Overview
ISO/TS 19157-2:2016 specifies an XML schema implementation for geographic data quality encoding. Derived from ISO 19157:2013 and the data‑quality concepts in ISO 19115‑2, this technical specification defines XML schema modules, namespace conventions, conformance rules and test suites to validate XML instance documents that encode data quality and metaquality information for geographic information (GI).
Key topics and requirements
- XML schema implementation: Formal XSD modules that implement the conceptual model of ISO 19157 and selected concepts from ISO 19115‑2 for encoding data quality in XML.
- Encoding rules and references: Follows encoding rules from ISO 19118, ISO/TS 19139, and the implementation approach from ISO/TS 19115‑3.
- Conformance and testing: Conformance framework aligns with ISO 19105; Annex A provides an abstract test suite for validating XML instances.
- Namespaces: Defined namespace pattern (http://standards.iso.org/iso/19157/-2/xxx/N.M) and modular namespaces (e.g., mdq, dqm, dqc) to group elements for metadata for data quality, data quality measures, and common classes.
- Core schema constraints:
- A property element instance SHALL have exactly one of: inline content (by‑value), an xlink:href (by‑reference), or a gco:nilReason (nil value).
- XML instances SHALL be well‑formed and valid against the schema in this document.
- Requirements classes for types:
- DQ_DataQuality instances require scope and report properties.
- QE_CoverageResult requires spatialRepresentationType, resultSpatialRepresentation, resultContentDescription, and resultFormat/resultFile values.
- DQM_Measure requires measureIdentifier, name, elementName, valueType, and a valueStructure when multiple values are present.
Applications and users
ISO/TS 19157-2:2016 is practical for:
- GIS developers and software vendors implementing metadata editors, validators, or data quality reporting tools.
- Data custodians, national mapping agencies, and geospatial data producers who need to publish standardized data quality metadata in XML.
- Standards bodies and integrators ensuring interoperability of data quality information across catalogs, web services, and data exchange workflows.
- QA teams performing automated conformance testing of geographic metadata using the normative test suite.
Benefits include standardized data quality encoding, reliable metadata validation, and improved interoperability of geographic information quality information.
Related standards
Keywords: ISO/TS 19157-2:2016, data quality XML schema, geographic information metadata, ISO 19157, ISO 19115-2, conformance testing, DQ_DataQuality, DQM_Measure.
