The catalog metadata should also use SensorML where applicable and not contradictory.
e The catalog metadata that can be queried shall be distinguished from the catalog metadata that can only be retrieved. All the catalog metadata that can be queried
should also be able to be retrieved. f The catalog metadata shall be divided into two or more metadata groups suitable for
input at different times. Also, separate metadata groups shall be defined for metadata that is applicable to many images and for metadata that is applicable to single images.
5.5.3 Archive metadata
In addition to the common requirements specified in Subclause 5.2, the image metadata specified for use by OWS 1.2 archive servers shall meet all the following requirements:
a The catalog metadata shall be transferred between clients and servers using XML encoding, with the correct encoding and contents specified using XML Schema.
b The archive metadata should adapt OGC Abstract Specification new Topic 11 which contains ISODIS 19115 to adequately describe all the categories and types of
images handled in OWS 1.2. Such adaptation means selecting a suitable subset of this metadata, and extending that metadata as needed for effective query and retrieval.
NOTE The Future Work clause of OGC document 01-053r1 was accepted as an addition to the
Abstract Specification new Topic 11, but has not yet been physically included in Topic 11. Among other things, that clause states that the “Reference system information” parts of ISO 19115 need to be modified
to be more consistent with the new Abstract Specification Topic 2.
c The catalog metadata should use GML and XML encoding of OGC Abstract Specification Topic 2, wherever applicable, especially for coordinate reference
systems and coordinate operations. d The archive metadata should adapt the FGDC Remote Sensing Extensions as needed
to adequately describe all the categories and types of images handled in OWS 1.2. The catalog metadata should also use SensorML where applicable and not
contradictory.
e The archive metadata shall be divided into two or more metadata groups suitable for input at different times. Also, separate metadata groups shall be defined for metadata
that is applicable to many images and for metadata that is applicable to single images.
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© OGC 2004 – All rights reserved
6 Design principles
6.1.1 Introduction
The following design principles should be considered in specifying the image archive interfaces, image catalog interfaces, and image metadata for the OWS 1.2 testbed.
6.2 General
The general design principles that should be considered include: a Specified services should be as easy-as-practical for a client to use, including by the
programmers of client software, and including clients that use a wide variety of types of geospatial data.
b Specified services should be as easy-as-practical to implement, including by the programmers of the server software.
c Specified services, interfaces, and data structures should be as easy-as-practical to understand, by potential specification users, client users and programmers, data
providers, OGC members, and server programmers. d Specified services should be targeted as a frequently-included part of a set of OGC
web services. e Specifications shall be testable in this testbed. A requirement of the OGC
Interoperability Program is demonstration that all elements in a potential specification can be implemented. Therefore, implementation testing in the form of technology
integration experiments must play a large part in any potential specification’s design.
f When a potential OGC Implementation Specification is developed, that specification shall be accompanied by a comprehensive, completed test suite.
6.3 Compatible, consistent and extensible
The compatibility, consistency, and extensibility design principles that should be considered include:
a Revised and new services should have client interfaces that are similar to the already- approved OGC web services and associated data format specifications, including
WMS, WFS, GML, SLD, and Filter Encoding. b Revisions of already-approved OGC web services and associated data formats
specifications should be maximally compatible with the previous versions. c All aspects of a specification should be maximally compatible with other aspects of
that specification.
© OGC 2004 – All rights reserved
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