Review Comment:
I do recommend to accept this new version for publication. The authors greatly improved the article regarding:
- clarity of the contributions wrt previous work of the authors;
- presentation of the results (self containment);
- amount of new contributions.
1. As requested, the authors did clarify what content is genuine in the article, and what is taken from previous work.
2. The article is self contained, Section 5 now contains
3. The authors added new contributions regarding:
- an other LDM ontology better aligned with the SOSA/SSN standard;
- complexity assessment of the query answering;
- discussion and evaluation of optimization strategies: query rewriting and query evaluation optimization with caching and parallelization.
Overall this article represents an important contribution to the field of spatial-stream query answering. It has a good balance between: application-driven, theoretical, and system implementation and evaluation.
I only have minor comments and detected a few typos:
Figure 2: The top concepts in the text are not the ones depicted in the figure. In particular, Event is not in the figure.
The semantics of role ldm:observes (LDM ontology) seems to be different from the one of sosa:observes.
sosa:observes links a sensor to a property
ldm:observes links an actor (system, sensor, ...) to a result
so when mentioning the role *observe* in p.5:1, it should be clarified which ontology is considered
p3:2:46: a separation between of the top concepts -> delete *of*
p5:1:3-5: This sentence is written twice (also p4:1:40-42)
p5:2:39: v happens during s -> should be p happens during s.
p12:1:10 atomic attributes E -> should be Uc
p12:2:51 B_A -> the indice is
p13: The notation D_k[...] should be explained somewhere
p14:1 (around Eq 8) check use of variables z, w, in Eq and text
p14:2: The use of symbol \boxplus is unclear: sometimes with one indice \psi which is meant to be a query atom (explained lower in the text), sometimes with an indice T (not explained) and a suffix L (window size), sometimes alone.
p16:1:6: or be extracted -> deleted *be*
Example 5.3: the line breaks in the query do not correspond to what is explained in the text
p17:2:39 Datalag -> Datalog
p17:2:42 are not connected the rest -> to the rest
p18:1:1 can not directly lifted -> be lifted
p20:2:44 this line should be deleted
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