Points of Interest Core

Terminology

The term points of interest is used in a broad sense in this specification to refer to a loosely coupled and inter-related set of terms: locations, POIs and places.

This section is primarily based on the wiki home page definition of POI.

Location: The term location is used to refer to a geographical construct, a physically fixed point, typically on the surface of the Earth (relative to WGS-84), though locations can be relative to another coordinate system. Locations can be a single point, a centroid, a minimum bounding rectangle, or a set of vectors. A location should be persistent over time and does not change.
Points of Interest: Unlike the term location, the term POI is a human construct. POIs describe information about locations such as name, category, unique identifier, or civic address.
Places: A place is also a human construct which typically has a coarse level of spatial granularity. Places are generally larger scale administrative constructs, either informally or formally defined. Countries, states, counties, districts, neighborhoods and postal codes or telephone area codes are all places. Places are also informally or colloquially defined, such as the Home Counties in the United Kingdom and the Bay Area in the United States.; Places have spatial relationships; with parents, children, adjacencies and contained by semantics. Places also have the same attribute set as POIs, although with differing interpretations based on scale; for example, the address of a Place or its URI would refer to the address of the administrative or governing body of the place.; A place typically contains multiple POIs and can also be coterminous with a POI. In the former case, a place, such as a city or a neighborhood, will contain multiple POIs. In the latter case, a place and a POI will occupy the same position and extent, such as in the case of Yellowstone National Park, which is both a Place and a POI.
Primitive: The term primitive refers to the basic components of a POI. For example, a POI could be a collection of location and category primitives.
Coordinate: The term coordinate refers to one of a sequence of n numbers designating the position of a point in n-dimensional space [[ISO19111]].
Coordinate Reference System: The term coordinate reference system refers to a coordinate system that is related to an object by a datum [[ISO19111]].
Coordinate System: The term coordinate system refers to a set of mathematical rules for specifying how coordinates are to be assigned to points [[ISO19111]].
Datum: The term datum refers to a parameter or set of parameters that define the position of the origin, the scale, and the orientation of a coordinate system [[ISO19111]].
Geolocation: The term geolocation refers to the identification of the real world geographic location of an object.
Point: The term point refers to a 0-dimensional geometric primitive, representing a position [[ISO19107]].
Position: The term position refers to a data type that describes a point or geometry potentially occupied by an object or person [[ISO19133]].
Route: The term route refers to a sequence of links and / or partial links that describe a path, usually between two positions, within a network [[ISO19133]].

POI Data Model

The following primitives can be combined to represent a POI.

Geo-reference

Geo-references are used a lot and were difficult to introduce just in the middle of the location primitive, so it got a promotion, even though it only appears in the location primitive.

A geo-reference is a reference to a location. A geo-reference can represent location in a variety of ways, such as the geospatial coordinates for the center of the POI, a civic address, an area (simple bounding box, or a polygon, or a 3d object), relative to a particular map or other geo-reference or undetermined. Geo-references are used in the location primitive.

A geo-reference is of one of the following types:

Center

The Center geo-reference locates the center point of the POI. This type is largely used for display purposes.

Contains

Name	Required	Details
Coordinates	required
System	optional	If not specified WGS 84 is assumed
Longitude	required
Latitude	required
Altitude	optional	Defines the height in meters above or below sea level

OGC has recommended the term geolocation instead of georeference:
Georeference – While geo-reference is a valid term, geo-reference typically indicates that a geometry or an image has coordinate reference system metadata. The suggested term is geolocation as this term is used extensively in other standards work, including the work of the W3C.

Navigation Point

A Navigation Point geo-reference is to a point that is the logical destination for routing. For example, this may be a reference to the entrance of parking lot POI.

Contains

Name	Required	Details
Coordinates	required

Address

Note:Support for addresses in the XML syntax has been dropped for the FPWD, but reminds here in the data model.

An Address geo-reference is a civic address, such as a mailing address or a street address.

Contains

Name	Required	Details
Country	required	ISO country code (ISO 3166-1 alpha-3 country code)
Language	required	xml:lang Language Code
Street	optional	Can contain a variable mix of house number prefix, suffix, street base name and or street type
Floor	optional	+/- number
Suite	optional
Region	optional	Repeating: can contain a variable mix of administrative regions, neighborhood, city, state, etc.
Postal-code	optional

This is our first reference to language tags, should we use ISO 3166-1 or BCP 47/IETF RFC 5646? It's been suggested to use xmllang, but do we need to specify this in the data model? Probably, as we do want interchangeability between formats.

