Web GIS About and Need Arup Dasgupta Honorary

Web GIS – About and Need Arup Dasgupta Honorary Advisor GIS Development

GIS is becoming Ubiquitous User Mobile user Mediator GIS Expert Desktop User Mainframe GIS Applications Software Developer Service Provider

GIS Databases are Distributed Clients User Applications Access to Service transformed data Chaining Metadata search and retrieval Geoprocess Middleware ing Services Catalogs. Metadata update Direct data access Servers Content Repositorie s Features Coverages. Other data

OGIS Model OGIS Consensus Process Open Geodata Interoperability Specification • Open Geodata Model • OGIS Service Model • Information Communities Model Vendors Industry Integrators GIS/RS RDBMS Applications Programs Products Client-Server Technology Distributed Computing Platforms CORBA OLE/COM DCE JAVA Telecommunications Technology DSS Interface

Granularity and Coupling Coarse Grained High-Level Interface (HLI) HTTP & XML SQL Tightly Coupled SQL CORBA COM Low-Level Interface (LLI) Fine Grained Loosely Coupled

Loosely Coupled Architecture ¡ ¡ ¡ ¡ Based on asynchronous communications Provides a lightweight and resilient foundation for applications that do not require tight coordination. Uses a well defined cross-component interface The technology at either end of the interface can be modified without changing any of the other components Allows totally independent teams to build compliant code that has zero impact for builds and source sharing across the teams. This allows massive scaling which is something the industry has had a difficult time with. Facilitates the isolation of architectural boundaries. This provides easier debugging abilities

Loosely Coupled Architecture Platform B Platform A Net • “Datagrams” vs. interfaces • Tightly-coupled vs. looselycoupled • Fine-grain vs. coarse-grain • IT spec dependencies Distributed Servers “Service over the wire”

Disadvantages Assumes anonymous participants and generally benign failure modes ¡ Integrity and survivability in hostile environments generally requires different assumptions. ¡ Can require more design time. ¡ There can be performance impacts ¡

Hybrid Approach OGC Interfaces

Summary ¡ ¡ ¡ ¡ Early programming was tightly coupled Web Services programming is loosely coupled Both have advantages and their place Hybrids are possible Different systems exist to ‘model’ these architectures Simple systems can have an ad hoc design Complex systems need a proper architecture

Elements of a Web GIS ¡ Services l l ¡ Catalogue and Registry Service Web Map Services Web Feature Service Web Coverage Service Specifications l l l Geographical Feature Encoding Feature Styling Specification Web Map Context Specification

Spatial data servers with metadata and Open. GIS Catalogue Server interfaces Data Catalogue Registered geodata metadata Metadata Metadata Metadata Metadata …. . a URL for for for for a a a a feature feature feature feature collection, collection, collection, collection, and and and and a a a a URL URL URL URL Where? When? How? What? Who? Why?

Extensions to Catalogue: Service Registries ¡ Registry Services provide a common mechanism to classify, register, describe, search, maintain and access information about Web resources. l ¡ Service Registries contain metadata about the description of services, their location on the Web, and the means of accessing and using these services (i. e. , interfaces and bindings). Service Registry Services provide access to these metadata and the means for clients and services to bind to the published resource. Experiments using UDDI (Universal Description, Discovery and Integration), WSDL (Web Services Description Language), etc

Spatial services servers with metadata and Open. GIS interfaces Service Catalogues Collection of service metadata Metadata for an online service, and a URL Metadata for an onlinefor service, and a URL an online service, Metadata for an online service, and a URL an online Metadata for an onlinefor service, and a service, Collection of service metadata Registry information model Service information model and a URL Collection of service metadata Metadata for an online service, and a URL Metadata for anservice, onlineand service, Metadata for an online a URL and a URL Metadata for an online a URL and a URL Metadata for anservice, onlineand service, Metadata Metadata a URL for for for an an an online online service, service, and and and a a a URL URL URL Need a Processing Function!

