Map every valid next action

Problem

What becomes confusing, fragile, or impossible without understanding map every valid next action? This lesson answers that through explanation, a worked example, two runnable exercises, and a reference solution. No teacher-supplied worksheet is required.

HTTP and hypertext scale by exchanging representations through standardized methods, status codes, headers, links, and forms.

Concept explanation

Map every valid next action belongs to “Hypermedia controls state”. map every valid next action is retrieval day: rebuild core behavior without notes, then compare evidence and teach corrections.

For map every valid next action, trace concrete input, state transition, output, and failure through a request/response contract whose method, status, headers, representation, and next actions are observable.

A client sends a request; a server returns a representation plus metadata. Hypermedia controls advertise valid next actions. Apply that model to supplied normal, boundary, and failure cases; each case below names its input and expected evidence.

Example bank

Compare normal, boundary, failure, and cross-layer cases. Predict each observation before revealing the explanation.

Worked example

Start from supplied lab.sh. Focus: Close notes and recreate map every valid next action from blank starting state using: Build three server-rendered states connected only by links and POST forms.

1. Run: chmod +x lab.sh && ./lab.sh
2. Save baseline evidence. Compare curl -v output, request method, status, cache metadata, redirects, and representation bytes.
3. Boundary case: Without rereading, predict and handle: Disable JavaScript and complete full workflow.
4. Failure case: Diagnose from memory, then consult reference only after capturing evidence: Submit invalid transition and return useful 4xx representation with recovery link.

RESULT
Rebuilt version reproduces Every state exposes next valid actions; refresh after POST does not duplicate mutation; failure remains navigable.; correction log names every memory gap. Starter-level baseline: headers.txt begins with an HTTP status line; body.txt contains the representation; byte count is greater than zero.

Starter material

Create lab.sh, paste this exact content, then run the command below.

#!/usr/bin/env sh
set -eu
url="${1:-https://example.com/}"
printf '%s\n' '# map every valid next action'
curl -sS -D headers.txt -o body.txt "$url"
sed -n '1,12p' headers.txt
printf 'body bytes: ' && wc -c < body.txt

STOP / CLEANUPNo background process. Remove headers.txt and body.txt only after saving evidence.

Independent exercise

Teach at three depths: map every valid next action

1. Create second case from blank file: Without rereading, predict and handle: Disable JavaScript and complete full workflow.
2. Then create controlled failure: Diagnose from memory, then consult reference only after capturing evidence: Submit invalid transition and return useful 4xx representation with recovery link.
3. Use curl · Chromium Network · server logs to prove behavior, then repair controlled failure.
4. Compare result against supplied acceptance checks and reference approach before marking complete.

Expected result

• Rebuilt version reproduces Every state exposes next valid actions; refresh after POST does not duplicate mutation; failure remains navigable.; correction log names every memory gap.
• headers.txt begins with an HTTP status line; body.txt contains the representation; byte count is greater than zero.
• Controlled map every valid next action failure produces captured evidence; repair restores stated invariant without hiding error.

Hints

Solution

Attempt both exercises before opening reference approach.