The Next Wave of Interoperability Via Web Services

Rarely has a better match been made than be- This is where Web services and standards is a productization of a suite of OGC-compliant tween the collective capabilities of GIS and the organizations such as OGC and International server connectors for ArcIMS, client plug-ins distributive capabilities of the Web. The power Organization for Standardization (ISO) enter for desktop products in ArcGIS, and toolkit of the Web to reach anywhere in the world for the equation. Web services utilize an evolving additions for custom thin client development content rests on standard protocols such as set of XML message standards to make spe- using JavaServer Pages (JSP). TCP/IP and HTTP, which enable diverse com- cific geospatial software functionality, such as puter technologies to form a single community. finding the location of an address, able to be WMS and WFS Connectors for ArcIMS A worldwide geographic community is also be- discovered and requested meaningfully over The ArcGIS Interoperability Toolkit contains ing built on evolving standards for the specific the Web without regard to the specific under- two newly updated connectors for ArcIMS. exchange of GIS content and services. lying technology supplying that functionality. The OGC WMS connector enables ArcIMS ESRIʼs long-standing commitment to stan- The consumer of such a Web service may only to provide Web map services that fully imple- dards and interoperability in the geospatial be able to guess from the speed of response ment the current OpenGIS realm has taken a significant step forward whether the result was supplied by an ArcGIS Specification. In particular, this component with the introduction of the ArcGIS Interoper- geocoder or by a roomful of computer opera- responds to OGC WMS requests and supports ability Toolkit. The toolkit represents the pro- tors with phonebooks. Its functionality and use dynamic styling of maps through the OGC ductization of a set of Open GIS Consortium are the same. SLD encoding as part of a GetMap request. (OGC) compatible interface connectors for The OGC and ISO have pursued a series This component also supports dynamic speci- use with ESRI Web-enabled software. It will of geospatial content encoding standards and fication of features (UserLayer), either in-line empower ArcGIS users to exchange geospa- service interface specifications in the Web or through a WFS GetFeature request to a re- tial information not only with every other con- services paradigm, utilizing XML for the col- mote service, which is then rendered on top of nected ArcGIS user but also with users of any laborative discovery, exchange, display, and the other requested map layers. It supports the other software compatible with those same analysis of spatial content. Chief among these GetFeatureInfo request to provide information interfaces. are the Web Map Service (WMS) and Web (e.g., GML-encoded features) about a location Feature Service (WFS) interface specifications within a requested map. In addition, it responds Why Standards and Interoperability? as well as the Geography Markup Language to GetCapabilities requests with appropriate The toolkit is an embodiment of the philosophy (GML) and (SLD) service and content information about itself to that, in order to fully realize the global capabil- encoding standards. facilitate discovery of its offerings from across ity and benefits of geographic information and From the initial efforts of OGC to establish the Web. GIS technology, spatial data must be able to be the OpenGIS Specification A single connector installation will sup- shared with ease and dynamically integrated to the most recent Open Web Services work, port multiple dynamic service endpoints cor- into highly distributed, enterprise-scale ap- ESRI has maintained a leadership role as a responding to multiple map services within plications. Such ad hoc systems can only be member of the OGC Board of Directors and the ArcIMS instance to which it is installed. built from loosely coupled and freely interoper- the Planning and Technical Committees and In other words, the default behavior will be able components that can be utilized as needed as a participant in numerous test beds, pilot for the connector to expose automatically, for without changing the essential functioning of projects, and specification products published each ArcIMS map service published, a separate the system itself. by OGC. The ArcGIS Interoperability Toolkit WMS endpoint for that map service.

What Is Interoperability? One view of interoperability describes layers of ArcGIS Interoperability Toolkit shared understanding, each layer building more ADAPTED SERVICES SERVICE INTEROPERABILITY TOOLKIT CLIENT TOOLKITS specific meaning on top of the previous layer. (EXAMPLES) The Internet and the Web are themselves built ArcIMS Map Service JSP WMS/WFS/WRS Toolkit on a foundation of layers such as the transport protocol TCP/IP, the conversational protocol HTTP, and the content-encoding standard XML (which can be thought of as a generalization of Web Map Server SLD the HTML found in every Web page). These (WMS–SLD) standard interoperability layers level the Inter- ArcIMS Feature Service ArcGIS WMS/WFS/WRS Plug-Ins net playing field across different computational platforms and technologies. Virtually any Web-enabled device (e.g., Web Feature Server server, desktop computer, mobile phone) can ArcIMS Metadata Service (WFS) exchange XML messages with another such device. But how does a client know it is making the right request and how does the server know it is providing the right information? The solution is straightforward when both Provides Standards-Based Serves Diverse Thick/Thin Client client and server share technology, design, and Front Ends to ESRI Services Applications on Diverse Platforms address books but more difficult for arbitrary components trying to work together in the ad The ArcGIS Interoperability Toolkit represents the productization of a set of Open GIS Consor- hoc spirit of the Web. tium (OGC)-compatible interface connectors for use with ESRI Web-enabled software.

