Getting in Touch with Volunteered Geographic Information Continued from page 51 interface either in the geodatabase or in ArcMap by changing the attribute table for that feature class. You can hide fields by changing their visibility in ArcMap. Do not hide the Shape field—doing this will prevent the geometry for that layer from displaying in the Web application. Fields can also be made read-only. The order of the fields is defined in the feature class schema—not in ArcMap by changing the layer properties.  When publishing the map document that will be the source for the editing service, include only layers that will be edited in the Web application. Basemap layers and operational layers that will not be edited in the Web editing application should be published to separate services and mashed up with the editing service in the Web application. Creating a Feature Template A feature template packages the settings that have been defined in ArcMap and makes them available to the Web service that will be used for editing. Feature templates define the feature editing experience as well as the information required to create a new feature whether editing in the desktop or the Web. This information includes the layer where the new feature will be stored, the attributes a new feature will be created with, and the default tool used to create that feature. New feature templates are created, and existing ones are edited in ArcMap. Feature templates are saved with the map document used to create them. When creating a feature template, you will notice that ArcMap layers that are symbolized with either unique value or categorical renderers will have each symbol category exposed as a separate layer in the feature template (and subsequently in the Web editing user interface). When the feature class is also subtyped, each category in the feature template will also maintain the default attribute values as defined for that subtype. If you are not using subtypes, set the default field value for each feature template where appropriate. This makes the attribute editing experience intuitive for end users. Publishing the Map and Enabling Feature Access on the Service Finally, the map document is published to ArcGIS Server with both the mapping and feature access capabilities turned on. Both the mapping capability and the Feature Access capability create URLs for the services generated. While a map service serves an image of features, a feature service allows you to serve features over the Internet. Editing on the Web works through a new type of service available with ArcGIS 10: the feature service. In addition to serving features, the feature service also uses the symbology defined in the map document to render the features. Feature service operations include editing and querying. Defining the User Experience The end-user experience is directly affected by the design of the feature class, map document, and feature template. The out-of-thebox Web Mapping API components for editing include the Template Picker, Attribute Inspector, and Attachment Editor.  The Template Picker displays a gallery of templates from one or more feature layers. For each template, the symbol and label defined in the map document is displayed. Note that the application developer can overwrite these symbols in the code.  The Attribute Inspector displays the attributes of selected features from one or more feature layers. If the layer is editable, the feature attributes will be editable. The Attribute Inspector widget honors the domains and subtypes that were defined by the feature service.  The Attachment Editor supports viewing attachments for feature layers that have attachments enabled. If feature layers are from a feature service, the attachment editor will include the ability to create, view, and delete attachments. The application developer/ configurer can also determine which API editing components to include in the Web editing application to tailor the editing experience to the end user and type of content being collected. Administering Ensures the Quality of User-Generated Content A VGI Web site can become unusable if it is not moderated by an administrator. An administrator eliminates offensive language, inaccurate data, content not related to the site’s purpose, and content that could constitute copyright infringement. A best practice for VGI sites is the creation of a simple application that allows non-GIS users to monitor the volunteered content and modify it as needed. Security is another administrative function. Consider implementing ArcGIS Server service security to restrict access to the editable feature service. Remember that the security level is defined at the service level, not feature by feature. Do It Yourself: Use an Existing VGI Sample to Create Your Own VGI Site Follow these steps to use a sample Web application that contains feature editing functionality as a template for creating your own VGI site. This hands-on exercise does not require that you have ArcGIS Server 10 but it does require  A Web browser and access to the Internet  A Web server running on your machine (Microsoft IIS is used in this example.)  A text editor (Microsoft Notepad is used in this example.) View the Live Sample of a Basic VGI App 1. Go to the ArcGIS JavaScript API Resource Center at http://help.arcgis.com/en/webapi/javascript/arcgis/. 2. Click the Samples tab and, under JavaScript API Samples, expand the Editing book. 3. Click the first sample, Default Editor. 4. Click the View live sample link in the Description area and explore This interactive sample is used to demonstrate basic Web editing functionality. Developers can use the sample code to add Web editing to custom Web applications. www.esri.com 52 ArcUser Summer 2010