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11 th International Symposium for GIS and Computer Cartography for Coastal Zones Managementa server-side database (Vretanos, 2010). Transactional WFS (WFS-T) is part of the standard that allows the client tocreate, modify, and delete features across the internet (Davis, 2007).Using a server package that supports at least the WMS, WMTS, and WFS standards can maximize interoperabilityof spatial data infrastructures. There are many commercial and open-source map servers available. Two strongopen-source options are MapServer and GeoServer. ArcGIS for Server is a popular commercial option which supportsthe WMS and WFS standards.For data distributed to clients in download form, an important OGC service standard is Catalog Service for theWeb (CSW). A catalog service publishes searchable collections of metadata for geospatial data and services. CSWspecifies client request operations, query language grammar, a set of core attributes to be included in metadata, and acommon record format to be returned by the server (Nebert et al., 2007). Coastal atlases that warehouse a collectionof data and services should provide a CSW in compliance with ISO Standard 19115, the international standard formetadata. Coastal atlases within the U.S. should comply with Federal Geographic Data Committee (FGDC) metadatastandards. The CSW can be implemented through a data search function or catalog application such as opensource GeoNetwork or Esri’s Geoportal Server.Client-Side Web Map DevelopmentThere are two basic architectures for interactive web maps: thick client and thin client. In a thick client setup, aprogram is sent as a package from the server to the client and executed through a browser plug-in, applet, or HTMLelement. These technologies provide robust interactivity, a smooth look and feel, and fast reaction time once loaded,and do not require a stable, high-bandwidth internet connection to run (Vatsavai et al., 2012). Their key disadvantageis subjection to the constraints of the client’s system, as individual users must have the right software installedand adequate processing power to use them. Flash, Silverlight, Java, and Processing can be used to build webmaps, but each requires its own unique programming language. Technologies that take advantage of processingdirectly in the client browser, such as SVG and HTML5 Canvas, rely on JavaScript as their programming language.In a thin client, most or all of the program sits on the host machine, with a server handling requests and returningthe results of the requested operation. Map images and data are generated and stored on the server and returned viaURL (Vatsavai et al., 2012). User interactions with the map result in data passed back and forth from the server viaJavaScript. The downside to this approach is the reliance on a high-speed internet connection between client andserver to achieve adequate response times for user satisfaction (Skarlatidou, 2010). This especially poses a problemfor underserved households, particularly in rural areas with less access to high-speed internet, and mobile devicesthat rely on cellular communication networks (Peterson, 2011).JavaScript web maps are usually created using a mapping library or Application Programming Interfaces (API).Because JavaScript is an open-source language, most mapping code libraries can be combined and built on, providinga great deal of creative license to even novice developers. APIs provided by commercial services such as GoogleMaps, Bing Maps, and ArcGIS Online are designed for use with the provider’s service and typically charge fees forhigh-volume use. Open-source libraries are free and modifiable but may not provide all of the functionality neededto work with a commercial service. Many functions of both commercial and open-source libraries are interchangeable,while each library may do some things better than others (Carrillo, 2012).Popular commercial APIs include Google Maps API v3 and ArcGIS Online. Google features strong documentationand momentum as the largest provider of map tiles, but is difficult to use with OGC-compliant services. ArcGISOnline is compatible with ArcGIS web services and WMS. Popular open-source projects include OpenLayers,which supports all OGC services, and Leaflet, a lightweight library that can access multiple commercial and OGCservices. If the project does not require an innovative design, there are several out-of-the-box web mapping frameworksthat may be used to simplify the development process, such as OpenGeo Suite, GeoMoose, Geomajas, and theentirely cloud-based CartoDB service (Carrillo, 2012).Different libraries support different sets of user interactions. Coastal maps include a diverse mix of land and waterfeatures, so supporting user-friendly layer selection is important for exhibition web maps to display coastal datawithout becoming overly cluttered (Figure 1a). Search, filter query, measurement, and data download features areimportant in a coastal web GIS applications, and may require an additional library or plug-in (e.g., GeoExt). Webbasedgeovisualization maps that facilitate data exploration should be highly interactive, allowing users to view thedata in multiple ways and see linked charts or information graphics (Figure 1b) (MacEachren et al., 1999).162