---
title: SEQUAL — Semiotic Quality Framework for Conceptual Models
type: concept
tags: [bpm, modelling, quality, semiotics, conceptual-modelling, theory]
sources:
  - "[[sources/2006-krogstie-sindre-jorgensen-revised-sequal-framework]]"
  - "[[sources/2018-dumas-fundamentals-of-bpm]]"
created: 2026-05-04
updated: 2026-05-04
---

# SEQUAL — Semiotic Quality Framework

A theoretically-grounded framework for evaluating conceptual-model quality based on semiotic correspondences between sets. Originally proposed by **Lindland, Sindre, Sølvberg (1994)** with three quality levels (syntactic, semantic, pragmatic), later extended by **Krogstie et al.** to cover all eight levels of Stamper's semiotic ladder, and revised by **Krogstie, Sindre & Jørgensen (2006)** for active process models.

## The set-correspondence apparatus

Quality is defined as correspondence between sets of statements:

| Set | Meaning |
|---|---|
| **G** | modelling goals — what the model should achieve |
| **L** | language extension — everything expressible in the chosen modelling language |
| **D** | modelling domain — everything that can be said about the situation at hand |
| **M** | externalised model — the actual model artefact |
| **K_s** | social-actor explicit knowledge |
| **K_m** | modeller explicit knowledge |
| **I** | social-actor interpretation of M |
| **T** | technical-actor interpretation of M (e.g., what software does with the model) |

Quality types are correspondences between these sets (mapped to Stamper's semiotic ladder):

| Quality type | Correspondence | Goal |
|---|---|---|
| **Physical** | externalisation + internalisation of M | Model is available, accessible |
| **Empirical** | M readability | Layout, comprehensibility heuristics |
| **Syntactic** | M ⊆ L | Syntactic correctness |
| **Semantic** | M vs D | Validity (M ⊆ D, no false statements) + Completeness (D ⊆ M, no missing) |
| **Perceived semantic** | I vs K_s | Perceived validity + perceived completeness |
| **Pragmatic** | M vs (I, T) | Comprehension by interpreters |
| **Social** | agreement among I's | Feasible agreement |
| **Organisational** | M fulfilling G | Goal fulfilment |

## Feasibility — why absolute quality is unattainable

Validity (M ⊆ D) and completeness (D ⊆ M) are typically infeasible in absolute terms — D is too large to know fully, and modelling has finite cost. SEQUAL introduces **feasibility** so modelling can terminate when further effort yields less benefit than acceptance. Practical quality is therefore *feasible validity* and *feasible completeness*.

## The 2006 revision (Krogstie, Sindre & Jørgensen)

[[sources/2006-krogstie-sindre-jorgensen-revised-sequal-framework]] reframes SEQUAL for **active process models** — models that don't merely describe reality but actively change it through enactment. Three shortcomings motivate the revision:

1. **Static D**: original SEQUAL treats domain as given; active models change D.
2. **Narrow pragmatic quality**: limited to comprehension where modern semiotics emphasises interpreter *impact* (action).
3. **Knowledge-as-object framing**: original treats models as externalised knowledge; revised view (Polanyi-aligned) treats knowledge as in-mind, with models as supports.

### New sets

- **D^O** — optimal domain (the situation the organisation would or should want).
- **K^N** — knowledge need (what knowledge the organisation needs).

### Three semantic-quality flavours in revised SEQUAL

| Type | Correspondence | Used for |
|---|---|---|
| **Descriptive semantic quality** | M vs D | as-is models — does the model match current reality? |
| **Prescriptive semantic quality** | M vs D^O | to-be models — does the model match desired reality? |
| **Semantic quality** *(formerly "perceived semantic")* | K vs M | does the model fit actual stakeholder knowledge? |

### Articulation / activation dynamic

- **Articulation** (D → M): capturing domain in the model. Manual (human modeller) or automatic (sensors, log mining).
- **Activation** (M → D): model-guided action transforming the domain. Manual (human reads model and acts), automatic (workflow engine interprets), interactive (mixed).

The interplay produces co-evolution between model and domain — the dynamic engine of active modelling.

### Pragmatic quality redefined

Comprehension is necessary but not sufficient. The revised pragmatic quality requires:
- **Learning**: ΔK ∩ K^N (model contributes to filling the knowledge gap).
- **Action**: ΔD toward D^O (model-driven changes move the domain toward the optimum).

This is a more demanding criterion suited to active and interactive process models.

## Where SEQUAL appears in BPM literature

- **[[sources/2018-dumas-fundamentals-of-bpm]] §5.4** distils SEQUAL into a three-aspect tripartite (syntactic / semantic / pragmatic) — more actionable for textbook readers but a simplification of the eight-level scheme.
- **[[sources/2010-mendling-reijers-vanderaalst-7pmg]]** explicitly positions itself against SEQUAL: critiques SEQUAL as "too abstract to be applicable for novices and non-experts" and proposes 7PMG as the operational complement targeting (primarily) pragmatic quality.

## Strengths

- **Theoretical scaffolding** for what model quality even *means* — rooted in semiotics rather than ad hoc engineering checklists.
- **Decoupling of dimensions** — physical/empirical/syntactic/semantic/pragmatic/social/organisational are *orthogonal* — a model can be sound but socially unaccepted, or comprehensible but goal-misaligned.
- **As-is vs to-be distinction** in the revised version maps directly to BPM lifecycle phases: discovery (descriptive) → redesign (prescriptive).
- **Anticipates active/agentic systems** — the activation concept prefigures agentic-BPM execution.

## Limitations (acknowledged by authors)

- **Qualitative, not quantitative** — SEQUAL structures evaluation but does not yield a numeric score. Krogstie et al. note this is *the disability the revision does not fix*.
- **Operationalisation gap**: only syntactic quality has hope of objective measurement; semantic and pragmatic quality involve unknowable sets.
- **Practitioner accessibility**: the framework is too abstract for non-experts to apply directly — hence 7PMG and similar operational distillations.

## Relationship to other quality concepts

| Layer | Concept | Role |
|---|---|---|
| Theoretical scaffold | **SEQUAL** | Defines what quality dimensions exist |
| Textbook tripartite | [[concepts/process-model-quality]] | Distillation of SEQUAL into 3 actionable buckets |
| Operational toolkit | [[concepts/7pmg]] | 7 concrete rules targeting (mostly) pragmatic quality |
| Bottom-up metrics | [[concepts/process-model-complexity-metrics]] | Quantitative measures (size, density, CFC) feeding into pragmatic-quality assessment |
| Formal correctness | [[concepts/soundness]] | Behavioural/structural property — sits inside syntactic-quality bucket |
| Runtime conformance | [[concepts/conformance-checking]] | Model-vs-log dimensions (fitness, precision, generalisation, simplicity) — separate axis |

## Related
[[concepts/process-model-quality]] · [[concepts/7pmg]] · [[concepts/soundness]] · [[concepts/process-model-complexity-metrics]] · [[concepts/agentic-bpm]] (active models prefigure agentic execution) · [[concepts/agent-process-observability]] (articulation/activation = read/write loop)

## Sources
[[sources/2006-krogstie-sindre-jorgensen-revised-sequal-framework]] (primary, revised version) · [[sources/2018-dumas-fundamentals-of-bpm]] (textbook citation)