SDLC vs PDLC : quelle différence, et pourquoi l'IA change tout
SFEIR analysis (consulting-firm voice, "an engineer's reading") articulating two frameworks too often conflated: the **SDLC** (Software Development Life Cycle — *building the software correctly and reliably*) and the **PDLC** (Product Development Life Cycle — *building the right product and succeeding in the market*). Central thesis: the two cycles are not competitors but **nested** — the SDLC is the subset of the PDLC **housed under its development phase**; when a product team reaches the "build" stage, a full SDLC cycle (design → build → test → review → deployment) runs inside it. The SDLC is standardized (**ISO/IEC/IEEE 12207**, 2017 and 2026 editions), with its lineage of models (Waterfall 1970, V-model, iterative/spiral, **Agile 2001**, **DevOps/DevSecOps 2009+**) and its **DORA** metrics (throughput, stability, MTTR, change failure rate). The PDLC, being the umbrella cycle, runs from **ideation/discovery** to **market withdrawal** (not to be confused with the marketing **PLC** of Theodore Levitt, 1965, which describes a *commercial curve*, not *organized work*: "the PLC observes a curve; the PDLC organizes work"). **Tipping point**: the SDLC natively addresses **only one risk in four** — via **Marty Cagan's "Four Big Risks"** framework (Value → PM, Usability → Designer, Feasibility → Lead Engineer, Business viability → PM) — an organization excellent at SDLC but blind to PDLC produces "software nobody wants" — John Cutler's **"feature factory"** (success measured by output, not outcome). **Why AI changes everything**: generative AI **compresses the SDLC** (Google/JetBrains data, May 2026: **~85% of developers** regularly use coding agents, **~41% of new code** is AI-generated; implementation goes from weeks to hours), so the **bottleneck shifts upstream** — deciding *what* to build (Marty Cagan, April 2026: "when the cost of delivery collapses, the bottleneck shifts to discovery"). Consequences: DORA 2025 (~5,000 professionals, 90% AI adoption) shows a **positive correlation with throughput but a negative one with stability** (more unvalidated features means instability and rework); Andrew Ng (AI Startup School, July 2025) reports teams **reversing the "1 PM for 4 engineers" ratio to "2 PMs for 1 engineer"**; and with **spec-driven development**, the PDLC/SDLC boundary becomes **porous** (the product spec becomes directly executable by agents). **What a CIO should take away**: an augmented SDLC becomes a **market standard, not a differentiator** — the junction with the product must be instrumented, **executable specifications** demanded as input, technical metrics cross-referenced with outcome metrics, and the role of "feature supplier" **refused**. For a CPO: the shift of the bottleneck toward discovery is both a **promotion** (product judgment becomes scarce again) and a **notice to act** (industrialize discovery to reach parity with the SDLC). SFEIR's in-house framework ("Designing and building in the agentic era" — **11-phase cycle** + **Software Factory 10x**) is positioned as the answer on the engineering side, with the **articulation of the two cycles** as the next lever. Conclusion: "as code becomes a commodity, margin shifts toward product judgment and governance."
SFEIR (voix éditoriale du cabinet)