2. Introduction
A vector tile is a vector representation of geographic data covering a spatially contiguous and rectangular extent
They are similar to raster map tiles, namely to provide support to fast map services which can take advantage of pre-rendering and caching
But, they are different because instead of providing a pre-styled fixed image depiction of the geographic data, they are a vector representation which can be manipulated, e.g. styled, at client-side
Figure from:

3. Vector tiles vs image tiles
Client (not the server) decides on styling
Only need to tile the data once to have multiple maps
Drawn vectors can look better on high-resolution displays
Interaction is better (highlighting objects or getting alphanumeric information associated)

4. Introduction
They can be served through any view service interface that supports raster tiles (e.g. OGC WMTS, TMS or WMS-C)
But, they just happen to be in a different format (i.e. instead of PNG, they may be encoded in GeoJSON or Protocol Buffers).

5. Changes
IR 82: The GetTile operation metadata shall be mapped to the <ows:Operation name="GetTile"> element. Either PNG or GIF format (without LZW compression) shall be supported by the View service [INS NS, Annex III, Part B ].
IR 82: The GetTile operation metadata shall be mapped to the <ows:Operation name="GetTile"> element. Either PNG or GIF format (without LZW compression) shall be supported by the View service [INS NS, Annex III, Part B] and, additionally, MVT, PBF, GeoJSON or TopoJSON for vector tiles.

6. Changes
IR 90: Style shall be mapped to the <Style> element. The human-readable name shall be mapped to the <ows:Title> element and the Unique Identifier shall be mapped to the <ows:Identifier> element.
It must have a different interpretation as the styling is a client-side task with vector tiles. One option is to assume that if you request a certain style, in this context it means that the vector tile has all the information necessary to support the rendering with that style in the client. E.g. if the style requires certain styling based on the “road type” attribute, the vector tiles returned when requesting that style will contain that attribute.

7. Changes
IR 91: As the capabilities document is a mono-lingual document, internationalized legend may be placed in different capabilities document for each value of the LANGUAGE parameter. It shall be mapped with the <ows:LegendURL> element.
Server defined legends do not make sense with vector tiles, as they have to be defined in the client applications.

8. Changes
INSPIRE Get Map operation is mapped with the GetTile operation of OGC WMTS. The formats allowed in the GetTile operation would be:
application/vnd.mapbox-vector-tile
application/x-protobuf;type=mapbox-vector
application/json;type=geojson
application/json;type=topojson

9. Tile Map Service
Get View Service Metadata operation
URL}
Get Map operation
URL}/{z}/{x}/{y}.{extension}

10. Prototype
We have developed our WMTS with all our datasets (HY, RT, LU, GN, AU…)
We have add a component to GeoServer to provide vector tiles in different formats (GeoJSON, TopoJSON, MVT)
We have activated the new formats in GeoWebCache

11. Prototype

12. Prototype

13. Prototype