MapBase - map service extensions embbed in spatial database [embed read embed]

Traditionally, to provide Web Map Service (WMS), a program named "Map Server" must be run as a standalone process to create map images. Map server receives the requests from the clients, construct SQL statements and send them to spatial database. Spatial database execute the SQL statements and send the results to map server. Map server gets the features, render map images and send them to clients. In this way, map images can't be "select" from spatial database directly. In this work, the authors present extensions embedded in spatial database to enable the database can provide map service without any map servers. First, we implement a "Map Render" which can draw geometry on a canvas. Second, we give "Symbol" data type extension. Different symbols of a geometry may enable the geometry have different map expressions. The spatial database powered by "Map Render" and "Symbol" data type extensions was named "MapBase" by the authors. It is very simple to "select" a map image from "MapBase" directly by SQL statements. Finally, we give an example to explain how to use "MapBase".