Route

This section needs reworking. Within the XML syntax there's a notion of a list of points, as well as a point type that is reused. In the Wiki draft Routes and Areas both have point lists, we should extract the point list concept out so it can be shared.

Optional. Represents routes and traces.

Contains

Point: Required. Repeating for a directed linked list of points

Area

An Area geo-reference represents a line-bounded area. The area is described by an ordered list of coordinates, where the first and last are the same.

I changed this one a bit, instead of introducing Points, I just made it have Coordinates, and mention that it is an ordered list of them where the first and last are the same. I figure the ordering can occur however such things happen in desired syntax (XML could be as they appear in document order or with an 'order' attribute, JSON may represent it as an array,etc)

Contains

Name	Required	Details
Coordinates	required	An ordered list of Coordinates, minimum of three, first and last must be the same.

Object

The following paragraphs are adapted from Christine Perey's email. Parts of this are related to collections of POIs/objects and is thus also related to ISSUE-28. This section needs serious attention.

The Object primitive provides a rich and flexible description of an object, which decouples the description of an object from where it is located.

An Object MAY have one location at a (temporary-duration undefined) specific point in time but does not have one fixed point over time.

An Object of Interest can be a parent to other Objects each with its own description to allow for the representation of complex objects that are the aggregate of a collection of Objects (a car, boat, or airplane).

It should not be inferred that each of the elements within the object primitive are not spatially synonymous, but do refer to the same object.

Represents a 3D object, building, etc.

Contains

Name	Required	Details

Undetermined

An Undetermined geo-reference represents a location that as of yet is undetermined. This can be used to describe a Place prior to the final location being resolved.

There are no members for an Undetermined geo-reference.

Relative

I made relative a member of geo-reference rather than a sub-member of the map geo-reference, as it seems useful outside of the map scope

A Relative geo-reference is described in terms of distance from and bearing to another location.

Name	Required	Details
Relative-Location-Object	required	ID or location object (ID) this relative reference refers to
Distance-From	required
Bearing-To	required
Relative height	optional

Map

Map georeference type has been dropped from the FPWD until it is better understood.

Location

The location primitive provides a rich and flexible description of the location of a POI. A location is a required part of a POI.

Contains

Name	Required	Details
Identifier	required	A unique identifier for this location.
Geo-reference	required	A reference to the actual location

I didn't follow the definition of a location identifier, so details were removed

Relationship primitive

The relationship primitive establishes 1-to-1 or 1-to-many relationships between POIs.

A relationship may be one of the following:

contained-within: A POI which is entirely contained within another POI, e.g. a POI describing a store may state that it is contained within a shopping mall
contains: A POI which entirely contains another POI, e.g. a POI describing a mall may state that it contains POIs for each store that is within the mall
adjacent-to: A POI which is physically adjacent to another POI, e.g. a POI representing a store within a mall may state that it is next door to another POI which represents the store next door
...: Need more relationship types

Should the details of the various relationship types themselves be in this section? Assuming yes for now

contained-within

todo

contains

todo

adjacent-to

todo

string primitive

Dropped per our discussion at f2f

Label primitive

POIs may have zero or more label primitives which represent a human readable label.

At F2F2 we decided to rename the name primitive to "label", and to allow labels to be marked as primary for each language represented.

ID primitive

POI must have an "id" primitive. It unambiguously identifies a POI within a particular implementation.

At F2F2 we discussed using URI fragments as IDs, as in XML. Using XML Base we could build a full URI that could then be used to identify the entire POI.

Categorization primitive

POI MAY have a "categorization" primitive, with one or more category identifiers.

Todo

meta data primitive

Todo. We haven't decided how this would work, and why this wouldn't just be covered by our extensibility story. Please see: ISSUE-18.

Time primitive

POI MAY have one or more time primitives that represent an individual point in time, a span of time, or a recurring time or time span.

XML Syntax

Even more so than the rest of this document, this section is a straw man proposal, so please treat it as such!

This section describes an XML syntax to represent the data model.

