01
Behavior
Screens, transactions, calculations, reports, exports, interfaces and runtime behavior reveal the operational contract.
SOFTWARE ENGINEERING · 02
Legacy Application Replacement
Recover the meaning. Prove the successor. Replace the legacy.
Existing software is more than source code. Years of behavior, exceptions, workflows, data structures, interfaces and operational practice accumulate meaning. Replacement begins by reconstructing that Ground before the successor is allowed to take its place.
01 · EXISTING SYSTEM GROUND
The legacy application is evidence.
The existing estate contains facts that a new specification may no longer describe completely. Replacement starts by observing what the system actually is and what it actually does.
02
Data
Schemas, values, historical records, identifiers and relationships expose structures that may be only partially documented.
03
Practice
Human procedures, exceptions, workarounds and sequencing often carry business meaning that is invisible in architecture diagrams.
02 · RECOVER THE MEANING
Preserve semantics, not obsolete mechanisms.
A successor does not need to reproduce the old architecture merely because the old architecture happened to encode the required behavior.
What may change
Language, framework, runtime, storage, interface design, deployment topology and internal representation can be reconstructed when a better successor architecture is justified.
What must be understood
Business rules, state transitions, required outputs, historical meaning, external contracts and operational invariants must be established well enough to evaluate the successor.
03 · RECONNAISSANCE
Ask the Machine before asking the migration to guess.
Bounded read-only reconnaissance turns existing software and data into explicit Machine Ground. AI reasoning can then work from observed facts instead of reconstructing the legacy estate from incomplete memory.
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01
Inventory the estate
Establish repositories, files, schemas, interfaces, dependencies, reports, processes and relevant runtime surfaces.
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02
Observe actual behavior
Use Machine Evidence to distinguish what exists from what old documentation says should exist.
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03
Reconstruct semantic Ground
Convert discovered rules, structures and relationships into durable Ground for successor design.
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04
Expose uncertainty
Separate demonstrated facts from unresolved interpretation before consequential replacement decisions are authorized.
04 · CONSTRUCT THE SUCCESSOR
Build forward from recovered Ground.
The successor is developed as new software rather than as an uncontrolled translation of the old codebase.
H
Human authority
The Operator decides which recovered semantics matter, what the successor should become and whether demonstrated parity is sufficient.
AI
AI reasoning
AI helps interpret legacy Ground, design the successor, identify uncertainty and translate objectives into bounded Machine work.
M
Machine proof
The Machine constructs, compares, tests and returns Evidence about the actual successor state.
05 · REPLACEMENT PRINCIPLE
Do not preserve the legacy because it is old. Preserve the meaning because it is required.
06 · PROVE THE SUCCESSOR
Replacement requires demonstrated equivalence where equivalence matters.
The successor can be tested against recovered legacy Ground through deterministic comparisons, known cases, state transitions and end-to-end behavior.
01
Traceability
Important successor behavior can be traced to recovered legacy Ground, explicit Objectives and Machine Evidence.
02
Deterministic comparison
Where outputs can be computed, compare them directly rather than asking AI to judge parity from prose.
03
Repair forward
When a parity check fails, preserve demonstrated successor work and repair from the exact observed boundary.
04
CandidateRevision
Freeze the exact complete prospective successor state before consequential replacement.
05
Rehearsal
Exercise the frozen Candidate end to end without granting it Human authority.
06
Human Acceptance
Machine Evidence and Evaluation support the decision. The Human determines whether the successor becomes accepted Source.
07 · PROVENANCE
Know why the successor says what it says.
Replacement becomes safer when reconstructed rules and outcomes retain a path back to the source material, Machine observation or Human decision that established them.
Source-system authority
During reconstruction, the existing system remains authoritative for the facts it actually contains until a successor state is explicitly accepted.
Evidence before interpretation
Machine-observed facts and AI interpretation remain distinguishable so uncertainty is visible instead of silently converted into fact.
Accepted Source
A demonstrated successor becomes accepted Ground only after the required Human Authorization and Human Acceptance boundaries.
08 · PRODUCT BOUNDARY
Replacement without pretending recovery is automatic.
It is
- software-assisted reconstruction of an existing application estate;
- successor construction from demonstrated Ground;
- evidence-based comparison and replacement;
- Human-governed transition to accepted Source.
It does not promise
- automatic recovery of every undocumented business rule;
- instant migration from arbitrary legacy systems;
- autonomous AI authority over replacement decisions;
- a mandatory radius19-hosted SaaS environment.
09 · SOFTWARE LICENSE
Replace the application without surrendering the Ground.
Legacy Application Replacement is offered as software under a direct licensing and delivery relationship. The relevant legacy estate, successor requirements and deployment context determine the bounded product configuration.