Open. GIS® Web Map Service Specification ¡ ¡ Provides a uniform access interface for Web clients to ask for and receive map “pictures” rendered by map servers on the Internet. Easy to implement l http: //clearinghouse 1. fgdc. gov/scripts/ogc/ms. pl? version=1. 1. 1& request=map&srs=EPSG: 4326&b. Box=-180, -90, 180, 90& width=400&height=200&format=JPEG&styles=BLACK& layers=boundary, coastline, elevation, lakes, rivers&

WMS request flow Web Server Request (HTTP CGI form) Response (JPEG file) Web Browser “get. Map” WMS Request WMS services Native services Geo. Media Auto. CAD Map. Extreme Oracle Minnesota mapserver Arc. IMS Arc. View Arc. GIS

Web Map Service (WMS) can get multiple maps Elevation cloud cover Borders Cities Multiple overlaid maps One Get. Map request:

WMS can’t “give data away. ” Roma WMS Get. Map returns a server’s “dumb” JPEG, GIF or PNG representation of the data on the server. It does NOT return the actual data, only a bitmap of the data.

WMS can query by pointing. WMS Get. Feature. Info returns attribute data for a feature or coverage at a specified point. Lat/Long elev. = 237 m.

Open. GIS® Web Feature Service 1. 1 ¡ ¡ ¡ The WFS operations support INSERT, UPDATE, DELETE, QUERY and DISCOVERY operations on vector geographic features using HTTP as the distributed computing platform. QUERY and DISCOVERY are mandatory. The basic interface, like WMS, allows user/client to specify Bounding Box (AOI) and Coordinate Reference System The WFS FILTER specification defines how to use OGC Query Language to perform query operations (same as Catalog) Returns features as GML 3. 0 encoding (default)

Web Feature Service (WFS) returns data. Web Feature Server Get. Feature request: I-8 7 5 I-295 I-9 Feature & attribute data

Web Feature Service (WFS) gets operable feature data from multiple servers Each layer is data, not merely a view: Elevation Cities Country is: _ Name: Italy _ Population: 57, 500, 000 _ Area: 301, 325 sq km. . . Get. Feature request: Borders Multiple thematic data layers

Web Feature Server enables distributed, vendor-neutral data maintenance. X Turn left ahead!

Web Coverage Service (WCS) 1. 0 ¡ Scope: Retrieval of gridded, swath, TIN or other "coverage" data in binary or other formats (HDF, Geo. TIFF, NITF, Net. CDF, etc. ) l ¡ Elevation, Orthoimagery Operations: l l Get. Capabilities Get. Coverage

Web Feature Server Web Map Server Web Coverage Server

OGC Specifications enable information fusion

Open. GIS® Geography Markup Language (GML) ¡ GML supports encoding of digital feature data, for data communication l ¡ Facilitates interoperability of separately developed applications GML is an application of the e. Xtensible Markup Language (XML) l l l XML is a structured text format for encoding data XML specified by World Wide Web Consortium (W 3 C) GML specifies XML Schemas for standardized XML encoding of geographic features, their geometry, and their attributes

Open. GIS® Style Layer Descriptor Version 1. 0 Controls the presentation (style) of a map portrayal ¡ Allows fine grained control for symbolization on a layer by layer basis ¡ Rule-based ¡ Uses XML ¡ Allows rules for portrayal of points, line strings, polygons, text, and other commonly used geometries. ¡

Open. GIS Styled Layer Descriptor One data file… …many different maps! … and non-graphic portrayals!

Open. GIS ® Web Map Context Specification ¡ Describes a standardized approach to enable the capture and maintenance of the context - or state information - of a Web Map Server (WMS) request so that this information can be reused easily in the future user session.

New Additions ¡ Geographic Objects l The Open. GIS(r) Geographic Objects Implementation Specification ¡ ¡ a set of core packages that support a small set of Geometries, a basic set of renderable Graphics that correspond to those Geometries, 2 D device abstractions (displays, mouse, keyboard, etc. ), supporting classes. GML for JPEG 2000 l This specification defines how GML is to be used within JPEG 2000 based geographic imagery. ¡ ¡ specification of the uses of GML within JPEG 2000 data files packaging mechanisms for including GML within JPEG 2000 data files.

OWS-4 Demonstration

My contact details: A. R. Dasgupta Honorary Advisor, GIS Development and Distinguished Professor, Bhaskaracharya Institute for Space Applications and Geoinformatics, Gandhinagar 382007 Email: arup. dasgupta@gisdevelopment. net Fax: +91 -(79)-23213091 Phone: +91 98253 29382