CEN/TR 15449-3:2012

SLOVENSKI STANDARD
01-januar-2013
1DGRPHãþD
SIST-TP CEN/TR 15449:2011
Geografske informacije - Infrastrukture za prostorske podatke - 3. del: Podatkovno
usmerjen vidik
Geographic information - Spatial data infrastructures - Part 3: Data centric view
Geoinformation - Geodateninfrastrukturen - Teil 3: Datenzentrierte Sicht
Information géographique - Infrastructures de données spatiales - Partie 3: vue centrée
sur les données d'une infrastructure de données spatiales (IDS)
Ta slovenski standard je istoveten z: CEN/TR 15449-3:2012
ICS:
07.040 Astronomija. Geodezija. Astronomy. Geodesy.
Geografija Geography
35.240.70 Uporabniške rešitve IT v IT applications in science
znanosti
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT
CEN/TR 15449-3
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
October 2012
ICS 35.240.70; 07.040 Supersedes CEN/TR 15449:2011
English Version
Geographic information - Spatial data infrastructures - Part 3:
Data centric view
Information géographique - Infrastructures de données Geoinformation - Geodateninfrastrukturen - Teil 3:
spatiales - Partie 3: vue centrée sur les données d'une Datenzentrierte Sicht
infrastructure de données spatiales (IDS)

This Technical Report was approved by CEN on 27 May 2012. It has been drawn up by the Technical Committee CEN/TC 287.

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Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 15449-3:2012: E
worldwide for CEN national Members.

Contents Page
Foreword .4
Introduction .5
1 Scope .7
2 Normative references .7
3 Terms and definitions .7
4 Abbreviated terms .8
5 Data-centric view on SDI . 10
5.1 Introduction . 10
5.2 The model-driven approach . 11
6 Aspects of data specifications . 12
6.1 General . 12
6.2 Semantics and semantic interoperability . 12
6.3 Conceptual schema language . 13
6.3.1 Overview . 13
6.3.2 Relevant standards . 14
6.3.3 Examples and tools . 14
6.4 Application schema . 14
6.4.1 Overview . 14
6.4.2 Relevant standards . 16
6.4.3 Examples and tools . 16
6.5 Features and feature catalogues. 17
6.5.1 Overview . 17
6.5.2 Relevant standards . 18
6.5.3 Examples and tools . 18
6.6 Portrayal . 18
6.6.1 Overview . 18
6.6.2 Relevant standards . 18
6.6.3 Examples and tools . 19
6.7 Encoding . 19
6.7.1 Overview . 19
6.7.2 Relevant standards . 20
7 Data management . 20
7.1 Accessing data . 20
7.2 Quality and conformity of spatial datasets . 20
7.2.1 Overview . 20
7.2.2 Relevant standards . 21
7.3 Spatial referencing. 22
7.3.1 Overview . 22
7.3.2 Relevant standards . 23
7.3.3 Examples and tools . 23
7.4 Identifier management . 23
7.4.1 Overview . 23
7.4.2 Relevant standards . 24
8 Metadata . 24
8.1 Metadata types . 24
8.1.1 Introduction . 24
8.1.2 Discovery metadata . 24
8.1.3 Feature level metadata . 24
8.1.4 Dataset metadata . 24
8.3 Examples and tools . 25
9 Data Product Specification . 25
9.1 Role of a Data Product Specification . 25
9.2 Stepwise approach . 25
9.2.1 General . 25
9.2.2 Step 1 – Use case development . 26
9.2.3 Step 2 – Identification of the user requirements and spatial object types . 27
9.2.4 Step 3 – As-is analysis . 27
9.2.5 Step 4 – Gap analysis . 28
9.2.6 Step 5 – Data Specification Development . 28
9.2.7 Step 6 – Implementation, test and validation . 28
9.2.8 Step 7 – Cost-benefit analysis . 28
9.3 Content of a Data Product Specification . 29
9.4 Relevant standards . 29
9.5 Examples and tools . 29
Bibliography . 30

Foreword
This document (CEN/TR 15449-3:2012) has been prepared by Technical Committee CEN/TC 287
“Geographic information”, the secretariat of which is held by BSI.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes CEN/TR 15449:2011.