42 ArcUser April–June 2003 www.esri.com Special Section

Three modes of SLD layer/style definition ArcGIS Plug-Ins for WMS, WFS, WRS to high-powered ArcGIS-specific functionality, are supported by the connector. This client toolkit consists of a set of custom enabling each ArcGIS user to choose a balance n NamedLayer/NamedStyle—Preconfigured ArcObjects that enables users of the ArcObjects or mix appropriate for a specific application, map layer, predefined style applications, ArcMap and ArcCatalog, to form rather than have to choose sides. n NamedLayer/UserStyle—Preconfigured map layers from Internet data sources with map layer but with a dynamic feature rendering WMS or WFS interfaces in addition to the ex- Conclusion specified by SLD style elements. isting support for native ArcIMS map services. The ArcGIS Interoperability Toolkit has been n UserLayer/UserStyle—Map features also An additional ArcCatalog plug-in allows users designed to let ArcGIS users have their cake specified dynamically, either via a GetFeature to query service or content metadata from OGC and gobble up the benefits of interoperability call to a remote WFS or through in-line GML, catalogs through the Web Registry Service as well, wherever those benefits have been tar- with dynamic feature rendering specified by (WRS) interface. geted by organizations charged with promoting SLD style elements. The functionality of the plug-ins will follow a level of cross-platform, cross-technology In all cases, the actual SLD map composi- closely the built-in capability of ArcCatalog geospatial integration. The full benefits of in- tion document may either be specified in-line and ArcMap to make use of ArcIMS map ser- teroperability are available to any ArcGIS user. with the map request or referenced by way of vices. Users will be able to connect to a Web Critical layers of geographic information can be a URL. Since the WMS connector will style ei- map or , browse its con- discovered, integrated, queried, and displayed ther preconfigured map layers (NamedLayers) tents, and, in the case of ArcMap, add one or by almost anyone, anywhere, while at the same or external feature collections (UserLayers), it more map layers or feature collections to a map time the custodians of the data can maintain this can be said to function as both an integrated as RasterLayers or FeatureLayers respectively. information as they see fit—maintained locally SLD WMS in the former case and a component Information is returned for any subset of WFS and accessed globally. At the same time, all the SLD WMS in the latter case. feature collections, but only information about advanced functionality of pure ArcGIS solu- The OGC WFS connector enables ArcIMS features at a single point on the image is returned tions is built in and ready for use. to provide Web feature services that implement for WMS layers, consistent with the WMS ESRI has made major investments in the the OpenGIS Web Features Service Specifica- GetFeatureInfo operation. development and implementation of open GIS tion. The connector provides client access to The WRS plug-in will augment the built-in standards not only to serve its customers but geographic (vector) data, supports complex ArcCatalog search functionality by adding an also to promote the sharing of geographic data OGC filter queries, and returns collections of OGC Catalog option to the search dialog sup- across all GIS platforms in the belief this policy features encoded in GML. A particular “shape- porting a small core set of search parameters. will result in the most open and interoperable like” profile of GML has been defined for the GIS technology ever deployed. feature types that may be accessed through the JSP Client Add-In for WMS, WFS, WRS The ArcGIS Interoperability Toolkit will be connector. This component is a toolkit add-in that extends available in the third quarter of 2003. For more An essential characteristic of OGC-style the Java Connector and JSP Toolkit included information, visit www.esri.com/standards. services, such as WMS or WFS, is that they with ArcIMS and enables the Toolkit applica- are self-describing through support for a Get- tions to access WMS, WFS, and WRS services. Global Map/GSDI Capabilities operation. The end user, through The JSP add-in comprises a package of proxy/ any WMS/WFS client, such as a JSP browser helper classes along with a custom tag library Grant Program application or a plug-in equipped ArcCatalog, and sample JSP pages for implementing HTML will be able to invoke the GetCapabilities op- Viewers with or without JavaScript augmenta- In 2002, ESRI made more than eration on a specific service as described above tion. This provides several paths that require 100 Global Map/Global Spatial Data to receive an XML encoding of metadata about minimal XML processing to develop thin cli- Infrastructure (GSDI) grants valued at the service and its content. The service admin- ents that make use of data and services through $50,000 (U.S.) to national agencies. istrator will have two functional options. any combination of ESRI and OGC interfaces. The program, established in memory of n Trigger a refresh of the WMS or WFS ser- The ArcGIS Interoperability Toolkit in- GIS pioneer John E. Estes, has attracted vice metadata from ArcIMS for a given map cludes documentation and installation notes interest from national mapping agencies service. including three installers—the Windows throughout the world. n Update additional metadata that is stored as ArcIMS Installer, the Windows ArcObjects ESRI is underwriting the program one XML document for each service, either as a Installer, and the UNIX ArcIMS Installer. with a comprehensive package of document on disk or as a document maintained software, training, and support to on an ArcIMS Metadata Service. How Much Interoperability encourage the building of national The latter functionality is required for pro- Is Good for You? spatial data infrastructures in countries viding metadata (especially content metadata) This may sound paradoxical, but the real goal around the world. The program will also to be accessed through the WMS or WFS in- of the ArcGIS Interoperability Toolkit is oper- promote the sharing of geospatial data terface that is not provided by ArcIMS directly. ability. While interoperability is essential for to expand the GSDI movement. GSDI Initial registration of a map service through the taking advantage of Web-like universal access, provides an important framework of WMS or WFS connector will cause an outline it always comes at the cost of a lowest common standards, policies, data, procedures, XML document to be generated. Subsequent denominator in specific functionality. and technology to support the effective refresh of that metadata will preserve, as much The toolkit allows the fortunate ArcGIS coordination and dissemination of as possible, the additions and modifications user to avoid the horns of this troublesome geographic information. made by the operator. dilemma. It provides a seamless transition from For more information on this high-quality OGC Web Service interoperability program, visit www.esri.com/industries/ internationaldev/grants/index.html. www.esri.com ArcUser April–June 2003 43