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Annex A: Summary of Recommendations

Attribution Subgroup

The Attribution Subgroup recommends extending the current CDB XML metadata to add the NAS metamodel capabilities that are currently not supported. The CDB core conceptual model should not mandate any particular data dictionary or content, but rather provide the conceptual and logical metamodel for describing any ISO 19109 compliant application schema to the maximum extent practical. There should be no technical reason why one could not develop an extension profile for CDB for any particular data dictionary that complies with ISO 19109.

  • Adopt NAS-compliant logical entity-attribute model for CDB X with extensions for CDB use cases

    • Store all aspsects of feature and attribute dictionary in single SQLite file for portability and runtime performance

    • Use GGDM 3.0 as the initial starting point for definitions to populate CDB X data dictionary

    • Match up remaining CDB non-GGDM feature types and subcodes with latest NAS definitions where possible, matching subcodes to attributes where relevant and adding missing enumerant values where necessary (with associated NCV vocabulary)

    • Augment NAS definitions with other open standards and new development

      • Match up missing maritime definitions to DGIM followed by IHO S-100 where possible, define NCV vocabulary for such integrated definitions

      • Match up missing aeronautics definitions to DGIM followed by AIXM where possible, define NCV vocabulary for such integrated definitions

      • Coordinate with OGC, NGA, and STE OWT to develop replacement building interior data model incorporating IFC/BIM, CityGML, IMDF, and other open standards

      • Coordinate with OGC, NGA, STE OWT, and civilian environment agencies to develop detailed data model for vegetation

      • Create data model and vocabulary for material and light point definitions and capture into existing material and lightpoint libraries

      • Define NCV vocabulary and NAS-compatible entity and attribute types for CDB feature types and subcodes totally missing in all other standards

    • Remove CDB feature subcodes entirely; migrate to existing and new feature and attribute types instead in NAS-compliant structure

    • Define entity types for CDB datasets and define "aggregation" relationships from feature types to containing datasets

    • Capture feature-level, dataset-level, and database metadata as NAS-compliant attribution meeting the NSG Metadata Foundation (NMF) and ISO 19115

    • Define functional role domains and create mechanism to organize attribution by domain for tailoring to runtime devices

  • Delegate entity and attribute physical encoding choices to vector and 3D model containers instead of specifying globally

    • Deprecate extended attributes entirely, to be removed in CDB X

    • Delegate containerization of entity types (one per table, multiple in same table specified by F_CODE attribute, etc.) to vector and model containers

    • Delegate decision whether to use class or instance attributes to individual vector and model containers rather than global data dictionary

    • Delegate decision of whether to use FACC-like codes, NAS labels, or natural language names for entity types, attributes, and values to vector and model containers

    • Delegate decision of whether to flatten complex feature relationships and attributes used GGDM attribute prefixing to vector and model containers

    • Delegate decision of whether to flatten multi-valued and range-valued attributes using GGDM attribute prefixing to vector and model containers

    • Specify minimum and maximum cardinality of multi-valued attributes in feature and attribute dictionary, allow containers to use a lower maximum if using GGDM attribute prefixing encoding

  • Define backward-compatible extensions in CDB 1.3 to add constructs necessary to move toward NAS-compliant attribution

    • Capture proposed NAS-complaint replacement feature dictionary in existing CDB metadata XML with necessary extensions

    • Only use feature subcode 000 in replacement dictionary and deprecate use of feature subcodes to be removed in CDB X

    • Add mechanism to mark numeric attributes as interval ranges (existing non-upgraded clients should see still attribute as single-valued and read mean value from associated unsuffixed attribute, use suffixed attributes for deviation and closure for upgraded clients to read)

    • Add minumum and maximum cardinality elements for attribute definitions to specify mininum and maximum element count for multi-valued attributes (existing non-upgraded clients should just see attribute as scalar base value and will only read the first value from associated content, will see ordinal-suffixed attributes as separate attributes)

    • Add list of valid attributes to datasets in CDB 1.x metadata XML files to match existing human-readable specification

    • Add list of valid enumerants for each attribute in CDB 1.x CDB_Attributes.xml file to match existing human-readable specification

    • Add list of valid attributes for each entity type as extension to CDB 1.x Feature_Data_Dictionary.xml to implement NAS-compliant per-entity attributes

    • Update CDB 1.x CDB_Attributes.xml to allow specifying text pattern constraints through <Pattern> element and text codelists for text attributes via <Codelist> element

    • Update CDB 1.x Feature_Data_Dictionary.xml for each feature to specify its generalization (base) entity type via <Generalization> element

    • Update CDB 1.x Feature_Data_Dictionary.xml to add <Aggregation> element to define additional associated category for an entity type, or parent category for a category

    • Existing category and subcategory XML structure will add implicit definitions and aggeregation links for the category/subcategory items as used by CDB 1.0 for model storage

Recommendation 1 Extended Attributes - Version 1.3 The subgroup discussion on this topic is titled: Should Extended Attributes be preserved at the logical data model level? The suggestion is that the CDB SWG discuss this issue and possible solution as a possible change for CDB version 1.3. Some additional testing may be required to determine if this capability can be added to version 1.3 or not.

Recommendation 2 Attribute default values - Version 1.3 The subgroup discussion on this topic is titled: Attribute Default Values #32. The recommendation is that Defaults.xml can be used to define global attribute defaults as well as per-dataset defaults. Doing per-entity defaults would be a straight forward extension that could be proposed for CDB 1.3 as a transition path. The subgroup suggests that the CDB SWG discussion this for possible inclusion in version 1.3. A change request for this approach to specifying default values is also suggested.

Recommendation 3 Attribute Terms - Version 1.3 The subgroup discussion on this topic is titled: Capture Attribute Terms (Enumerants) in Metadata #31. Attributes describing qualitative values are present in CDB 1.2 and the list of valid values for each attribute are documented in the human-readable specification with both the vocabulary term name and its integer numeric value (index). However, the machine-readable XML metadata does not contain any of this information and treats these attribute types as raw integers with only a minimum and maximum value constraint. It may make sense as a transition path to update CDB 1.3 to define additional XML elements in a backward compatible way to capture these definitions from the existing specification into the machine-readable XML metadata. The conceptual model in the CDB 1.2 specification does align with how GGDM treats such attributes, so there is no fundamental incompatibility, and the proposed CDB X dictionary design accounts for properly tracking the terms for qualitative attributes in a machine-readable way in SQLite.