The present standard comprises the following parts:
 CEN/TR 15449-1, Geographic information — Spatial data infrastructures — Part 1: Reference model
 CEN/TR 15449-2, Geographic information — Spatial data infrastructures — Part 2: Best practices
 CEN/TR 15449-3, Geographic information — Spatial data infrastructures — Part 3: Data centric view (the
present part);
 CEN/TR 15449-4, Geographic information — Spatial Data Infrastructure — Part 4: Service centric view
Introduction
Spatial data infrastructure (SDI) is a general term for the computerised environment for handling data that
relates to a position on or near the surface of the earth. It may be defined in a range of ways, in different
circumstances, from the local up to the global level.
This Technical Report focuses on the technical aspects of SDIs, thereby limiting the term SDI to mean an
implementation neutral technological infrastructure for geospatial data and services, based upon standards
and specifications. It does not consider an SDI as a carefully designed and dedicated information system;
rather, it is viewed as a collaborative framework of disparate information systems that contain resources that
stakeholders desire to share. The common denominator of SDI resources, which can be data or services, is
their spatial nature. It is understood that the framework is in constant evolution, and that therefore the
requirements for standards and specifications supporting SDI implementations evolve continuously.
SDIs are becoming more and more linked and integrated with systems developed in the context of e-
Government. Important drivers for this evolution are the Digital Agenda for Europe, and related policies (see
Part 1). By sharing emerging requirements at an early stage with the standardization bodies, users of SDIs
can help influence the revision of existing or the conception of new standards.
The users of an SDI are considered to be those individuals or organisations that, in the context of their
business processes, need to share and access geo-resources in a meaningful and sustainable way. Based on
platform- and vendor-neutral standards and specifications, an SDI aims at assisting organisations and
individuals in publishing, finding, delivering, and eventually, using geographic information and services over
the internet across borders of information communities in a more cost-effective manner.
Existing material about SDIs abounds. The criteria used for determining if a given standard or specification is
referred to in this report are that the publication addresses an aspect of SDI, and that it is non-proprietary in
nature.
Based on these considerations, the following reports have been taken into account:
• legal texts and guidelines produced in the context of INSPIRE;
• documents produced by ISO/TC 211 (and co-published by CEN);
• documents produced by the Open Geospatial Consortium (OGC), including the OpenGIS Reference
Model (ORM);
• the European Interoperability Framework and related documents;
• deliverables from the European Union-funded projects (e.g. GIGAS, SANY).
Considering the complexity of the subject and the need to capture and formalise different conceptual and
modelling views, CEN/TR 15449 is comprised of multiple parts:
• Part 1: Reference model: this provides a general context model for the other Parts, applying general IT
architecture standards;
• Part 2: Best Practice: this provides best practices guidance for implementing SDI, through the evaluation
of the projects in the frame of the European Union funding programmes;
• Part 3: Data centric view: this addresses concerns related to the data, which includes application schemas
and metadata;
• Part 4: Service centric view (in preparation): this includes the taxonomy of services, concepts of
interoperability, service architecture, service catalogue, and the underlying IT standards.
Further parts may be added in the future.
1 Scope
Part 3 of the Technical Report describes a data-centric view of a Spatial Data Infrastructure (SDI). The Data
Centric view addresses the concepts of semantic interoperability, the methodology for developing data
specifications through the application of the relevant International Standards, and the content of such
specifications including Application Schemas, Feature Catalogues, General Feature Model, Data Lifecycle
Management and Data Quality, Data Access and Data Transformation.
The intended readership of this Technical Report are those people who are responsible for creating
frameworks for SDI, experts contributing to INSPIRE, experts in information and communication technologies
and e-government that need to familiarise themselves with geographic information and SDI concepts, and
standards developers and writers.
