The Data section

This section contains links to the data configuration engine. As you may guess, to publish a map on the internet with GeoServer, you will need to add spatial data to it. Consider the following screenshot:

In this area, you can configure the data access and the way it is exposed to clients:

• Layer Preview opens a form including every layer published on GeoServer. In addition, if you have not yet added any data to your GeoServer installation, you will find several sample layers already listed. Clicking on the OpenLayers link, which is placed on the right side of the layer name, you can open a sample web application to take a look at what your data looks like.

The Keyhole Markup Language (KML) links let you download the data in a format suitable for preview on Google Earth. There are also several other available formats, listed in the drop-down box on the far right of the line. Consider the following screenshot:

• Workspaces are logical entities useful to classify your data into homogenous groups. You may think of a workspace as your own personal namespace. You can associate many layers to one workspace. You are allowed to have several layers with the same name, as long as they are in different workspaces. You may see in the previous screenshot that workspaces and layers referred to each other separated by a colon. For example, when looking at the list of layers in the Layer Preview, you'll see a number of layer names, such as nurc:Img_Sample. The workspace name is nurc and Img_Sample is the layer name. Consider the following screenshot:

• Stores open a list of the configured data connections. Each store connects the GeoServer to repositories where your data is located. It is located inside a workspace, so it is worth setting one up at the beginning instead of sticking stores in one of the defaults. Of course, a set of default stores exist to let GeoServer use the default layers. In the next chapter, you will create stores and use them to add data to GeoServer. Consider the following screenshot:

• Layers show you the data published from GeoServer with some information. You may see the type of layers in the Type column, with a different icon for vector and raster layers, according to the geometry shape. The Workspace and Store values of each layer are shown. Then, there are the layer Name values, which may differ from the file or table name where the data is stored; a tick mark shows if it is enabled, and the last column shows the Native SRS values. From this section, you can view and edit an existing layer, add (register) a new layer, or delete (unregister) a layer. Consider the following screenshot:

• Layer Groups let you logically merge more layers in a single entity. This way, you can publish something more similar to a complex map, where features of different geometry and properties are represented by different symbols. Layer groups allow you to order your layers to best display your data. For example, if you are creating a map of North America, you might want to show a layer of US states on top of North American coastal lines. Then, on top of the US states, you might want to show borders for counties of those states.
• Styles are XML files containing a detailed description of how a feature type has to be drawn on a map. In this section, you can access the styles list, edit them, and remove them from the GeoServer configuration. To edit styles, you can use the integrated editor--a simple, user-friendly interface to edit styles. As you may have guessed, building a pretty map is strictly related to styles; we will cover this in detail in Chapter 6, Styling Your Layers. Consider the following screenshot:

Jump in and look at the layer previews first. We will be visiting the Layer Preview section many times as we brew up our own layers.