string

boolean

integer

double

anyURI

gpml:featureId

• GPML Feature Ids are the unique identifiers used for anything with a gpml:featureId[1] identity property, i.e. anything that derives from gpml:AbstractFeature. They must be unique for every feature, generated at creation time and remain unchanged for the lifetime of the feature.
• As an example, the unique id process used by GPlates draws from several sources of uniqueness, including Local time, Internal incrementing integer from this session, User id, Hostname, and Process Id. For example: GPlates-2263390205.0-jboyden.aurora.28095. Note that this is only an example of the process GPlates uses to create a unique identifier - the GPGIM only specifies that the id must be unique and remain constant for every gpml:Feature.
• The final featureId string should be restricted to the characters that are acceptable for XML Ids: http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/#Id

gpml:revisionId

• GPML Revision Ids are the unique identifiers used for the specific revisions of gpml:AbstractFeatures. They must be unique for each revision, generated at revision creation time.
• The final revisionId string should be restricted to the characters that are acceptable for XML Ids: http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/#Id

gpml:plateId

• Unique Id for a group of features that rotate in unison. Used in all ReconstructableFeatures via the .reconstructionPlateId property. See also TotalReconstructionSequence and AbsoluteReferenceFrame. They are represented by an unsigned long integer.

xs:any

gml:Point

gml:TimeInstant

gml:TimePeriod

gml:LineString

• gml:LineString is here as a placeholder only; in the GML schemas, properties such as centerLineOf will use gml:_Curve, although we expect to be dealing with LineStrings primarily.
• Note that the GPGIM is not GPML; The primary purpose of this document is to be the information model for GPlates, but not get tied down to one particular implementation of that model (e.g. XML, C++). Hence, it does not authoritatively talk about structures external to the GPGIM.

gml:Vector

gml:Polygon

gpml:measure

• maps to gml:MeasureType, which extends double and adds the requirement for a uom attribute indicating the units used.

gpml:angle

• represents an angle measurement. maps to gml:MeasureType, which bestows the ability to use the uom= attribute on the property, which in this case will likely be (degrees)

gml:_MetaData

gml:_Geometry

gml:AbstractFeature

• Note: all the properties listed here are for convenience only; we inherit many properties upstream from GML, useful things like gml:name and gml:description. There are many more that are not listed here which may come in handy.
• For example, there are two attributes (not properties) which will be essential for GPlates:
• srsName= For indicating the geocentric/geodetic ellipsoid approximation of the earth, for the coordinates used by geometry of this Feature- i.e. WGS84.
• frame= For indicating the geological time scale that was used to determine temporal position of this Feature. I believe we'll actually be using the 'frame=' attribute in gml:TimePeriod.{begin,end} or gml:TimeInstant.timePosition

• contains external gml:_MetaData[0..*] gml:metaDataProperty
  • The gml:metaDataProperty can contain almost completely arbitrary markup, thanks to the use of <xs:any>.
• contains external string[0..1] gml:description
  • Again, a 'hidden but useful' property inherited from GML.
• contains external string[0..*] gml:name
  • More than one gml:name can be assigned, the distinction between two names being handled by the 'codeSpace=' attribute of gml:name.
  • gml:name is actually found in the gml:AbstractFeatureType side of things, I just include it here so these 'hidden but useful' properties can be shown.

gml:AbstractFeatureCollection

gml:AbstractMetaData

gml:AbstractGeometry

FeatureCollection

- This is the root element for GPML data files, and is the way GML groups all other Features together. It contains these features via the gml:featureMember property.

• attribute string version

• contains external AbstractFeature[0..*] gml:featureMember
  • We inherit a property similar to this from gml:AbstractFeatureCollection. In the case of GPML we will be filling it with anything that derives from gpml:AbstractFeature, although there's nothing stopping other GML-compliant features from being bundled up with our own.

AbstractFeature

- Highest-level abstract parent of all GPML Features.

• contains const gpml:featureId[1] identity
  • GPlates enforces a mandatory unique Id for each Feature. See gpml:featureId for more information.
  • gml:name with a specific codespace was considered, but in this case we want to ensure specific Features have such an Id.
• contains const gpml:revisionId[1] revision
  • All GPlates Features also have a revision Id. When a feature is modified by a user, it gets a new revision Id, and its list of superseded revisions is updated. This way we can do some important book-keeping to help us in situations where multiple feature collections are loaded/modified/saved/unloaded.
• contains gpml:revisionId[0..*] supersededRevision
  • This lists all revisions of this feature that were superseded by this one. This is a more accurate way of keeping track of the past, older revisions of a feature.
  • It will be purged on occasion to ensure files do not get bloated from many small changes. Newly superseded revisionId s get unshifted onto the front/head of the list, older ones are at the end/tail of the list.
  • a simple linear 'version number' would fail if a feature collection was concurrently modified by multiple users and then merged.
• contains OldPlatesHeader[0..1] oldPlatesHeader
  • Since a Feature in GPML will often correspond to a PLATES polyline (if a PLATES file was the original source of data), we include an optional reference to a Plates-compatible header object. This is used to keep metadata around if we import from a PLATES data file.
• contains string[0..*] subcategory
  • attribute string codeSpace
  • Every gpml:Feature can optionally have one or more subcategories assigned to it. These are free-form text strings, and behave very similarly to the gml:name property; they also possess a 'codeSpace=' attribute to indicate what convention was used when assigning this subcategory to this Feature.
  • Use of the .subcategory property is entirely optional, however it is useful in several situations. There are many possible subcategories of real-world:Features, and these are highly subjective, depending on scientist, dataset, and area of research. Permitting arbitrary subcategorisation in the GPGIM has two benefits. One, GPlates can to continue to treat those real-world:Features as the appropriate gpml:Feature since any subcategory must have the same properties as the parent gpml:Feature. Two, it allows the scientist to have a finer grain of control over the categorisation of those real-world:Features without messing around with XML trying to extend the GPGIM.
  • An example: Seamount s and Guyot s. A Guyot is a special case of Seamount with a flat top. Functionally, they are identical. A problem arises; do we create a GPGIM feature for both of them, or just use Seamount for both cases? Some scientists and datasets may not care about the distinction, and wish to treat everything as a gpml:Seamount without being forced to go over the data and classify everything. On the other hand, a "Guyot Expert" would be very interested in the distinction between the two. The .subcategory property allows you to do this, without forcing you to.
• contains KeyValueDictionary[0..1] shapefileAttributes
  • As a large amount of data may be imported from Shapefiles, and there is not always an obvious way to map from (arbitrary) shapefile attributes to GPML property names, the user may need to set up a mapping that defines which shapefile attributes should be mapped, and the GPML property they are mapped to.
  • For example, the user may have a data set with "PLATEID" and "NAME" shapefile properties - these need to be mapped to the Feature's gpml:reconstructionPlateId and gml:name properties. Storing the mapping is important so that data can be returned to the original shapefile attributes later.