2 Normative references
Not applicable.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
conceptual formalism
set of modelling concepts used to describe a conceptual model
EXAMPLE UML meta model, EXPRESS meta model.
Note 1 to entry: One conceptual formalism can be expressed in several conceptual schema languages.
[SOURCE: EN ISO 19101:2005]
3.2
conceptual model
model that defines concepts of a universe of discourse
[SOURCE: EN ISO 19101:2005]
3.3
conceptual schema
formal description of a conceptual model
[SOURCE: EN ISO 19101:2005]
3.4
conceptual schema language
formal language based on a conceptual formalism for the purpose of representing conceptual schemas
EXAMPLE UML, EXPRESS, IDEF1X.
Note 1 to entry: A conceptual schema language may be lexical or graphical. Several conceptual schema languages
can be based on the same conceptual formalism.
[SOURCE: EN ISO 19101:2005]
3.5
conformance
fulfilment of specified requirements
[SOURCE: EN ISO 19113:2005]
3.6
component
physical, replaceable part of a system that packages implementation and provides the realisation of a set of
interfaces
[SOURCE: ISO/TS 19103:2005]
3.7
identifier
linguistically independent sequence of characters capable of uniquely and permanently identifying that with
which it is associated
[SOURCE: ISO/IEC 11179-3:2003]
3.8
interoperability
capability to communicate, execute programs, or transfer data among various functional units in a manner that
requires the user to have little or no knowledge of the unique characteristics of those units
[SOURCE: ISO/IEC 2382-1:1993]
3.9
reference frame
aggregation of the data needed by different components of an information system
3.10
resource
asset or means that fulfils a requirement
[SOURCE: EN ISO 19115:2005]
3.11
spatial data infrastructure
SDI
policies, standards and procedures under which organisations and technologies interact to foster more
efficient use, management and production of geo-spatial data
[SOURCE: United Nations SDI initiative (UNSDI)]
3.12
Use Case
specification of a sequence of actions, including variants, that a system (or other entity) can perform,
interacting with actors of the system
[SOURCE: OMG UML Specification]
4 Abbreviated terms
API Application Programming Interface
ATS Abstract Test Suite
CEN European Committee for Standardization / Comité Européen de Normalisation
CRS Coordinate Reference System
DCE Distributed Computing Environment
DPS Data Product Specification
ebXML Electronic Business using eXtensible Markup Language
EDR Entity Relationship Diagrams
EN European Standard (CEN deliverable)
EPSG European Petroleum Survey Group
ESDIN European Spatial Data Infrastructure Best Practice Network
INSPIRE Infrastructure for Spatial Information in Europe
IT Information Technology
GEOSS Global Earth Observation System of Systems
GIGAS GEOSS, INSPIRE and GMES an Action in Support
gmd Geographic MetaData
GMES Global Monitoring for Environment and Security
GML Geography Markup Language
GSDI Global Spatial Data Infrastructure Association
IEC International Electrotechnical Commission
ISO International Organisation for Standardization
NMA National Mapping Agency
OCL Object Constraint Language
ODP Open Distributed Processing
OGC Open Geospatial Consortium
OMG Object Management Group
OSI Open System Interconnection
RM-ODP Reference Model of Open Distributed Processing
REST Representational State Transfer
SDI Spatial Data Infrastructure
SOA Service Oriented Architecture
SOAP Simple Object Access Protocol
SQL Standard Query Language
TC Technical Committee
TR Technical Report
TS Technical Specification
UML Unified Modelling Language
UNSDI United Nations SDI
URI Uniform Resource Identifier
UUID Universally Unique Identifier
WSDL Web Service Description Language
XMI eXtensible Markup Interface
XML eXtensible Markup Language
5 Data-centric view on SDI
5.1 Introduction
Exchange of and access to spatial data is the principal objective of an SDI. The data are at the heart of an SDI.
