dawidwys commented on a change in pull request #19107:
URL: https://github.com/apache/flink/pull/19107#discussion_r827932401
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File path: docs/content/docs/concepts/glossary.md
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@@ -25,182 +25,605 @@ under the License.
# Glossary
+#### Aggregation
+
+Aggregation is an operation that takes multiple values and returns a single
value. When working with
+streams, it generally makes more sense to think in terms of aggregations over
finite windows, rather
+than over the entire stream.
+
+#### (Flink) Application
+
+A Flink application is any user program that submits one or multiple [Flink
Jobs](#flink-job) from its
+`main()` method. The execution of these jobs can happen in a local JVM or on a
remote setup of clusters
+with multiple machines.
+
+The jobs of an application can either be submitted to a long-running [Session
Cluster](#session-cluster),
+to a dedicated [Application Cluster](#application-cluster), or to a [Job
Cluster](#job-cluster).
+
+#### Application Cluster
+
+A Flink application cluster is a dedicated [Flink cluster](#(flink)-cluster)
that only executes
+[Flink jobs](#flink-job) from one [Flink application](#(flink)-application).
The lifetime of the Flink
+cluster is bound to the lifetime of the Flink application.
+
+#### Asynchronous Snapshotting
+
+A form of [snapshotting](#snapshot) that doesn't impede the ongoing stream
processing by allowing an
+operator to continue processing while it stores its state snapshot,
effectively letting the state
+snapshots happen asynchronously in the background.
+
+#### At-least-once
+
+A fault-tolerance guarantee and data delivery approach where multiple attempts
are made at delivering
+an event such that at least one succeeds. This guarantees that nothing is
lost, but you may experience
+duplicated results.
+
+#### At-most-once
+
+A data delivery approach where each event is delivered zero or one times.
There is lower latency but
+events may be lost.
+
+#### Backpressure
+
+A situation where a system is receiving data at a higher rate than it can
process during a temporary
+load spike.
+
+#### Barrier Alignment
+
+For providing exactly-once guarantees, Flink aligns the streams at operators
that receive multiple
+input streams, so that the snapshot will reflect the state resulting from
consuming events from both
+input streams up to (but not past) both barriers.
+
+#### Batch Processing
+
+This is the processing and analysis on a set of data that have already been
stored over a period
+of time (i.e. in groups or batches). The results are usually not available in
real-time. Flink
+executes batch programs as a special case of streaming programs.
+
+#### Bounded Streams
+
+Bounded [DataStreams](#datastream) have a defined start and end. They can be
processed by ingesting
+all data before performing any computations. Ordered ingestion is not required
to process bounded streams
+because a bounded data set can always be sorted. Processing of bounded streams
is also known as
+[batch processing](#batch-processing).
+
+#### Checkpoint
+
+A [snapshot](#snapshot) taken automatically by Flink for the purpose of being
able to recover from
+faults. A checkpoint marks a specific point in each of the input streams along
with the corresponding
+state for each of the operators. Checkpoints can be incremental and unaligned,
and are optimized for
+being restored quickly.
+
+#### Checkpoint Barrier
+
+A special marker that flows along the graph and triggers the checkpointing
process on each of the
+parallel instances of the operators. Checkpoint barriers are injected into the
source operators and
+flow together with the data. If an operator has multiple outputs, it gets
"split" into both of them.
Review comment:
For my taste, `Checkpoint Barrier` and `Barrier Alignment` are kind of
same/redundant.
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