TimeVariantFeature

• TimeVariantFeature is one of the parents to the majority of commonly used gpml:Features.
• Most, but not all, features will ultimately inherit from our gpml:TimeVariantFeature in order to have the .validTime property. In contrast, features deriving from InstantaneousFeature require a TimeInstant rather than a TimePeriod, and they obtain this via the .reconstructedTime property.

• contains gml:TimePeriod[0..1] validTime
  • The validTime parameter defines the position of this feature on the geological timescale.
  • Some Features may only exist between (say) 120Ma and 100Ma, others will be represented as a series of distinct Features, i.e. a MidOceanRidge at (lat,long) between 200Ma-160Ma and another MidOceanRidge (which happens to model the same physical thing) at (lat,long) between 160Ma-0Ma, perhaps due to it having radically different properties. Generally, it is preferable to use GPML's time-dependent properties where applicable, but since we will be importing PLATES data, this 'slicing' of features will be commonplace in real datasets.
  • Note that if a gpml:Feature is a ReconstructableFeature, it might potentially have more gml:TimePeriod s recorded in its .reconstructionPlateId property, as it is a time-dependent property. The validTime that we specify here should still be used as the master indication of the Feature's lifetime.

InstantaneousFeature

- "Snapshot" version of GPML Features, defined at a specific time

• Most of the ReconstructableFeature tree is copied here. Instantaneous versions of gpml:Features are designed for export to other programs, which would have difficulty doing reconstructions themselves.
• These features have different properties to their Reconstructable counterparts. Aside from the "big one" of not being rotatable via the action of Finite Rotations, their geometry is defined in terms of a specific time (.reconstructedTime) rather than being defined in present-day terms. This distinction also becomes more important with time-variant property values.
• In comparison to ReconstructableFeature:-
• - must be defined for only an instant.
• - must have its geometry specified in its time-of-definition position (the time-of-definition may or may not be the present-day)
• - will not have a gpml:reconstructionPlateId
• Note, No properties of an InstantaneousFeature will be time-dependent!
• Like ReconstructableFeature, InstantaneousFeatures should have at least one geometric presence.
• As InstantaneousFeatures do not have a reconstruction plate ID property, they will be given a default reconstruction plate ID of 0 for display purposes.

• contains FeatureSnapshotReference<TimeVariantFeature>[0..1] derivedFrom
  • an optional link to the ReconstructableFeature this Instantaneous snapshot was taken from, for historical interest.
• contains gml:TimeInstant[0..1] reconstructedTime
  • the TimeInstant corresponding to the moment this InstantaneousFeature was converted from its Reconstructable original.
  • Normal GPlates Features store their geometry in present-day coordinates, and store reconstruction information to rotate them into paleo-coordinates. However, for exporting data into other GPML aware programs, i.e. GMT, it is necessary to do the rotations on behalf of the external application. The .reconstructedTime property of the Instantaneous feature records what time this Feature was reconstructed to by GPlates, (in Ma or whatever 'uom' and 'frame' you want in the TimePeriod).
• contains gml:TimePeriod[0..1] validTime
  • Instantaneous features only really exist for a single instant, the TimeInstant in the reconstructedTime property, set when a snapshot is made of a ReconstructableFeature. The 'TimePeriod validTime' property of the ReconstructableFeature is no longer applicable.
  • However, the original information about the features' lifespan is still useful information. Isochrons in particular measure their age as their time-of-appearance. This information would be lost in InstantaneousIsochron snapshots unless the information is copied to this .validTime property.
  • This property may at first glance appear to be identical to TimeVariantFeature.validTime, and it is true that the value of this property should be the same; however it serves a different purpose (useful record of original data) and is in fact an entirely different .validTime property with a TimePeriod value.
• contains gpml:plateId[0..1] reconstructedPlateId
  • in the spirit of not throwing away information, the plateId at time of conversion to an InstantaneousFeature type is recorded here. Unlike ReconstructableFeature.reconstructionPlateId, this is not a time-dependent property, and will only ever refer to one gpml:plateId.

ReconstructableFeature

- Parent of all GPML Features we may want to associate with a plateId and are reconstructable.

• A ReconstructableFeature may be rotated relative to another ReconstructableFeature by the action of Finite Rotations (Inside a TotalReconstructionSequence)
• In comparison to InstantaneousFeature:-
• - might be defined for only an instant
• - must have its geometry specified in its present-day position
• - must have a gpml:reconstructionPlateId
• ReconstructableFeatures should have at least one geometric presence.

• contains ConstantValue<gpml:plateId>[1] reconstructionPlateId
  • The plateId to use for reconstruction purposes. This property is a time-dependent one, but presently only supports a ConstantValue gpml:plateId.
  • In future releases, this is expected to be expanded to use a PiecewiseAggregation of multiple ConstantValues rather than a single ConstantValue, allowing different gpml:plateIds to be used varying through time.
  • Any feature which does not have a reconstruction plate ID property will be given a default reconstruction plate ID of 0. This will affect InstantaneousFeatures, and any other features, which don't have reconstruction plate IDs, whose geometries should be displayed.
  • Time-Dependency: Will later become a PiecewiseAggregation<gpml:plateId>.
• contains FeatureReference<ReconstructableFeature>[0..*] truncatedSection
  • Optional references to other Features that the user has indicated are supposed to be the same feature. While GPlates will treat each individual gpml:Feature separately, it is intended as a reminder that this Feature is part of a larger whole.
  • A common problem in PLATES datasets is the lack of any deformable geometry. This is often hacked around by creating multiple 'features' for the same real-world thing, for example, an Isochron getting subducted might have have been 'cut up' into multiple PLATES 'IS' features, to simulate the Isochron slowly disappearing. One day, this property will be used by a magical algorithm to undo all the 'cutting up' of features done in data sets for the purpose of hacking deformable geometry into PLATES.
  • Another example of this property in use is FractureZone.

TopologicalFeature

• In comparison with ReconstructableFeature and InstantaneousFeature :-
• - does not have geometry of its own
• - should be able to exist for more than an instant, so it is not really an "instantaneous" feature
• JB: An instantaneous plate boundary doesn't really need all the topological linking, since instantaneous features are primarily intended for export the only argument for maintaining the topological information is the usual "not throwing away information" argument, and the topological information could be maintained just as well by an optional reference to a topological plate boundary instance.
• JB: A topological plate boundary doesn't need any of the reconstruction timeline stuff, since the whole key to its existence is that it borrows its geometry from other features, which will be reconstructable, and thus will have their own reconstruction timelines.

