OGC is a standards body which defines a standard interface to GIS resources. WMS is a type of OGC compliant map service which supplies GIS maps using an open standard.

Vantage currently supports ESRI ArcGIS 9.3+ Map services. We have looked at including WMS map services  although there hasn't been demand from existing or prospective clients. With that said, the inclusion of WMS services is fairly straight forward and something we would definitely consider in the future if it was required by a client.