Updating the README file (#1502)

Author: PeterF778

consistent-sampling/README.md

@@ -1,8 +1,15 @@
 # Consistent sampling
 
-This component adds various Sampler implementations for consistent sampling as defined by
+There are two major components included here.
+
+## Original proposal implementation
+
+The original specification for consistent probability sampling is defined by
 <https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/tracestate-probability-sampling.md>
 and <https://github.com/open-telemetry/opentelemetry-specification/pull/2047>.
+It supports sampling probabilities that are power of 2 (1, 1/2, 1/4, ...), and uses 8-bit `r-value` and 8-bit `p-value` in tracestate.
+
+The implementation of this proposal is contained by the package `io/opentelemetry/contrib/sampler/consistent` in this repository and provides various Sampler implementations.
 
 * **ConsistentSampler**:
   abstract base class of all consistent sampler implementations below
@@ -23,6 +30,31 @@ and <https://github.com/open-telemetry/opentelemetry-specification/pull/2047>.
   a rate limiting sampler based on exponential smoothing that dynamically adjusts the sampling
   probability based on the estimated rate of spans occurring to satisfy a given rate of sampled spans
 
+## Current proposal implementation
+
+The current version of the specification for consistent probability sampling is described by
+<https://github.com/open-telemetry/oteps/blob/main/text/trace/0235-sampling-threshold-in-trace-state.md>.
+It uses **56** bits for representing _rejection threshold_, which corresponds to a much wider range of sampling probabilities than the original proposal.
+
+The implementation of the current proposal is contained by the package `io/opentelemetry/contrib/sampler/consistent56` in this repository and provides implementation for a number of different Samplers.
+
+* **ConsistentSampler**
+  abstract base class for all consistent sampler implementations
+* **ComposableSampler**:
+  interface used to build hierarchies of Samplers, see [Composite Samplers](https://github.com/open-telemetry/oteps/pull/250)
+* **ConsistentAlwaysOffSampler**:
+* **ConsistentAlwaysOnSampler**:
+* **ConsistentAnyOfSampler**:
+  allows combining several consistent samplers; it samples when at least one of them would sample,
+* **ConsistentParentBasedSampler**:
+* **ConsistentFixedThresholdSampler**:
+  consistent probability sampler that uses a predefined sampling probability
+* **ConsistentRateLimitingSampler**:
+  a rate limiting sampler based on exponential smoothing that dynamically adjusts the sampling
+  probability based on the estimated rate of spans occurring to satisfy a given rate of sampled spans
+* **ConsistentRuleBasedSampler**
+  a sampler that performs stratified sampling by evaluating qualifying conditions and propagating the sampling decision from one of its delegate samplers
+
 ## Component owners
 
 - [Otmar Ertl](https://github.com/oertl), Dynatrace