TangibleFeature

• An 'Instantaneous' copy of this class exists, InstantaneousTangibleFeature.

ArtificialFeature

• In contrast to TangibleFeature, this deals with geometry that has been arbitrarily created, or possibly derived from a TangibleFeature. For example, InferredPaleoBoundary is a plate boundary that is assumed to have existed, even though it has long since been subducted under the surface. OldPlatesGridMark is a sequence of lines defined in PLATES data files for annotation.
• An 'Instantaneous' copy of this class exists, InstantaneousArtificialFeature.

PropertyDelegate<T>

- Reference to the value of a property belonging to a remote gpml:Feature

• A GPML-specific way to refer to a LineString property inside a Feature. In later versions of PropertyDelegate, this could be an XPath (or the various other X.. technologies) to the LineString itself, or some way to refer to the (Feature + appropriate property name). Most likely, the property we will be interested in referring to is "centerLineOf", but there could be others.
• This is a single tag, and has special properties to point to the feature and property we are interested in.
• This is so we don't paint ourselves into a corner later on. It's completely opaque to GML, and doesn't have quite the same potential for chaos as xlink:href does.

• contains const string[1] valueType
  • The stringified type of geometry, structural type etc that this PropertyDelegate can dereference to, as expressed through the template-like "T" parameter. This template parameter passed to PropertyDelegate from another property is a hint as to what types are expected when dereferencing.
• contains gpml:featureId[1] targetFeature
  • The gpml:featureId that uniquely identifies the gpml:Feature containing the desired property.
• contains string[1] targetProperty
  • Accessing a single property that is the direct child of the .targetFeature is accomplished by setting .targetProperty to the name of the property, such as "centerLineOf"
  • Accessing a nested property inside some complex Structural Type is a little more difficult. PropertyDelegates 1.0 will support a simple XPath-like syntax using "/*/" as a separator to specify the path. Example: "gpml:someProperty/*/gpml:someOtherProperty"
  • In PropertyDelegate 1.0, .targetProperty will start off being supported as a limited subset of an XPath expression.

FeatureReference<T>

- Reference to a remote gpml:Feature

• contains const string[1] valueType
  • The stringified type of Feature that this FeatureReference can dereference to, as expressed through the template-like "T" parameter. This template parameter passed to FeatureReference from another property is a hint as to what types are expected when dereferencing.
• contains gpml:featureId[1] targetFeature
  • The gpml:featureId that uniquely identifies the desired gpml:Feature.

FeatureSnapshotReference<T>

- Reference to a remote gpml:Feature (specific revision)

• Used by InstantaneousFeature to supply a potentially-useful reference to the TimeVariantFeature that the Instantaneous snapshot was taken from.

• contains const string[1] valueType
  • The stringified type of Feature that this FeatureSnapshotReference can dereference to, as expressed through the template-like "T" parameter. This template parameter passed to FeatureSnapshotReference from another property is a hint as to what types are expected when dereferencing.
• contains gpml:featureId[1] targetFeature
  • The gpml:featureId that uniquely identifies the desired gpml:Feature.
• contains gpml:revisionId[1] targetRevision
  • The gpml:revisionId that uniquely identifies the specific revision of the gpml:Feature this FeatureSnapshotReference should resolve to.
  • If the specific revision can not be obtained, this FeatureSnapshotReference will be unresolvable.

KeyValueDictionary

- Dictionary mapping arbitrary key names to values

• Used in the gpml:shapefileAttributes property of AbstractFeature. This allows data which has been imported from shapefiles to retain knowledge of the shapefile attribute mapping that was used during import.
• For example, the user may have a data set with "PLATEID" and "NAME" shapefile properties - these need to be mapped to the Feature's gpml:reconstructionPlateId and gml:name properties.
• Storing this mapping allows for the data to be returned to its original form, or for the user to view the mapping which was used and apply the same conversion to additional shapefiles.

• contains KeyValueDictionaryElement[1..*] element
  • A sequence of dictionary elements, each representing a single row of the mapping table.

KeyValueDictionaryElement

- Single row of KeyValueDictionary table

• contains string[1] key
  • The name of the key we are mapping - for instance, when storing shapefile attribute mappings, the name of the attribute, e.g. "PLATEID1".
• contains const string[1] valueType
  • The stringified type of value that this KeyValueDictionaryElement holds in the .value property. For example, "xs:double".
  • Note that "xs:double" in the example is dependent on the current alias of "http://www.w3.org/XMLSchema-instance" being "xs". It could also be "xsi", or any other alias, depending on the document's namespace settings.
• contains ANY[1] value
  • The raw value of this map entry. Note that it is defined to be of any type. Parsers should be able to read the valueType property to determine the run-time type of this property, in much the same way that the template types are used in TimeDependentProperty (for example, ConstantValue)

OldPlatesHeader

- Metadata that all gpml:Features can have, inherited from old PLATES data files.

• For preserving backwards compatibility and not "throwing away" information, if the original files came with PLATES header info, we can include them here and reference them in each AbstractFeature that is associated with that original PLATES file.
• Rather than use the traditional gml:.metaDataProperty path, I'm making this a seperate entity, if we want to do the full blown GML meta data thing later, there's nothing stopping us, but a simple solution for now is just to have it as an optional property in every AbstractFeature.
• It isn't immediately obvious if this structure should inherit from anything, I'm just making a stand alone structural type, it inherits from nothing in particular and is only used in AbstractFeature. This should make things reasonably simple when GPlates is looking for any PLATES fields.
• see http://www.gplates.org/trac/wiki/PlatesLineFormat for the full description.

• contains integer[1] regionNumber
  • 2-digit integer
• contains integer[1] referenceNumber
  • 2-digit integer
• contains integer[1] stringNumber
  • 4-digit integer
• contains string[1] geographicDescription
  • ASCII string, no specified character length
• contains integer[1] plateIdNumber
  • 3-digit integer
• contains double[1] ageOfAppearance
  • 6 char, 1 d.p float number, in Ma
• contains double[1] ageOfDisappearance
  • 6 char, 1 d.p float number, in Ma
• contains string[1] dataTypeCode
  • ASCII string, 2 characters
• contains integer[1] dataTypeCodeNumber
  • 4-digit integer
• contains string[1] dataTypeCodeNumberAdditional
  • ASCII string, 1 character
• contains integer[1] conjugatePlateIdNumber
  • 3-digit integer
• contains integer[1] colourCode
  • 3-digit integer
• contains integer[1] numberOfPoints
  • 5-digit integer, number of points (not counting the final "terminator" point (99.0000,99.0000))

TimeDependentPropertyValue<T>

- Abstract parent of all structural types handling time-dependency for property values.

