Thanks for your comments and feedbacks!
Before we decide to develop the open API, we did some research. The result is: a full SSDP protocol implementation is too heavy for a embedded system, e.g. a WiFi bulb. The resource on a SoC is too constraint, the free RAM is normally around 6~8K in some low-end product. If too much SSDP packages are being received, it will impact the normal lighting control logic.
Suppose we follow the standard SSDP in discovery part, then what about next step? How should we expose our control interface? Normally or per some standard method XML/SOAP or Restful API will be needed to control the device, but all of them are too heavy for us. You may wonder why Hue or Lifx or Wemo can handle this, because they use a much stronger processor with much more resources.
Imagine we can implement Restful API or SOAP in our device, what about next step? Developer still need to check our spec and implement the API defined by us, pass each parameter carefully, which is way different than Hue/Lifx.
So current situation is: there is not a single standard in IOT world that everyone follows, that means developer has to build different handlers to handle devices from different vendors. We hope there will be some standard some day finally, but it will be a long way to go.
Hopefully you can understand my point. Currently, the IOT world is fragmented, we don't know which standard to follow, so we invented the standard that is most suitable for us.