Abstract

Metadata

Author:	Brodaric, B., Journeay, M., Talwar, S., and Boisvert, E.,
Agency:	Geological Survey of Canada
Date:	1999
URL:	http://132.156.108.208/Cordlink1/

Intention

This variant was created in 1998 by Brodaric, Journeay and Talwar to support CORDLink, a virtual library project funded by the Geological Survey of Canada (http://cordlink.gsc.nrcan.gc.ca/cordlink1/ )..

Category

CORDLink (v5.2) is a conceptual model that is implemented using different database systems at several locations across Canada.

Summary

CORDLink (http://cordlink.gsc.nrcan.gc.ca/cordlink1/info_pages/English/dm52.pdf; Brodaric et al., 1999, http://pubs.usgs.gov/openfile/of99-386/brodaric1.html) derives directly from work done by Brodaric, Johnson, Raines, Hastings, and Wahl in a USGS-GSC-AASG data model working group that preceeded NADM. The CORDLink v5.2 variant extends that work to handle references to images and text and serve as a backend of a web portal for the geology of Canadian Cordillera. The CORDLink model has since been slightly revised by the addition of "support" tables to facilitate the interaction of the Geomatter user interface with the data model. Very slight changes were added to other implementations of CORDLink 5.2 (Hydrolink, GASL) to support multiple languages (Boisvert & Lauzière). The most recent version available (5.2.1) is an Oracle implementation that required small adjustments to comply with Oracle requirements in naming fields and referential integrity.

Diagram (PDF)

Comparison

Conceptual differences

CORDLink 5.2 diverges from NADM 4.3 in several ways. Most of the differences lie in the logical data model, as many concepts remain unchanged.. The differences include:
1. Sources are extended to include more than just maps, and hence the "source_type" attribute is required. Non map sources are specialised sources that are not connected to spatial objects, nor in some cases to any classification.
2. CORDLink 5.2 supports "subjects". The subjects are a hierarchical list of geoscience subject keywords extracted from GEOREF (database of bibliographic information in the geosciences, see <http://georef.cos.com/>). This list is used in the source, the image and the text tables to identify an overall subject.
3. Classifications can be linked only to 0..1 COA: In 4.3, a classification item (a legend item) could be linked to more than one COA (through the data_classification table). V5.2 limits this relation to a maximum of one.
4. COA and SOA share the same "pool" of attributes: COA and SOA attributes are not considered as being different things anymore. A "description" can be applied to either any COA (concept) or any instance (SOA). The 4.3 model supported 2 types of attributes, the COA attributes and the SOA (GIS) spatial attributes.
5. COA and SOA relations to their attributes can have attributes. It is possible to document the relation between a COA or a SOA and their attributes (which are variable), especially in terms of quality and proportions.
6. Metadata about attributes linkage are included. Since the CORDLink 5.2 documentation does not impose a definitive set of attributes for a COA, it is possible to alter the proposed set or even add more attribute types. A mechanism is included in 5.2 to document the location of the attributes and define their usage for a certain COA types (allowing a certain type of attribute to be added or not to a certain COA type). This means there is a "formal" way in 5.2 to expand the types of COA and related attributes the model can handle. It is also possible to expand SOA the same way. The technique allows a great level of flexibility and still provides the necessary constraints without hard wiring the model.

Physical and Logical differences

Source

The source table and related tables are quite similar, except for a few name changes and the addition of the source_type and subj_id (subject_id) field. The source_type field is related to a source_type look-up table while the subject field is related to a subject table and its supporting subject tree table.

Classification (Legend)

The classification tables are slightly different from NADM 4.3, as the same basic fields are distributed differently in scheme, classification and cartographic tables. In terms of wiring, the classification_scheme table bridges the source and the scheme_object tables (instead of being a look-up of the latter). Classifications have their own tree structure. A classification is related to a single COA.

COA

The implementation logic of COA and related attributes is different in NADM 4.3 and CORDLink 5.2. The 4.3 data model links the COA to specific COA table types and then to their attributes (COA->COA_type->Attributes). The 5.2 Model links the features by moving the COA table to the center (COA_type <- COA -> Attributes). In 4.3 the wiring of the data model imposes a constraint that controls which attribute is suitable for a certain COA_type, while 5.2 does not impose the constraint at the model level but at the metadata level (it's then possible to grant or revoke dynamically the attribute linkage).

Attributes

In NADM 4.3, SOAs and COAs have their own set of tables that describe them. In CORDLink 5.2, attribute tables for SOAs and COAs are merged into a common pool of shared descriptions..

The way the attributes are now modelled suggests a different cardinality for spatial objects. In 4.3, the implicit cardinality is 1 spatial object = 1 attribute record of a specific type (i.e. 1 polygon in the SHP file is related to a single row of attributes in an SOA table). For example, a single station having more than one structural measurement would require the creation of as many point objects (spatial objects) as there are measurements. In CORDLink 5.2, attribute tables shared between both SOA and COA require special mechanism for the relation. The linkage of attributes with either COAs or SOAs is done through "description" tables, which are essentially relational "bridges" or a "correlation tables". The COA_Description table matches a COA on one side and an attribute in any of the attribute tables on the other side. On the SOA side, the SOA table plays the same role (Appendix 1).

Example

See example in Appendix 2 (PDF)

The example is based on a legend description extracted from :

Harald Drewes. 1998,. ARIZONA. Geologic map of the Bartlett Mountain Quadrangle, Pima and Santa Cruz counties, Arizona, I-2624. Lat 31 deg 22'30" to 31 deg 30', long 111 deg 15' to 111 deg 22'30". Scale 1:24,000 (1 inch = 2,000 feet). Sheet 43 by 39 1/2 inches.

The text of the legend reads as follow :

Dacitic Vent Breccia (Miocene) -Light-medium-gray, finely porphyritic dacitic rock containing inclusions of Jurassic or Proterozoic granite and Jurassic rhyolite (welded tuff?) as much as 20 m in diameter. The subcircular outcrop mass of breccia probably is a volcanic vent or throat. A halo of strongly saussuritized rock 0.3 -0.5 km wide (delineated on map) surrounds this vent. The dacitic matrix consists of phenocrysts (25-35%, as much as 2 mm in length) set in a cryptocrystalline granular groundmass. Phenocrysts included albitized(?) plagioclase (12-18%), chloritized biotite (2-5%), uralized amphibole (2-10%), magnetite (trace to 2%), and apatite (trace). Quartz is present as a secondary mineral, filing vugs.