• contains const string[1] valueType
  • The stringified version of the template-like "T" parameter. The template parameter passed to a TimeDependentPropertyValue will be stringified and put in the valueType property, to record what type this TimeDependentPropertyValue will store.

ConstantValue<T>

- Most basic case of TimeDependentPropertyValue

• contains T[1] value
  • The ConstantValue time-dependent value needs to be very flexible regarding what it can hold. So we use "T" like a 'C++ template' or 'generic' type.
• contains string[0..1] description
  • Annotation property; as the other time-dependent-property terminator, ConstantValue deserves a description field as much as TimeSample does.

IrregularSampling<T>

- TimeDependentPropertyValue combining samples and an interpolation function

• contains TimeSample<T>[1..*] timeSample
  • The values and associated time instants that are to be used, and interpolated as necessary.
• contains InterpolationFunction[0..1] interpolationFunction
  • The method to use to interpolate between TimeSlices.

TimeSample<T>

- Single TimeInstant with an associated value.

• Used in IrregularSampling time dependent property values, e.g. SlerpInterpolation, to provide the data points to interpolate between.

• contains T[1] value
  • The TimeSample time-dependent value needs to be very flexible regarding what it can hold. So we use a 'C++ template' or 'generic' type, T.
• contains gml:TimeInstant[1] validTime
  • The time instant associated with this sample value.
• contains string[0..1] description
  • Annotation property; this will be most useful to annotate the IrregularSampling of FiniteRotations used in TotalReconstructionSequence, mirroring comments commonly found in PLATES rotation files.
• contains const string[1] valueType
  • The stringified version of the template-like "T" parameter. The template parameter passed to a TimeSample will be stringified and put in the valueType property, to record what type this TimeDependentPropertyValue will store.
• contains boolean[0..1] isDisabled
  • in PLATES rotation files, a common technique is to use a moving plate ID of 999 to "comment out" a line (a single total reconstruction pole within the total reconstruction sequence)
  • However, it *should still remain within the sequence* when the sequence is loaded, it should just be disabled/deactivated/whatever. This boolean allows for this behaviour.

PiecewiseAggregation<T>

- TimeDependentPropertyValue combining several different types of TimeDependentPropertyValue joined by time windows

• contains TimeWindow<T>[0..*] timeWindow
  • These TimeWindows will contain a TimePeriod, plus another TimeDependentPropertyValue - this way we can join several different methods of time-dependency together, such as a ConstantValue followed by a IrregularSampling followed by another ConstantValue.

TimeWindow<T>

- Single TimePeriod with an associated time-dependent property value.

• Used in PiecewiseAggregation time dependent property values to join different methods of time-dependency together with TimeWindows.

• contains TimeDependentPropertyValue<T>[1] timeDependentPropertyValue
  • The TimeSample time-dependent value needs to be very flexible regarding what it can hold. So we use a 'C++ template' or 'generic' type, T.
• contains gml:TimePeriod[1] validTime
• contains const string[1] valueType
  • The stringified version of the template-like "T" parameter. The template parameter passed to a TimeWindow will be stringified and put in the valueType property, to record what type this TimeDependentPropertyValue will store.

InterpolationFunction

- Abstract parent for various interpolation methods

• used in IrregularSampling to interpolate between TimeSlices.

FiniteRotationSlerp

- Spherical Linear Interpolation function

• This is an interpolation function designed to interpolate between FiniteRotations.
• Referring to it as an empty standalone xml element, instead of some predefined text string, has the advantage that we can add parameters to it later if necessary.
• This will appear in the XML as a simple <gpml:FiniteRotationSlerp /> element, to indicate the type of interpolation desired in the IrregularSampling TimeDependentPropertyValue.

InstantaneousClosedPlateBoundary

- Snapshot closed polygon plate boundary that is pre-reconstructed to a specific instant in time.

• The "Instantaneous" view of a PlateSlab's closed boundary at an instant in time. It is only valid for a specific time, not reconstructable, and the geometry of this boundary is a simple polygon. The coordinates used are paleo-coordinates. Instantaneous features are designed for export to programs that are not able to reconstruct features themselves. This InstantaneousClosedPlateBoundary would most likely have been derived from a ClosedPlateBoundary.

• contains gml:Polygon[1] boundary
  • An instantaneous snapshot of the plate boundary, represented as a polygon using paleo-coordinates.

ClosedPlateBoundary

- Rigid closed polygon plate boundary that can be reconstructed to any time.

• a simple geometric view of a PlateSlab's closed boundary, possibly derived from a TopologicalClosedPlateBoundary. It is reconstructable, and so the polygon is encoded using present-day coordinates. This type of plate boundary might be most useful as a "Grid Mask" for gridded data relating to the plate.
• Some standard properties are very useful for a ClosedPlateBoundary. The .reconstructionPlateId property inherited from ReconstructableFeature will allow us to associate one (or more, potentially) gpml:plateId s with the plate boundary, gml:name can be used to name the plate, and validTime indicates the lifetime of this plate polygon.

• contains TimeDependentPropertyValue<gml:Polygon>[1] boundary
  • A stand-alone, reconstructable image of the plate boundary, represented as a polygon using present-day-coordinates.

InstantaneousClosedContinentalBoundary

- Snapshot closed polygon continental crust boundary that is pre-reconstructed to a specific instant in time.

• Similar (but not identical) to InstantaneousClosedPlateBoundary, but for crust type differences (oceanic-continental). It is only valid for a specific time, not reconstructable, and the geometry of this boundary is represented in paleo-coordinates.
• See also: ClosedContinentalBoundary, TopologicalClosedContinentalBoundary, and PassiveContinentalBoundary.

• contains enumeration ContinentalBoundaryCrustEnumeration[0..1] type
  • type of the crust contained within this boundary: enumeration.
  • = "Continental" : the interior of this boundary is a region of continental crust.
  • = "Oceanic" : the interior of this boundary is a region of oceanic crust.
  • = "Unknown" : the value of this property is officially unknown; there is no information about which type of crust this boundary is defining.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which side of the boundary is continental crust and which is oceanic, only that the boundary exists. The property is unspecified or indeterminate.
• contains enumeration ContinentalBoundaryEdgeEnumeration[0..1] edge
  • .edge is an enumeration:
  • = "InnerContinentalBoundary" : This Closed Continental Boundary defines the Inner edge of the continental boundary (closest to centre of continental crust - note that in the less common case of defining a closed boundary of type=oceanic crust, the "Inner" enumeration still refers to the innermost edge of -Continental- crust.)
  • = "OuterContinentalBoundary" : This Closed Continental Boundary defines the Outer edge of the continental boundary (furthest away from centre of continental crust, closest to oceanic crust - note that in the less common case of defining a closed boundary of type=oceanic crust, the "Outer" enumeration still refers to the outermost edge of -Continental- crust.)
  • = "Unknown" : This Closed Continental Boundary was digitised or imported without any data telling us how the boundary was chosen with regard to inner and outer edges of the continental crust. The value of this property is officially unknown.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which edge of the boundary polygon is represented by this line. The property is unspecified or indeterminate.
• contains gml:Polygon[1] boundary
  • an instantaneous snapshot of the crust boundary, represented as a polygon using paleo-coordinates.