The spatial data in an SDI are a model of the real world. This model is developed according to well defined
methodologies described in different standards. The model is made explicit through a concise description of
data specifications in data specification documents. These specifications can then be used to develop new
datasets or to transform existing datasets to the specifications by mapping the existing model to the model
described in the specifications. In this way, semantic interoperability can be achieved: i.e. different datasets
can be used together and be understood by different users in the same way. Metadata are part of the datasets
and should get proper attention during the data modelling. Metadata will play a crucial role in documenting
and understanding the content of the data model and data product specification, in achieving technical
interoperability.
On top of the data, and by making use of the metadata, services can be built to make the data accessible
through the web and to use them in any information system by viewing, downloading or processing them.
This is often referred to as a Service Oriented Architecture (SOA). A SOA enables new and existing enterprise
systems to share services, information and data across technical platforms, departments and ultimately
across organisational, regional and national boundaries. The benefit is that this leads from a stand-alone
system-centric view to an enterprise data-centric view of IT. The transition to a data-centric SOA allows an
SDI to better leverage new and existing IT investments to support such an infrastructure. The data-centric
transition builds a strategy around the organisations and their geospatial data infrastructure both to preserve
the IT investment and to provide better access to authoritative data sources.
In the next clauses and sub-clauses the data modelling approach, the different aspects and role of data
specifications, as well as the data management aspects are elaborated. The service centric view and SOA will
be further developed in a separate part of this Technical Report. Where appropriate, the relevant international
standards will be summarised and examples of implementations are given, as well as existing tools for
implementation.
5.2 The model-driven approach
The model-driven approach follows the concepts developed in the model-driven architecture defined by
1)
OMG . The lifetime of a technical implementation is shorter than the lifetime of the information it handles.
This makes it necessary to describe the information in a way that allows for new techniques and
implementation environments to be applied.
The starting point of information modelling is the universe of discourse. This is a specific part of the real world
that we want to describe in a model. The universe of discourse may include not only features such as roads,
watercourses, lakes, property boundaries, but also their attributes, their functions and the relationships that
exist among those features. A universe of discourse is described in a conceptual model. This model is
formally represented in one or more conceptual schemas using a conceptual schema language. A conceptual
schema that defines how a universe of discourse is described as data and can be used by one or more
applications, is called an application schema. It provides a description of the semantic structure of the spatial
dataset. The application schema also identifies the spatial object types and reference systems required to
provide a complete description of geographic information in the dataset. Figure 1 describes the relationship
between modelling the real world, the conceptual model and the resulting conceptual schema that represents
it.
Figure 1  The Universe of Discourse as the starting point for conceptual modelling and application
schema (EN ISO 19101)
The EN ISO 19100 series of standards provide the mechanism for such a model-driven approach: the
information is described by a formal, implementation-independent schema. Implementations for various
2)
techniques (e.g. XML file transfer, different types of web services , relational database) and implementation
environments (e.g. J2EE, .Net) can be derived from the schema in a more or less automatic way. Changes in
information requirements are applied to the schema; never directly to the implementation. Figure 2 depicts
these principles.
1) OMG, 2003. Object Management Group, Model Driven Architecture Guide Version 1.0.1. [Online]
http://www.omg.org/mda/ (last visited 2011-11-09).
2) Emphasis has been moving away from SOAP based services towards RESTful services. The latter do not require XML,
SOAP, or WSDL service-API definitions.
Figure 2  The model-driven approach is promoted for SDI development
6 Aspects of data specifications
6.1 General
In this clause several aspects of data specifications are described. First, we explain the basis for data
specifications, the concept of semantics and semantic interoperability. Next, we describe the different aspects
which play an important role in the data specifications development:
 the conceptual schema language used to describe the application schema;
 the application schema itself;
 the features which make up these application schemas and the organisation of features in feature
catalogues;
 portrayal aspects to define the way features are visualised;
 and the implementation through encoding rules.
