It is known as Web services map services to deploy vector cartography or Raster served via Internet or intranet using the WMS standard promoted by the TC211 Commission of the OGC, Open Geospatial Consortium. Basically, what this service does is to display as an image one or several layers with a symbology and transparency that is defined in the system that sends the data. This can be dispatched with ArcGIS Server, Geoserver, MapServer, or many others.
There are many reasons to implement it, one of which is to serve data outwards, but it is not the only one.
In the internal case, instead of users calling an orthophoto stored in one place as individual files (from which a copy could be stolen), an image service could be created that would make things easier. They no longer require being called each image of a mosaic, but the system displays what corresponds according to the display.
Let's see how Bentley Microstation does it.
This is done from the Raster Manager, selecting the option to create a new WMS.
We must indicate the address of the WMS service, in this case:
For example, if I request the services of the cadastre of Spain, using this address:
I return all possibilities of data served via wms
The button "Add to map»Serves to choose one or several layers. If several are added, they will all come as a single service, in the order decided here. If added separately, they can be turned off separately.
It is also possible to save the image format, change the coordinate system and display coordinates.
Then there is the button to save and continue editing (Save...) and to save and attach (Save and Attach...) Microstation what it does with this, is to create an xml file where the data call properties are stored, this has extension .xwms.
Then only the xwms files are called when they are required, and it is like having a common raster layer with option to change order, transparency, etc.
It is clear that the WMS service is read only, since it is a representation in the form of an image. To call vector services we should call Web Feature Services (WFS), with which you can not only consult tabular data and thematize but also edit. But that is the subject of another article and another story that in the case of Bentley already has its days.