RisingWave Community - What are the differences between time-series databases and streaming databases? Are there clear boundaries between them?

Time-series databases are a specialization of OLAP databases, designed to process large amounts of data given user queries.
Streaming databases continuously process queries in an event-driven mode, with predefined queries triggering computations.
Both databases can handle time-series data with timestamps attached to each event.
While there may be some overlap in use cases, time-series databases and streaming databases are distinct and are likely to co-exist for a long time.
RisingWave, a streaming system, does not currently support fully-fledged OLAP queries or columnar stores, as it aims to focus on stream processing before expanding into other domains.