XML Notation

The following data types are from XML Schema, Part 2: Datatypes [XMLSCHEMA11-2]. The meanings are provided here as a convenience, for more complete information refer to the XML Schema, Part 2: Datatypes Recommendation.

Notation	Meaning
boolean	has the ·value space· required to support the mathematical concept of binary-valued logic: {true, false}
decimal	a subset of the real numbers, which can be represented by decimal numerals
float	patterned after the IEEE single-precision 32-bit floating point type [IEEE 754-1985].
double	atterned after the IEEE double-precision 64-bit floating point type [IEEE 754-1985].
duration	represents a duration of time.
dateTime	may be viewed as objects with integer-valued year, month, day, hour and minute properties, a decimal-valued second property, and a boolean timezoned property. Each such object also has one decimal-valued method or computed property, timeOnTimeline, whose value is always a decimal number; the values are dimensioned in seconds, the integer 0 is 0001-01-01T00:00:00 and the value of timeOnTimeline for other dateTime values is computed using the Gregorian algorithm as modified for leap-seconds
time	represents an instant of time that recurs every day
date	consists of top-open intervals of exactly one day in length on the timelines of dateTime, beginning on the beginning moment of each day (in each timezone), i.e. '00:00:00', up to but not including '24:00:00' (which is identical with '00:00:00' of the next day)
gYearMonth	represents a specific gregorian month in a specific gregorian year.
gYear	represents a gregorian calendar year
gMonthDay	a gregorian date that recurs, specifically a day of the year such as the third of May
gDay	a gregorian day that recurs, specifically a day of the month such as the 5th of the month
gMonth	gregorian month that recurs every year
anyURI	represents a Uniform Resource Identifier Reference (URI). An anyURI value can be absolute or relative, and may have an optional fragment identifie

We need to figure out: xml id/xml:base, xml:lang, units of measurement

`<pois>` element

The root element for an POI in XML syntax is the pois element. The <pois> element MUST contain one or more <poi> elements.

Attributes

The <pois> element has TBD attributes.

We may not allow for collections of POIs, in which case there will be no pois element.

The pois element could have attributes such as xml:lang and an id, but is there a case for more? What's the right way to represent text-wise that lang and id's can be on all elements?

`<poi>` element

The <poi> element encompasses all information about a single POI. The <poi> element MUST contain one or more <location> elements, and MAY contain one or more <label> and <category> elements.

Attributes

see above note in the <pois> element about lang and id

Representing coordinates

Many of the elements described below rely on a coordinates as attributes. In the interest of not repeating the definition, the following attributes are inferred whenever the coordinate attributes are referenced below.

Attributes

Name	Required	Type	Default value	Details
srsname	optional	anyURI	urn:ogc:def:crs:EPSG:6.6:4326	A URN as defined in OGC Definition identifier URNs in OGC namespace [OGC-07-092r1] of the geodetic system to which the latitude and longitude and altitude are relative
longitude	required	number	None
latitude	required	number	None
altitude	optional	number	?? sea level relative to system?

Is there an official geode tagging scheme, e.g. "wgs84", or "etrs89"? Apparently yes: http://portal.opengeospatial.org/files/?artifact_id=24045
Now tracked as issue: ISSUE-21.
How does this effect the altitude attribute?

`<point>` element

The <point> element is used in many different geo-reference types below. It represents a single set of coordinates, and can be ordered relative to other <point> elements within the parent element via the order attribute.

The <point> element has no character data.

Attributes

The <point> element uses the coordinate attributes, and an order attribute.

Name	Required	Type	Default value	Details
order	optional	unsigned-number	None	Applies only when a list of points is needed. Within the parent element containing the point list, there must be one `<point>` with the order attribute set to '0', other `<point>` element's order attribute MUST be unique and contiguous integers. Each point element within a point list MUST have the `order` attribute set.

Do we want to use an order attribute? Document order? A single attribute with a list of comma separated coordinates?
Now tracked as: ISSUE-19: how should we represent points? and a related issue: ISSUE-36: do we want to rely on document order?.

`<location>` element

The <location> element contains one or more geo-references elements (see below), and has no attributes or character data.

Geo-reference elements

The following elements are the XML mapping for the geo-references outlined in the data model. Geo-references are used only with in the <location> element.

`<center>` element

The <center> element has no character data, and only the coordinate attributes.