ClosedContinentalBoundary

- Rigid closed polygon continental crust boundary that can be reconstructed to any time.

• Similar (but not identical) to ClosedPlateBoundary, but for crust type differences (oceanic-continental). It can be rotated via the usual reconstruction mechanisms, and the geometry of this boundary is represented in present-day-coordinates.
• See also: InstantaneousClosedContinentalBoundary, TopologicalClosedContinentalBoundary, and PassiveContinentalBoundary.

• contains enumeration ContinentalBoundaryCrustEnumeration[0..1] type
  • type of the crust contained within this boundary: enumeration.
  • = "Continental" : the interior of this boundary is a region of continental crust.
  • = "Oceanic" : the interior of this boundary is a region of oceanic crust.
  • = "Unknown" : the value of this property is officially unknown; there is no information about which type of crust this boundary is defining.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which side of the boundary is continental crust and which is oceanic, only that the boundary exists. The property is unspecified or indeterminate.
• contains enumeration ContinentalBoundaryEdgeEnumeration[0..1] edge
  • .edge is an enumeration:
  • = "InnerContinentalBoundary" : This Closed Continental Boundary defines the Inner edge of the continental boundary (closest to centre of continental crust - note that in the less common case of defining a closed boundary of type=oceanic crust, the "Inner" enumeration still refers to the innermost edge of the -Continental- crust.)
  • = "OuterContinentalBoundary" : This Closed Continental Boundary defines the Outer edge of the continental boundary (furthest away from centre of continental crust, closest to oceanic crust - note that in the less common case of defining a closed boundary of type=oceanic crust, the "Outer" enumeration still refers to the outermost edge of the -Continental- crust.)
  • = "Unknown" : This Closed Continental Boundary was digitised or imported without any data telling us how the boundary was chosen with regard to inner and outer edges of the continental crust. The value of this property is officially unknown.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which edge of the boundary polygon is represented by this line. The property is unspecified or indeterminate.
• contains TimeDependentPropertyValue<gml:Polygon>[1] boundary
  • a stand-alone, reconstructable snapshot of the plate boundary, represented as a polygon using present-day-coordinates.

InferredPaleoBoundary

- Part of a plate boundary defined by hand for real-world geology that no longer exists.

• e.g. the InferredPaleoBoundary between India and Asia that has since been subducted under the Himalaya.
• An 'Instantaneous' copy of this class exists, InstantaneousInferredPaleoBoundary.

• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] unclassifiedGeometry
  • All geometry defined for the feature where the purpose is not given or unclear.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] centerLineOf
  • The inferred boundary. This is the default location for imported geometry.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] errorBounds
  • An optional error boundary for the feature. Note that we can use LineStrings or Polygons or a combination of both - anything substitutable for gml:_Geometry.

gml:AbstractCoverage

• This class is external to the GPGIM; it belongs to the GML schemas, and is included here only for reference.
• Listed below are the general descriptions of the properties that will be most useful to us. They do not represent GML's abstract coverage element with perfect accuracy.

• contains external gml:_Geometry[1] gml:domainSet
  • Any GML Geometry might be found here, but the most common case will be gml:MultiPoint geometry (InstantaneousVelocityField).
• contains external gml:RangeSetType[1] gml:rangeSet
  • The value of this property can be one of gml:DataBlock, gml:File, some number of gml:ValueArray or gml:_ScalarValueList. For the time being, we are only concerning ourselves with the gml:DataBlock encoding.
• contains external gml:CoverageFunctionType[0..1] gml:coverageFunction
  • The value of this property can be one of gml:MappingRule or gml:GridFunction, but it is an optional property. A linear mapping is assumed.

InstantaneousCoverage

• While our coverage features such as InstantaneousVelocityField would clearly fit in the category of "Instantaneous" GPML features (Not reconstructed; only defined at a single moment in time), it is also a GML Coverage. This means that it must derive (directly or indirectly) from gml:AbstractCoverageType in the GML Application Schema, and we cannot have it derive from our custom InstantaneousFeature abstract base.
• Nevertheless, we can include all the properties that InstantaneousFeature would normally grant - the choice of parent XML element / content model has no visible effect on the final structure of InstantaneousVelocityField in documents.
• InstantaneousVelocityField will still have the gml:domainSet and gml:rangeSet properties, and it can still have the gpml:reconstructedTime and gpml:reconstructedPlateId properties. The requirement of setting the parent content model to gml:AbstractCoverageType is probably just to support some theoretical GML-aware application that can analyse the XML schema and figure out that this InstantaneousVelocityField is a Coverage - GPlates will not need such information, as it can figure out the capabilities of the feature based on what properties are supplied ('Duck Typing').
• The best solution to this problem is to create this InstantaneousCoverage abstract base, which will include the GML Coverage properties via gml:AbstractCoverageType and also duplicate the standard "Instantaneous" properties which we would normally get via InstantaneousFeature.
• GmlBook p244 "All Coverages [content models] must derive, directly or indirectly, from AbstractCoverageType."

• contains FeatureSnapshotReference<TimeVariantFeature>[0..1] derivedFrom
  • an optional link to the ReconstructableFeature this Instantaneous snapshot was taken from, for historical interest.
  • Note that most Coverages will not need this property, as they will be calculated on the fly from other data and not just be a snapshot of a ReconstructableCoverage.
• contains gml:TimeInstant[0..1] reconstructedTime
  • the TimeInstant corresponding to the moment this InstantaneousFeature was converted from its Reconstructable original.
  • Normal GPlates Features store their geometry in present-day coordinates, and store reconstruction information to rotate them into paleo-coordinates. However, for exporting data into other GPML aware programs, i.e. GMT, it is necessary to do the rotations on behalf of the external application. The .reconstructedTime property of the Instantaneous feature records what time this Feature was reconstructed to by GPlates, (in Ma or whatever 'uom' and 'frame' you want in the TimePeriod).
  • Note that some Coverages e.g. InstantaneousVelocityField may want to use this property to record what time instant the velocities were calculated at. In this case, it is not simply a copy of some original gpml:validTime property, as there was no ReconstructableCoverage involved in the first place.
• contains gml:TimePeriod[0..1] validTime
  • Instantaneous features only really exist for a single instant, the TimeInstant in the reconstructedTime property, set when a snapshot is made of a ReconstructableFeature. The 'TimePeriod validTime' property of the ReconstructableFeature is no longer applicable.
  • However, the original information about the features' lifespan is still useful information. Isochrons in particular measure their age as their time-of-appearance. This information would be lost in InstantaneousIsochron snapshots unless the information is copied to this .validTime property.
  • This property may at first glance appear to be identical to TimeVariantFeature.validTime, and it is true that the value of this property should be the same; however it serves a different purpose (useful record of original data) and is in fact an entirely different .validTime property with a TimePeriod value.
  • Note that most Coverages will not need this property, as they will be calculated on the fly from other data and not just be a snapshot of a ReconstructableCoverage.
• contains gpml:plateId[0..1] reconstructedPlateId
  • in the spirit of not throwing away information, the plateId at time of conversion to an InstantaneousFeature type is recorded here. Unlike ReconstructableFeature.reconstructionPlateId, this is not a time-dependent property, and will only ever refer to one gpml:plateId.
  • Note that some Coverages e.g. InstantaneousVelocityField may want to use this property to record an associated plate id such as the plate that the velocities are valid for. In this case, it is not simply a copy of some original gpml:reconstructionPlateId property, as there was no ReconstructableCoverage involved in the first place.