For each of the aspects we give an overview, the relevant standards and examples and possible tools where
relevant.
6.2 Semantics and semantic interoperability
In general terms, semantics relates to the meaning of words. In the context of spatial data and data
specifications it relates to the meaning of spatial objects and their attributes. While the semantics refer to the
content, the syntax refers to the structuring or ordering of things. In order to reach interoperability, both
elements should be considered.
3)
The information viewpoint from the ISO Reference Model for Open Distributed Processing (RM ODP ) is
focusing on the semantics of information and information processing. A specification developed from this
viewpoint provides a model of the information that could be used in a GIS or similar system. The information
viewpoint is the most important viewpoint for the ISO 19100 series of standards (EN ISO 10101).

3) ISO/IEC – RM ODP: Reference Model for Open Distributed Processing, www.rm-odp.net/ .
Semantic interoperability refers to applications and people interpreting data consistently in the same way in
order to ensure they are understood as it was intended by the creator of the data. Semantic interoperability
may be achieved using translators to convert data from a database to an application. The schemas and
implementations described in the ISO 19100 series of standards support this level of interoperability. To
achieve interoperability between heterogeneous systems two issues need to be addressed. First to define the
semantics of the content and logical structure of geographic data. This should be done in an application
schema. Secondly to define a system and platform independent data structure that can represent data
corresponding to the application schema.
Semantics and syntactic issues become very important when spatial data are interchanged between systems.
This is illustrated in Figure 3. System B has to be able to use data from system A. Data in the data transfer is
structured according to the application schema C and encoded/decoded according to a standard
(EN ISO 19118). M and M are data mappings defining how an existing schema A can be transformed to
AC CB
the application schema C, or vice versa how the data according to the application schema C can be
transformed to an existing schema B. If the data structure of system A or B is different from that of C, such
mappings may be difficult to achieve. However, if the semantics of system A or B are different from that of C,
such mappings may be even impossible to achieve. This makes semantics a very important issue. It is the
application schema C that defines the semantics of the content and the logical structures of the spatial data
and that might make the preservation of the semantics between A and B eventually possible.

Figure 3  Preserving semantics between systems
6.3 Conceptual schema language
6.3.1 Overview
A conceptual schema language is a formal language based on a conceptual formalism (see Figure 1). It
provides the semantic and syntactic elements used to describe the conceptual model rigorously in order to
convey meanings consistently. A conceptual model described using a conceptual schema language is called a
conceptual schema. In order to support the goal of interoperability in the ISO 19100 series of geographic
information standards, conceptual schema language should be used to develop an application schema, data
interchange mechanisms and service implementations (EN ISO 19101). In this case, several platforms can be
supported. Because a conceptual schema language provides a uniform method and format for describing
information, it is possible to read and update the resulting conceptual schema by computer systems as well as
human beings. A conceptual schema language is based upon a conceptual formalism. The conceptual
formalism provides the rules, constraints, inheritance mechanisms, events, functions, processes and other
elements that make up a conceptual schema language. ISO/TS 19103 and ISO 19109 describe how
conceptual schema languages are applied to create application schemas for geographic applications.
A conceptual schema language may have a clearly defined graphical notation (such as UML for class
diagrams) but also a machine-readable format (such as XMI). ISO/TS 19103 specifies the requirements for
conceptual schema languages. ISO/TC 211 has adopted the Unified Modelling Language (UML) as the
conceptual schema language to be used. In order to define requirements and apply constraints to a UML
model, the Object Constraint Language (OCL) has been developed in addition to the UML concepts.
Examples of OCL constraints are:
 the area of a building is at least 25 square metres (context Building; geometry()->area() > 25);
 the startTime of a feature should be before the endTime (context Feature; FeatureStartTime <
FeatureEndTime).
A conceptual modelling language can also be used to model software and hardware, The benefit from this
within the ISO geographic information standards is that the same conceptual schema language (e.g. UML)
can be used for both domain models (information modelling) and for system models (service modelling).
