogue_det...csnumber=39229

3 http://www.iso.org/iso/iso_catalogue...csnumber=32575

The root element of the schema is the FeedbackCollection, which can hold zero or more FeedbackItems. An empty FeedbackCollection indicates, for example, a search for feedback where no relevant data was found.

A ‘FeedbackItem’ may4 'own' or 'hold' for example any combination of:

  • (optional) rating;
  • one or more user comments;
  • one or more reports of usage (including reports of any discovered issues);
  • citation of one or more publications;
  • a text description of the feedback subject;
  • text tags which might assist with topic‐based search and linking;
  • one or more quality overrides;

It must ‘own’:

  • one or more sets of details on the focus of the feedback;
  • a reference to at least one target of the feedback (a dataset, resource, etc.);
  • one user information describing the submitter of the feedback;

These components of user feedback are discussed in more detail in section 3.4.

2.2.3 Accessing the UML definitions for these conceptual models

Both the producer and user quality model have been formulated as UML diagrams which, as well as being viewable as online images (see above) may also be accessed using Enterprise Architect5. A file containing both models, as well as all supporting schemas, may be downloaded from the following URL.

http://schemas.geoviqua.org/GVQ/3.1....ViQua_v3_1.EAP

This UML defines all cardinality, extensions and relationships to existing ISO standards.

4 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 (http://www.apps.ietf.org/rfc/rfc2119.html)

               

5 A free version of Enterprise Architect with reading capabilities can be downloaded from

               

http://www.sparxsystems.com/uml_tool...ol/ea_lite.htm

2.3 References to associated videos, books, and other resources, when exist

2.3.1 Relevant ISO standards referenced and reused

The producer model in particular is designed to extend the existing practices of metadata generation, and thus wherever possible, widely‐accepted ISO elements used by INSPIRE and national institutions are employed. All of the schema documents discussed here can be accessed at http://schemas.geoviqua.org/

2.3.1.1 19115 / 19139 – Metadata

The 19115 metadata standard is extended in order to exploit existing and accepted conceptual models for citation, instrumentation, spatial and temporal extent, contact details, spatial data representations and other elements of the geospatial domain of discourse.

The schema documents referenced are the 19139 schema implementations of the 19115 specification. The 2007 versions hosted at schemas.opengis.net may be used, and the 2007 version is bundled with the schemas supplied as part of GeoViqua deliverable D6.1, for local reference.

(http://schemas.geoviqua.org/ISO/19139/20090316/).

However, there are several updates to the 19115 specification which have not yet been implemented in the available 19139 schema documents. These have therefore been added within the GeoViQua project as part of a separately‐referenced schema document, in the anticipation that these updates will ultimately be incorporated into the published schema implementations.

The specific updates concerned are as follows, and can be accessed at http://schemas.geoviqua.org/ISO/1913...15_updates.xsd

1. ISO 19115 includes a MD_Identifier object for associating identifiers with various objects in the metadata record6. The RS_Identifier extension of MD_Identifier (also part of ISO 19115) included several important additions (see Figure 3) because of the increased importance of namespaces in the XML and Web environments and because of ambiguity in how the namespace is actually defined in the CI_Citation associated with an MD_Identifier. These additions are to be incorporated into the MD_Identifier, but are not yet available in published XML Schema documents (XSDs). The importance and correct use of unique dataset identifiers is further discussed in section 3.5.1.

DataType.png

Figure 3. The new version of MD_Identifier (Source: https://geo-ide.noaa.gov/wiki/index....SO_Identifiers), with highlighting of new attributes added.

2. MD_AssociatedResource element of 19115 is ideal for giving details of any reference dataset which has been used as the benchmark for a quality assessment. It allows the dataset to be identified using an identifier, and the means in which it was used to be described using ISO codes (see Figure 4). This is also unavailable in published schema implementations and has been locally implemented. The use of the element is demonstrated in Sections 3.3.3 and 5.5.

MD_Asso.png

Figure 4: MD_AssociatedResource

Some of the modifications or extension to ISO19115 has been submitted to the ISO19115‐1 Matadata – Fundamentals (the new revised version of the Metadata that is under the review process. The modifications submitted and results of this interaction have been explained in the GeoViQua deliverable D1.7.

2.3.1.2 19157 – Data Quality

This standard is not approved yet but is in the final stages of the process. For our development purposes, we gained access to the advanced drafts. Only small changes are expected at this stage. The harmonised 19157 standard for data quality information has introduced several changes:

  • Separating attributes of the DQ_Element into three distinct objects: measure (optional), evaluation (optional) and result (required). This is illustrated in Figure 5, and is designed to solve problems with achieving appropriate repetition in the original schema.

DQ_Element19157.png

Figure 5. New components of the DQ_Element in 19157

  • Allowing a standalone report to be referenced from the DQ_DataQuality element, with a short abstract describing its content. This allows supplementary information outside the conceptual scope of the framework to be accessed. A standalone report is encoded as a new object, DQ_StandaloneReportInformation, and is referenced as a ‘report’ element of the DQ_DataQuality element, in the same manner that a normal metadata element would be referenced (see Figure 6). This allows linkage between ISO metadata and data quality information which does not fit the conceptual model of the available ISO schemas.

                 

ISO191157.png

Figure 6: ISO 19157 mechanism for standalone reporting

  • Introducing a metaquality element (see Figure 7) to record information about the representativity, homogeneity and confidence levels of the quality data itself. This allows users to assess the rigour and relevance of the assessments which generated the quality statement, and could thus be extremely important in assessing fitness‐for-purpose.

    ISO191157_metadata.png

Figure 7. ISO 19157 'metaquality' additions.

Since 19157 it has not yet been approved, the schema is not yet available in the form of published schema documents, so for practical implementation, as with the 19115 updates, a local implementation was produced. This is accessible at:

http://schemas.geoviqua.org/ISO/1915...ataQuality.xsd

This follows the specification in all regards, with the expectation that in the future, a reference to a published schema document may simply be swapped in in its place.

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