InstantaneousVelocityField

- A point-sampled velocity field, suitable to represent the motion of plates and provide kinematic surface constraints for geodynamic simulation software such as CitComS.

• The purpose of the InstantaneousVelocityField is to encapsulate point-velocity fields for export into other software. Motion of a particular plate can be exported as a number of 'snapshots' of InstantaneousVelocityFields, and then imported into CitcomS or UnderworldS to constrain a mantle convection model by supplying the conditions which must be satisfied on the surface.
• The velocity field is represented using a GML Coverage. There are two important properties for coverages: the gml:domainSet and gml:rangeSet. The domain of a Coverage specifies the geographical location - in this case, the velocity sample-points. The range describes what additional data should be associated with each point - in this case, a velocity expressed as colat/lon.
• gml:domainSet property: Any GML Geometry might be found here in coverages, but for velocity fields, we want gml:MultiPoint geometry.
• gml:rangeSet property: GML Coverages allow for one of gml:DataBlock, gml:File, or some number of gml:ValueArray or gml:_ScalarValueList for this property. For velocity fields, we are only concerning ourselves with the gml:DataBlock encoding, with VelocityColat and VelocityLon values for each data point.
• gpml:reconstructedTime property: this may be a useful place to store the instant that this snapshot was made at, as useful metadata that importers of this Feature might be interested in. It is not mandatory.
• gpml:reconstructedPlateId property: this may be a useful place to store the plate ID that these velocities apply to, as useful metadata that importers of this Feature might be interested in. It is not mandatory.
• For an example, see http://www.earthbyte.org/Resources/GPGIM/examples/velocity_colat_lon_example.gpml

gml:DataBlock

- GML DataBlock for encoding range sets as compact sequences of tuples.

• This class is external to the GPGIM; it belongs to the GML schemas, and is included here only for reference.
• Listed below are the general descriptions of the properties that will be most useful to us. They do not represent GML's data block element with perfect accuracy.
• For more details on GML's DataBlock encoding, see The GML Book p252.

• contains external gml:CompositeValue[1] gml:rangeParameters
  • The gml:rangeParameters property is used to define the different fields that make up each entry in the DataBlock.
  • For example, a gpml:InstantaneousVelocityField will have a gml:DataBlock as its gml:rangeSet. The DataBlock will have two gml:valueComponent entries for the gml:CompositeValue used in this property: a gpml:VelocityColat and a gpml:VelocityLon. Each data point will then have a colat and lon velocity component associated with it.
• contains external string[1] gml:tupleList
  • A space-separated list of tuples. There will be one entry per point of data (as supplied by the gml:rangeSet property in whichever Feature uses this gml:DataBlock).
  • Tuples are a comma-separated list of values, each corresponding to a variable defined in the gml:rangeParameters property. For example, the colat and lon velocity components of a gpml:InstantaneousVelocityField.

gml:CompositeValue

- GML XML Schema element for including multiple value objects in-line.

• This class is external to the GPGIM; it belongs to the GML schemas, and is included here only for reference.
• The GML schemas use gml:CompositeValue as a way to include one or more GML Value Objects. This allows application schemas (such as GPML) to define their own measure types which can be used wherever a GML Value Object or Composite Value is expected.
• Application-defined value objects must be substitutable for gml:_Value. GPML defines two such value objects useful for InstantaneousVelocityField coverages: VelocityColat and VelocityLon.

VelocityColat

• attribute string gml:uom

• VelocityColat and VelocityLon are defined as GML Value Objects. These value objects are used by GPML in gml:DataBlock encodings to define range parameters (for coverages such as InstantaneousVelocityField).
• They are defined as being substitutable for gml:_Value, and can be found within a gml:CompositeValue element.
• When used in a gml:DataBlock encoding, these elements represent 'template' parameters that determine the mapping of values within the gml:DataBlock's tupleList property. The actual value specified in the <gpml:VelocityColat> element inside GPML documents is the keyword 'template'. For more verbose encodings that do not use gml:DataBlock, this will be an in-line literal value.
• The standard 'gml:uom' attribute can be applied to VelocityColat. The most appropriate value is "urn:x-si:v1999:uom:cm_per_year" for point-velocity fields.
• For examples of using value objects in this manner, see the GmlBook p260.
• We define this by hand in the GML schemas, as an xs:element which is substitutable for gml:_Value.

VelocityLon

• attribute string gml:uom

• VelocityColat and VelocityLon are defined as GML Value Objects. These value objects are used by GPML in gml:DataBlock encodings to define range parameters (for coverages such as InstantaneousVelocityField).
• They are defined as being substitutable for gml:_Value, and can be found within a gml:CompositeValue element.
• When used in a gml:DataBlock encoding, these elements represent 'template' parameters that determine the mapping of values within the gml:DataBlock's tupleList property. The actual value specified in the <gpml:VelocityColat> element inside GPML documents is the keyword 'template'. For more verbose encodings that do not use gml:DataBlock, this will be an in-line literal value.
• The standard 'gml:uom' attribute can be applied to VelocityLon. The most appropriate value is "urn:x-si:v1999:uom:cm_per_year" for point-velocity fields.
• For examples of using value objects in this manner, see the GmlBook p260.
• We define this by hand in the GML schemas, as an xs:element which is substitutable for gml:_Value.

Contour

- Polyline and/or polygon geometry with additional z-value semantics.

