DSMA 2026 EXAM

Multiset of a data stream?

$$A=\left(B,f\right)$$

where B is set of stream elements and f is a function

$$f:B\to\mathbb{N}$$

Support of a multiset A?

Content of the stream S at time j?

where m0, …, mj are the multiplicities of the stream elements

Temporal ordering definition?

Time domain definition?

Operators on a stream?

List the different stream operators

• Create stream

• Stream to relation

• Relation to relation

• Relation to stream

• Stream to stream

Continuous queries definition?

Union of subsets Q(S(ts)) of qualifying tuples produced from a series of Q on successive stream contents.

Monotonic continuous query?

A continuous query is considered monotonic if its result set only grows over time, meaning any output generated at an earlier point remains a valid part of the answer in the future. Because previous data is never retracted, the total result at the current time can be computed simply by taking the initial state and continually adding the new, incremental changes produced at each subsequent time step.

Monotonic continuous query mathematical definition?

• Newer output must contain older output

Blocking vs non-blocking operators?

Non-blocking i fit does not wait until it has seen the entire input, before producing results.

Stateless vs stateful operators?

Stateful operators need to maintain states to produce results (joins, intersection). Stateless process new tuples on the fly without storing temporary results (selection, union).

Definition of a window?

Window definition by words?

A window is a finite subset of a data stream that contains only the items satisfying a condition E at a given time. As the stream changes over time, the window is re-evaluated, but its size always remains finite (bounded by n).

Definition of time-based windows?

Tuple-based window?