Updated README.md file

Author: coot

README.md

@@ -1,5 +1,6 @@
 # io-sim
 
+
 `IOSim` is an simulator monad which supports:
 
 * asynchronous exceptions
@@ -9,69 +10,75 @@
 * concurrency: both low level `forkIO` as well as `async` style
 * strict STM
 * access to lazy ST
-* schedule discovery (see [IOSimPOR](./how-to-use-IOSimPOR.md))
+* schedule discovery (see [IOSimPOR][io-sim-por-how-to])
 * eventlog
 * dynamic tracing
-* tracing committed changes to `TVar`, `TMVar`s, ...
-* labeling of threads, `TVar`'s, ...
+* tracing committed changes to `TVar`, `TMVar`s, etc.
+* labelling of threads, `TVar`'s, etc.
 
-`io-classes` provide a common interface, which allow to write code which can be
-run in both real `IO` and `IOSim`.  It is a drop-in replacement for `IO`.
+`io-classes` provides an interface, which allows to write code which can be run
+in both real `IO` and `IOSim`.  It is a drop-in replacement for `IO`, and
+supports interfaces commonly known from `base`, `exceptions`, `stm`, `async` or
+`time` packages.
 
 One of the principles of `io-classes` was to stay as close to `IO` as possible,
-thus most of the `IO` instances are directly referring to `base`, `async` api.
+thus most of the `IO` instances are directly referring to `base` or `async` api.
 However we made some differences, which are reported below.
 
 `io-classes` supports a novel hierarchy for error handling monads as well more
 familiar `exception` style.  The new hierarchy provides `bracket` and
 `finally` functions in the `MonadThrow` class, while `catch` style operators
 are provided by a super-class `MonadCatch`.  Both `bracket` and `finally` are
-the most common interface used to write code with robust exception handling,
+the most common functions used to write code with robust exception handling,
 exposing them through the more basic `MonadThrow` class informs the reader
 / reviewer that no tricky error handling is done in that section of the code
 base.
 
 `IOSim` exposes a detailed trace, which can be enhanced by labelling threads,
 or mutable variables, tracing `Dynamic` values (which can be recovered from the
-trace) or simple `String` based tracing.  It has been used to develop & test
-a complex concurrent system ([ouroboros-network][ouroboros-network]), in
-particular
+trace) or simple `String` based tracing.  Although its agnostic with respect to
+the logging framework, it worked of us particularly well using
+[contra-tracer][contra-tracer].  It has been used to develop, test and debug
+a complex, highly-concurrent, distributed system
+([ouroboros-network][ouroboros-network]), in particular
 
 * write network simulations, to verify a complex networking stack;
-* write disk IO simulations, to verify database solution.
+* write disk IO simulations, to verify a database implementation.
+
 
 ## Packages
 
-* `io-sim`: provides two simulator monads: `IOSim` and `IOSimPOR` - an enhanced
-  `IOSim` version with schedule discovery capabilities.
-* `io-classes`: class bases interface
+* `io-sim`: provides two simulator interpreters: `IOSim` and `IOSimPOR` - an
+    enhanced `IOSim` version with schedule discovery capabilities.
+* `io-classes`: class bases interface, which allows to to abstract over the
+    monad
 * `strict-stm`: strict STM operations
 
-[ouroboros-network]: https://github.com/input-output-hk/ouroboros-network
-
 
 ## Differences from `base`, `async` or `exceptions` packages
 
+### Major differences
+
 * `threadDelay` is using `DiffTime` (which is measured in _seconds_ rather than _microseconds_).
 * `regiterDelay` is using `DiffTime`
 * `timeout` is using `DiffTime`
 * `getMonotonicTime` returns `Time` (a newtype wrapper around `DiffTime`)
 
+
 ### Minor differences
 
-Some of the types have more general type signatures, e.g.
+Some of the types have more general kind signatures, e.g.
 
 ```
 type Async :: (Type -> Type) -> Type -> Type
 ```
 
-The first type of kind `Type -> Type` describe the monad which could be
+The first type of kind `Type -> Type` describes the monad which could be
 instantiated to `IO`, `IOSim` or some other monad stack build with monad
 transformers.  The same applies to many other types, e.g. `TVar`, `TMVar`.
 
-The types although similar to the original
-are not the same as the ones that come from `base`, `async`, or
-`excpetions` packages:
+The following types although similar to the originals are not the same as the
+ones that come from `base`, `async`, or `excpetions` packages:
 
 * `Handler` (origin: `base`)
 * `MaskingState` (origin: `base`)
@@ -82,12 +89,15 @@ are not the same as the ones that come from `base`, `async`, or
 
 ### Issues
 
-Although new issues should be reported in this repository, we still have a list
+New issues should be reported in this repository, we still have a list
 of issues opened in the `ouroboros-network` repository:
 
 * [io-sim issues][io-sim-issues]
 * [io-classes issues][io-sim-issues]
 
+[io-sim-por-how-to]: ./io-sim/how-to-use-IOSimPOR.md
 [ouroboros-network]: https://github.com/input-output-hk/ouroboros-network
 [io-sim-issues]: https://github.com/input-output-hk/ouroboros-network/issues?q=is%3Aopen+is%3Aissue+label%3Aio-sim
 [io-classes-issues]: https://github.com/input-output-hk/ouroboros-network/issues?q=is%3Aopen+is%3Aissue+label%3Aio-classes
+[contra-tracer]: https://hackage.haskell.org/package/contra-tracer
+[io-sim-por]: https://github.com/input-output-hk/io-sim/blob/main/io-sim/how-to-use-IOSimPOR.md