A succinct and useful summary of the functionality and technologies behind a range of IoT platforms is presented in a paper by Mineraud et al. (2015). A couple of comments in the paper caught my eye:
As data is the core of the wealth produced by the IoT,
mechanisms must be available to ensure the sharing and fusion
of data streams from local and external data sources. Today’s
IoT solutions do not support, or support in a limited fashion,
the fusion and sharing of data streams. Yet, it remains possible
to combine multiple streams into a single application if one
knows the URI to the desired sources of information, but
this represents a technical challenge for application developers.
…The principle of data fusion has already been applied to RSS
feeds by the web service Yahoo! pipes, which enables the
aggregation, manipulation, mashup and fusion of RSS feeds
into one. Hence, such mechanisms support the creation of
innovative and enriched web content. We suggest that such
mechanisms should be integrated to IoT middleware systems
to perform similar operations on data streams.
This seems like a reasonable suggestion but my experience of Yahoo! pipes from years ago is that it is not the most robust system and did not really catch on with mashup developers in the way expected. Things may have changed since I played around with the service about 5 years ago but I suspect not.
Additionally,efficient search engines for data streams must be developed
to maximize the quality of services of IoT applications.
Perhaps someone will be able to do what Google did for the WWW all those years ago.
Below is their table of the IoT platforms they surveyed. It is not clear how they measured what the user expectations of these platforms were – this would be very difficult as users are likely to have a range of expectations.