Improve Step 1 instructions and the description of physical connections.

Author: hokeun

01-actor-model.md

@@ -10,7 +10,7 @@ Operators at either location can issue dispatch commands:
 
 Every dispatch command from either node must be seen by both nodes, so both copies of the grid balance stay in sync.
 
-> **Why two copies?** Redundancy. If one control center loses network connectivity, it can still read the last-known balance and issue local dispatch decisions. This is the fundamental driver of distributed state.
+> **Why two copies?** Redundancy and availability. If one control center loses network connectivity, it can still read the last-known balance and issue local dispatch decisions. This is the fundamental driver of distributed state.
 
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@@ -23,7 +23,7 @@ Here is what our system looks like:
 ![Step 1 actor model diagram](fig/Step1_Actor.svg)
 
 
-The squiggly arrows (`~>`) are **physical connections** in Lingua Franca: they use TCP for reliable in-order delivery on each link, but carry **no timestamp coordination** between links. Messages from California and New York may arrive at either grid manager in any order.
+The squiggly arrows (`~>`) are [**physical connections** in Lingua Franca](https://www.lf-lang.org/docs/writing-reactors/composing-reactors/#physical-connections). They still use TCP for reliable, in-order delivery on each individual link, but the receiver assigns the incoming message a logical timestamp based on its own physical clock (device's clock) rather than preserving the sender's logical timestamp. As a result, LF does not coordinate a single logical ordering across the California and New York links: messages from the two operators may arrive at either grid manager in either order.
 
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README.md

@@ -1,13 +1,14 @@
 # LF Tutorial @ CPS-IoT Week 2026 - Hands-on Session: Logical Time in Distributed Systems: A Power Grid Tutorial
 
 > **Based on:** ["Logical time in actor systems" by Edward A. Lee (2025)](https://ptolemy.berkeley.edu/~eal/publications/LeeTimeAghaFestschriftPreprint2025.pdf)
+> 
 > **Domain:** Distributed power grid control using Lingua Franca
 
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 ## What This Tutorial Is About
 
-Modern power grids are distributed cyber-physical systems. Generation, transmission, and load are spread across vast geographic areas. Multiple control nodes must coordinate in real time, and they must **agree** on the state of the grid even when separated by hundreds of milliseconds of network latency.
+Modern power grids are distributed cyber-physical systems (CPS). Generation, transmission, and load are spread across vast geographic areas. Multiple control nodes must coordinate in real time, and they must **agree** on the state of the grid even when separated by hundreds of milliseconds of network latency.
 
 This tutorial takes you through a series of progressively more sophisticated designs for a distributed grid controller, using the [Lingua Franca (LF)](https://lf-lang.org/) coordination language. Each design exposes a new problem and motivates the next solution, ending with a hybrid design that separates fast, low-risk commands from slower, strongly consistent decisions.