Although the ISO 19000 series has adopted UML as the conceptual schema language to be used, other
languages exist.
6.3.2 Relevant standards
Relevant standards for conceptual schema language are:
 ISO/TS 19103 provides rules and guidelines for the use of a conceptual schema language. It identifies
the combination of the Unified Modelling Language (UML) static structure diagram with its associated
Object Constraint Language (OCL) and a set of basic type definitions as the conceptual schema
language for specification of geographic information.
6.3.3 Examples and tools
Examples of conceptual schema languages are: UML; ArchiMate; Entity Relationship Diagrams (ERD);
EXPRESS; INTERLIS.
6.4 Application schema
6.4.1 Overview
An application schema is a conceptual schema that defines how a universe of discourse is described as data.
Application schemas contain semantics for data interpretation as well as data structures for generation of, for
example, XML-schemas. The application schema provides a description of the semantic structure of the
dataset. The application schema also identifies the spatial feature types, feature attribute types, feature
relationship types and feature operation types. These might originate from a feature catalogue. It also defines
the reference system and quality elements required to provide a complete description of geographic
information in the dataset (see Figure 4). An application schema addresses the logical organisation, rather
than the physical. The purpose of an application schema is:
 to provide a computer-readable data description defining the data structure, which makes it possible to
apply automated mechanisms for data management; and
 to achieve a common and correct understanding of the data, by documenting the data content of the
particular application field, thereby making it possible to unambiguously retrieve information from the data.
In the ISO 19100 series of standards, non-geographic features are also valid. An application schema might be
described explicitly in a conceptual schema language, or might be derived from the internal structure of a
software program.
Figure 4  Application schema and the elements it contains, and the dataset it defines
In order to facilitate automated processing of geographic datasets the elaboration of application schema is
rigorously defined in the ISO 19100 series of standards. According to EN ISO 19109, the development of an
application schema for a specific domain has to follow certain rules. For example, spatial aspects should be
expressed according to EN ISO 19107 while temporal aspects should be expresses according to
EN ISO 19108. On the other hand, there are several manners to ensure flexibility in the application schema:
by using constraints on features and properties (attributes and association roles); by allowing flexible lists of
possible values for an attribute; or by offering options for representing the same real-world phenomena. Figure
5 shows the main steps for implementing a schema derived from a set of specifications.
Figure 5  From specification to application
6.4.2 Relevant standards
Relevant standards for application schema are:
 EN ISO 19107 provides conceptual schemas for describing and manipulating the spatial characteristics of
geographic features. A feature is an abstraction of a real world phenomenon; it is a geographic feature if it
is associated with a location relative to the Earth.
 EN ISO 19108 defines the standard concepts needed to describe the temporal characteristics of
geographic information as they are abstracted from the real world. Temporal characteristics of geographic
information include feature attributes, feature operations, feature associations, and metadata elements
that take a value in the temporal domain.
 EN ISO 19109 defines rules for creating and documenting application schemas, including principles for
the definition of features. An application schema provides the formal description of the data structure and
content required by one or more applications. An application schema contains the descriptions of both
geographic data and related data.
 EN ISO 19137 defines rules for a core profile of the spatial schema specified in ISO 19107 that specifies,
in accordance with ISO 19106, a minimal set of geometric elements necessary for the efficient creation of
application schemata.
6.4.3 Examples and tools
Example of a simple application schema – Energy resources for INSPIRE.
Example of extended application schemas – ESDIN.
6.5 Features and feature catalogues
6.5.1 Overview
A feature is an abstraction of a real world phenomena (EN ISO 19101). A feature concept is a concept that
may be specified as one or more spatial object types or feature types each with a different set of properties
appropriate for a particular application. Examples of feature concepts are ‘road’, ‘river’ or ‘building’.
Registers are used to collect and store all the possible feature concepts, their definitions and all the
information that is necessary to understand the concepts in an unambiguous way. These registers are called
common feature concept dictionaries and are described in EN ISO 19126. They can serve several application
schemas. A common feature concept dictionary is key to reach harmonisation across thematic fields and their
corresponding application schema.