• When a specific depth/height/z-value is associated with this geometry via the 'level' property, it can be called a Contour. Otherwise the term 'Extent' is more suitable, but the two share many properties.
• Contours can also have information about the origin of their geometry:
• The most common use for this class will be Bathymetric Contours. These are 'picked' from a Bathymetry grid, and are conours because they follow a particular depth, for example, the "2000m" contour.
• When the 'level' property is omitted, this geometric type can be used for defining the extents of features based on some gridded data, such as a Gravity map, but without implying that all points of the extent share the same elevation.
• There are some standard, commonly used types of Contour, such as Bathymetry or Topography. However, practically any field or gridded data might be used to create contours.
• For example, picking the extent of an extinct IslandArc might be done from looking at a Gravity grid and choosing the outline by hand. There is no specific criteria used, unlike when defining a Contour.

• contains string[0..*] subcategory
  • As this class derives from gml:AbstractGeometryType in order to be substitutable for gml:_Geometry, it cannot inherit the standard gpml:subcategory property. As it is highly useful for contour types, it is defined directly.
  • Suggested Subcategories:
  • = "Bathymetry" : A contour measuring depth of the ocean floor beneath sea level.
  • = "Topography" : A contour measuring height of land above sea level.
  • = "Gravity" : chosen from a Gravity grid.
  • = "Magnetic" : chosen from a Magnetic grid.
• contains string[0..1] description
  • 'description' is for specific notes relating to this particular Contour.
  • since Contour is neither a gpml:Feature nor a gml:Feature, we need to explicitly include support for a free-form text description field.
• contains gml:_Geometry[0..1] outlineOf
  • The geometry of the Contour specifying a closed or partial outline - expected to potentially use gml:MultiGeometry, gml:LineString and gml:Polygon.
  • As this is a geometry type, it makes little sense to define "This is the default location of imported geometry"; this -is- geometry, any importing or default semantics is left up to the parent gpml:Feature.
  • Note on Time-Dependency: Contours will themselves be wrapped up in TimeDependentPropertyValue as appropriate for the containing gpml:Feature's property.
• contains gpml:measure[0..1] level
  • The value or criteria or level that the contour was chosen for. For marine science, which mostly deals with Bathymetric contours, this criteria would be depth : for instance, a depth of 2000m. Above sea level, this would be a Topographic contour, which might still measure the contour level in metres but measures the height as opposed to the depth. It is even conceivable that someone may want to pick out a "Gravity" contour from a gravity grid; the 'level' of the contour might now be measured in mGals, and words like 'height' and 'depth' have little meaning. Hence the rather general name of this property.
  • When this property is absent, it implies missing data for a Contour, or a Contour chosen with no regard to following a specific level (an "Extent")
  • Then why not give it a more abstract name? Because 'Contour' has special meaning to geoscientists and is a favourite 'go-to' word.

AbstractField

- Abstract superclass for various field data, including stand-alone Contours and outlines.

• Assorted contour-like data and (in future releases) gridded data share AbstractField as a parent class.
• Types of contour (and later, gridded) data include: Bathymetry, Topography, Gravimetry, Magnetics, GlobalElevation, OceanicAge, CrustalThickness, DynamicTopography, MantleDensity, HeatFlow, SedimentThickness, Roughness, SpreadingRate, SpreadingAsymmetry, Stress
• This is because all contoured data is picked from a gridded source, and similarly with most stand-alone outline data. In addition, there are many, many types of gridded data that we may wish to use in the future. With most of these types, it still makes sense to be able to pick outlines and contours from the grid - they are useful in many cases.
• The following list derived from some of the actual data files on Maria's filesystem.
• An 'Instantaneous' copy of this class exists, InstantaneousAbstractField.

• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] outlineOf
  • Geometry specifying a closed or partial outline - expected to potentially use gml:MultiGeometry along with gpml:Contour (which will in turn use more gml:_Geometry - gml:LineString and gml:Polygon in particular). This is the default location for imported geometry.
  • Time-dependent, because although rotatable shifting deforming contours through time sounds like a mouthful, Simula has an interest in this and we should leave the door open.

Bathymetry

- Sea floor depth data, including bathymetric contours and grids.

• Usually measured in m (depth)
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousBathymetry.

Topography

- Elevation data, including topographic contours and grids.

• Usually measured in m (height)
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousTopography.

Gravimetry

- Gravity grids, outlines, and contours.

• Usually measured in mGal
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousGravimetry.

Magnetics

- Magnetic field feature for grid data and contours.

• Usually measured in mT
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousMagnetics.

GlobalElevation

- Merged bathymetric and topographic elevation data

• Though it is probably a good idea to keep Bathymetry and Topography seperate due to their differences, there are plenty of instances of merged data sets combining ocean depth with land height fields. This Feature supports those cases.
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousGlobalElevation.

OceanicAge

- Age of seafloor, for contours and grids.

• While oceanic age is most frequently represented with grids, it is still useful to pick out contours of specific ages.
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousOceanicAge.

CrustalThickness

- Crustal thickness data, typically represented using grids, related to Isopach data.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousCrustalThickness.

DynamicTopography

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• Seismic Tomography (MantleDensity) is used as a source of data to create DynamicTopography.
• An 'Instantaneous' copy of this class exists, InstantaneousDynamicTopography.

MantleDensity

- Density of the mantle, computed using Seismic Tomography.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• MantleDensity data can be applied to the creation of DynamicTopography grids.
• An 'Instantaneous' copy of this class exists, InstantaneousMantleDensity.

HeatFlow

- Oceanic heat-flow data

• Heat flow is typically measured by placing devices on the ocean floor to measure temperature. For example, heat will emanate from a MidOceanRidge.
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousHeatFlow.

SedimentThickness

- Isopach data indicating sediment thickness using grids and/or contours.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• e.g. http://www.usawaterquality.org/conferences/2005/Posters/Negrini.pdf
• An 'Instantaneous' copy of this class exists, InstantaneousSedimentThickness.

Roughness

- Roughness data computed from Gravity grids.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• This feature is an example of one which would use gridded data almost exclusively, with little need for Contours and outlines. However, in any case of gridded data, there is the possibility that such contours may be desirable, and should be available as an option.
• An 'Instantaneous' copy of this class exists, InstantaneousRoughness.

SpreadingRate

- Sea-floor spreading rate.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousSpreadingRate.

SpreadingAsymmetry

- Asymmetry in sea-floor spreading rate.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousSpreadingAsymmetry.

Stress

- Stress grids and contour data.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousStress.

TectonicSection

- Superclass to group ridgelike and related tectonic features together.

• Plate-tectonic features that can form boundaries between plates fall under this class.
• An 'Instantaneous' copy of this class exists, InstantaneousTectonicSection.

• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] unclassifiedGeometry
  • All geometry defined for the feature where the purpose is not given or unclear.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] centerLineOf
  • The central line defining the tectonic feature, generally using gml:LineString, with the possibility of gml:MultiGeometry or gml:MultiCurve. This is the default location for imported geometry.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] outlineOf
  • Geometry specifying a closed or partial outline - expected to potentially use gml:MultiGeometry, gml:LineString and gml:Polygon. This may include Contours (or extents) associated with this tectonic section.
• contains gpml:plateId[0..1] leftPlate
  • Annotation property describing the plates on the "left" side of this tectonic section. Not to be used for reconstruction purposes, as these properties would be an imprecise representation of the crust on each side in many cases. Primarily of interest to the MidOceanRidge feature, where it is used for the purpose of a richer description.
  • Not a time-dependent property because, for MidOceanRidge at any rate, that's insanity. A MidOceanRidge -generates- crust. For other boundary features, like SubductionZone, this property is only really used as annotation, (i.e. "this SZ is mostly consuming plate 541") and doesn't need to be over-complex.
  • This property doesn't support multiple plateIds per side for similar reasons to the ones above; in the case of MidOceanRidge, the usefuless of this property hinges on the potential to e.g. interpolate between both sides of the MOR and determine velocity. If more than one plateId per side were supported, topology would have to be taken into consideration, and pieces would have to move at different rates - and so the MOR would have to be broken up into segments, PLATES style. Perhaps when we get segmented MORs in the next release GPGIM, we can consider these extra possibilities. Until then, there's really no point in making this more complex than it needs to be.
• contains gpml:plateId[0..1] rightPlate
  • Annotation property describing the plates on the "left" side of this tectonic section. Not to be used for reconstruction purposes, as these properties would be an imprecise representation of the crust on each side in many cases. Primarily of interest to the MidOceanRidge feature, where it is used for the purpose of a richer description.
  • Not a time-dependent property because, for MidOceanRidge at any rate, that's insanity. A MidOceanRidge -generates- crust. For other boundary features, like SubductionZone, this property is only really used as annotation, (i.e. "this SZ is mostly consuming plate 541") and doesn't need to be over-complex.
  • This property doesn't support multiple plateIds per side for similar reasons to the ones above; in the case of MidOceanRidge, the usefuless of this property hinges on the potential to e.g. interpolate between both sides of the MOR and determine velocity. If more than one plateId per side were supported, topology would have to be taken into consideration, and pieces would have to move at different rates - and so the MOR would have to be broken up into segments, PLATES style. Perhaps when we get segmented MORs in the next release GPGIM, we can consider these extra possibilities. Until then, there's really no point in making this more complex than it needs to be.
• contains gpml:plateId[0..*] conjugatePlateId
  • A reference to the plate Id (general-purpose plate Id or specific plate Id for motion of a cluster of Features) that has the 'pair' or 'twin' of this thing. See Isochron. This property is intended to support transition from PLATES style information to the feature-centric GPlates model.

MidOceanRidge

Mid-Ocean Ridge - A spreading rift on oceanic crust

• The MidOceanRidge class needs to be pretty flexible. In the PLATES methodology, MOR lines are typically used to represent both the 'spreading' and 'transform' sections of the ridge - and so a lot of older data sets will have rigid MidOceanRidges once they are imported. Ideally, they would use an explicit Transform to join up MidOceanRidge and SubductionZone pieces.
• The other area that MidOceanRidge needs to encompass is those ridges that have become an "Extinct Ridge" through a process of ridge propagation. This is handled via the .isActive time-dependent property below.
• It is possible that later releases of the GPGIM will support a single MidOceanRidge Feature with heterogenous 'segments'.
• An 'Instantaneous' copy of this class exists, InstantaneousMidOceanRidge.

• contains TimeDependentPropertyValue<boolean>[0..1] isActive
  • 'true' while this MidOceanRidge is still active, 'false' if it has since become an "Extinct Ridge" due to ridge propagation in the area. Optional - if not present for a given time period, it is safe to assume the ridge is still actively generating crust.
  • Due to ridge jump / propagation, and various plate-tec forces in the region, a midoceanridge-transformfault-midoceanridge area may start ignoring the extra midoceanridge and transform, and instead start 'propagating' one ridge to take over the job of the other.
  • An "Extinct Ridge" is a MidOceanRidge that has 'died' by this process, and no longer creates oceanic crust.
  • #Time-Dependency: This property can be time-dependent - in most data, it would likely be a simple ConstantValue<boolean>, but if the user wishes to model the activity over time, the data could use PiecewiseAggregation<boolean>, supporting separate TimeWindows to describe the active period and inactive period of this MidOceanRidge.

ContinentalRift

Continental Rift - A spreading rift on continental crust

• Functionally, this behaves similarly to MidOceanRidge, but a ContinentalRift is defined for continental crust only.
• An 'Instantaneous' copy of this class exists, InstantaneousContinentalRift.

SubductionZone

- A zone of descending lithospheric plate

• The standard model of a subduction zone is a linear tectonic region which consumes plate material on one side, while being largely 'attached' to a plate on the other side. Similarly to MidOceanRidge, the leftPlate and rightPlate properties are often set to advise approximately which plate is being consumed. The SubductionZone is always 'attached' to the overriding plate, as far as the gpml:plateIds are concerned.
• Not necessarily a 'Zone', could be a linelike feature or have an additional polygon geometry.. The gml property .centerLineOf is used to indicate where the subducting plate meets the overriding plate.
• An 'Instantaneous' copy of this class exists, InstantaneousSubductionZone.

• contains enumeration TimeDependentPropertyValue<SubductionSideEnumeration>[0..1] subductingSlab
  • Indicates the side of the line that the subducting slab is on. The overriding plate will be on the opposite side.
  • .subductingSlab is an enumeration: Assuming there is a suitable centerLineOf supplied, and understanding that the order of points in the line matters, we can establish a "left" side and a "right" side to the .centerLineOf. this property indicates which of those "left" and "right" sides the subducting slab is on. The overriding plate will be on the opposite side.
  • = "Left" : The subducting slab is on the left of this SubductionZone, according to the directed gml:LineString .centerLineOf
  • = "Right" : The subducting slab is on the right of this SubductionZone, according to the directed gml:LineString .centerLineOf
  • = "Unknown" : the value of this property is officially unknown; there is no information about which side of the SubductionZone is which.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which side the subducting slab is on. The property is unspecified or indeterminate.
  • #Time-Dependency: Most common use-case would be a ConstantValue<enumeration>, but there is the --possibility-- that a single SubductionZone may change polarity, and that someone may want to model that in GPML, in which case the data would be a PiecewiseAggregation<enumeration>
• contains FeatureReference<IslandArc>[0..*] islandArc
  • Since there could be multiple small island arcs that are part of a large subduction zone, we will let the subduction zone keep track of its associated IslandArc(s), if any.