`<address>` element

Representing addresses is a tricky business, see Geolocation WG and IETF geopriv.
As such address will be moved to TBD in this draft. This issue is now tracked as ISSUE-40

Should there be a way to assign languages to addresses or parts of addresses?

`<navigation-point>` element

The <navigation-point> element has no character data and only the coordinate attributes.

`<area>` element

The <area> element MUST contain three or more <point> elements. The first and last points in an area point list must have the same latitude, longitude and altitude. The area element has no attributes.

`<object>` element

This geo-reference hasn't been written yet

Attributes

Name	Required	Type	Default value

`<undetermined>` element

The <undetermined> element has no character data and no attributes.

`<relative>` element

The <relative> element has no character data.

Attributes

Name	Required	Type	Default value	Details
location-id	required	idref (not really, more of a xsd:anyURI as it can be external too)	None	The fragment identifier or URI of the object to which this location is relative.
distance-from	required	integer	None	The distance this object is from the object referred to in the location-id attribute
bearing-to	required	decimal	None	?? radians? degrees?
relative-height	optional	integer	None

`<map>` element

Map georeference type has been dropped from the FPWD until it is better understood, so the map element has been dropped as well.

`<relationship>` element

The <relationship> element contains no character data.

Attributes

Name	Required	Type	Default value	Details
type	required	string	None	MUST be one of: "contained-within","adjacent-to", or "contains"
relative-to	required	URI	None

`<label>` element

Todo. At the f2f we agreed it would be label instead of name, and that multiples can exist, and one per language can be marked as primary

id representation

At F2F2 we discussed using URI fragments as IDs, as in XML. Using XML Base we could build a full URI that could then be used to identify the entire POI.

`<category>` element

The <category> element is a child of the <poi> element. It is used to identify a category scheme and a category within that scheme, as well as one or more labels for the category.

The <category> element MUST contain one or more <label> elements, and zero or more <association> elements.

See ISSUE-24.
I adjusted the Atom category element, to support multiple human readable labels via label sub elements and I try to give some meaning to the term attribute when there is no scheme.

Attributes

Name	Required	Type	Default value	Details
scheme	optional	URI	None	URI that identifies the categorization scheme, does not need to be dereferencable
term	required	string	None	The name of the category, in the context of the scheme, or when scheme is missing, it is relevant only as an opaque string to identify the category.

Meta-data

TBD. See ISSUE-18.

`<time>` element

We discussed at F2F2 basing this on other standards' time representations.
This section now represents times as defined in XML Schema Datatypes.
This is ISSUE-26.

Attributes

Name	Required	Type	Default value	Details
scheme	optional	URI	None	URI that identifies the categorization scheme, does not need to be dereferencable
term	required	string	None	The name of the category, in the context of the scheme, or when scheme is missing, it is relevant only as an opaque string to identify the category.

XML Example

This example was just something I generated while thinking through the XML syntax, it hasn't been updated to be in sync with what is in the document, so it may differ.

XML Schema

This is a very rough RELAX NG schema for the XML syntax. It is not guaranteed to work or be in sync with the rest of the document for now.

Introduction

Terminology

POI Data Model

Geo-reference

Center

Contains

Navigation Point

Contains

Address

Contains

Route

Contains

Area

Contains

Object

Contains

Undetermined

Relative

Map

Location

Contains

Relationship primitive

contained-within

contains

adjacent-to

string primitive

Label primitive

ID primitive

Categorization primitive

meta data primitive

Time primitive

XML Syntax

XML Notation

<pois> element

Attributes

<poi> element

Attributes

Representing coordinates

Attributes

<point> element

Attributes

<location> element

Geo-reference elements

<center> element

<address> element

<navigation-point> element

<area> element

<object> element

Attributes

<undetermined> element

<relative> element

Attributes

<map> element

<relationship> element

Attributes

<label> element

id representation

<category> element

Attributes

Meta-data

<time> element

Attributes

XML Example

XML Schema

Use Cases

Acknowledgements

`<pois>` element

`<poi>` element

`<point>` element

`<location>` element

`<center>` element

`<address>` element

`<navigation-point>` element

`<area>` element

`<object>` element

`<undetermined>` element

`<relative>` element

`<map>` element

`<relationship>` element

`<label>` element

`<category>` element

`<time>` element