A feature catalogue contains more detailed definitions and descriptions of the spatial object types, their
attributes and associated components occurring in one or more spatial datasets, together with any operations
that may be applied to them. A feature catalogue is linked to an application schema. The way a feature
catalogue is developed is described in EN ISO 19110. A feature catalogue might be automatically derived
from an application schema and might be published via a registry service. Feature catalogues are published
for the purposes of styling into a human readable presentation and access to the individual elements in the
application schema.
Common feature concept dictionaries and feature catalogues are usually multi-lingual. It is believed that
application schemas, feature catalogues and feature concept dictionaries promote the dissemination, sharing,
and use of geographic data through providing a better understanding of the content and meaning of the data
(INSPIRE, 2010). Figure 6 shows the role of the common feature concept dictionary, the feature catalogue
and other data-related components of the SDI.

Figure 6  A common feature concept dictionary provides semantics for application schemas of
different domains
EN ISO 19125 deals with the definition and implementation of simple feature geometries which are supported
by many implementations and used in many operational systems. In practice, many applications go beyond
what Simple Features provides and supports. The standard consists of two parts, a common architecture part
(EN ISO 19125-1), and a part on an SQL option for simple feature access (EN ISO 19125-2) which may be
less relevant for SDI implementation. The GML Simple Features Profile from OGC (OGC, Geography Markup
Language (GML) simple features profile) provides a widely implemented exchange standard for simple
features.
6.5.2 Relevant standards
Relevant standards for features and feature catalogues are:
 EN ISO 19110 defines the methodology for cataloguing feature types. It specifies how a classification of
feature types is organised into a feature catalogue and presented to the users of a set of geographic data.
It applies specifically to the cataloguing of feature types that are represented in digital form but its
principles can be extended to the cataloguing of other forms of geographic data. There exists an
amended version: EN ISO 19110:2005/Amd-1:2011.
 EN ISO 19125-1 defines the simple feature model. It is an abstract model independent from any
computer platform. Simple features are geometries restricted to two dimensions with linear interpolations
between the vertices and containing spatial and non-spatial attributes.
 EN ISO 19125-2 defines a database access of simple features through an SQL interface.
 EN ISO 19126 specifies a schema for feature concept dictionaries to be established and managed as
registers. It does not specify schemas for feature catalogues or for the management of feature catalogues
as registers. However, because feature catalogue are often derived from feature concept dictionaries,
EN ISO 19126 specifies a schema for a hierarchical register of feature concept dictionaries and feature
catalogues. These registers are in accordance with EN ISO 19135.
 OGC Geography Markup Language (GML) simple features profile defines a simplified profile of GML 3.2
that supports GML features and a limited set of geometric types. A set of application schema encoding
rules is defined that allow features to be encoded using GML application schemas.
6.5.3 Examples and tools
Feature catalogue of protected sites.
6.6 Portrayal
6.6.1 Overview
In general terms, portrayal refers to a representation by picture or symbols. Cartographic portrayal relates to
the representation of spatial datasets. It is important as an aid to immediate user understanding. In the context
of SDI, it defines the way graphic output is created for datasets and metadata of the ISO 19100 family of
standards. However, the EN ISO 19117 standard does not include standardisation of cartographic symbols.
The cartographic symbolisation itself is kept separate from the feature types of the dataset. The definition of
4)
the cartographic representation of a feature is stored in a portrayal catalogue .
The portrayal within the context of data specifications will define all the portrayal rules for data. These rules
might be defined by the thematic communities. They will clarify how standardised portrayal catalogues can be
used to harmonise the portrayal of data across the different view services that will be developed on top of the
datasets. In practice, the portrayal rules define how each spatial feature of a dataset will be depicted. Rules
can vary from simple to more complex. For example a black solid line, 1 pixel, for a simple road; or a double
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