7PMG — Seven Process Modeling Guidelines

Seven empirically-grounded, language-agnostic guidelines for producing process models that are easier to understand and less error-prone. Synthesised by Mendling, Reijers and van der Aalst (2010) from prior empirical studies on model size, complexity, structuredness and label ambiguity.

Each guideline is a transformation that preserves behaviour (modulo branching bisimulation): the resulting model expresses the same possible executions, just in a more readable form.

The seven guidelines

#	Guideline	Empirical basis
G1	Use as few elements as possible	Size correlates with both error probability and lower understandability (SAP Reference Model 600 EPCs; 2000 industrial EPCs)
G2	Minimise the routing paths per element	Connector degree (in-arcs + out-arcs) negatively correlates with understanding and positively with errors
G3	Use one start and one end event	Multiple starts/ends correlate with higher error probability; workflow engines often require single start/end; a single start/end is required to apply concepts/soundness checks
G4	Model as structured as possible	Each split connector should be matched by a join of the same type ("balanced brackets"). Unstructured models are both more error-prone and harder to understand
G5	Avoid OR routing elements	OR-join semantics carries known paradoxes and implementation problems; AND/XOR-only models are less error-prone empirically
G6	Use verb-object activity labels (e.g. "Inform complainant")	Significantly less ambiguous and more useful than action-noun ("Complaint analysis") or other styles in controlled n=29 experiment
G7	Decompose model if it has more than 50 elements	Error probability rises above 50% beyond this threshold; split single-entry/single-exit subcomponents into sub-process models

Empirical ground truth

7PMG distinguishes itself from prior frameworks (SEQUAL, GoM) by being operational and empirically grounded. The three measurement axes:

Process model understanding — questionnaire studies (n=73) measuring comprehension against structural metrics.
Error probability — relaxed soundness (600 SAP EPCs) and EPC Soundness (2000 industrial EPCs); structural-metric-based prediction functions for error probability.
Label ambiguity — controlled labelling-style experiments (n=29 postgraduates).

This grounding lets each guideline cite a specific study; cf. sources/2010-mendling-reijers-vanderaalst-7pmg §3.2.

Guideline interactions

The guidelines can conflict: applying G2 (reduce connector degree) typically requires adding connectors, increasing element count and tensing with G1. The 7PMG paper offers a workshop-derived priority ordering from 21 professional modellers (German + Dutch practice) but acknowledges that a theoretically-motivated, empirically-validated prioritisation is out of scope.

A practical heuristic: apply guidelines in the order they reduce model size first (G1, G7), then improve structure (G3, G4), then handle local routing (G2, G5), then labels (G6).

Scope and limitations

Control-flow only. 7PMG does not cover data, organisation, compliance, or non-functional dimensions.
Behaviour-preserving transformations only — 7PMG describes transformations within an equivalence class of models with the same behaviour. Redesign (changing what the process does) is a separate activity (see methods/process-redesign-heuristics, concepts/devils-quadrangle).
Heuristic, not formal. G1, G2, G7 are size/complexity heuristics. They reduce error probability but do not guarantee correctness — for that, pair with concepts/soundness verification.
Empirical foundation is EPC-heavy. Studies were conducted predominantly on EPCs and SAP-style models. Direct re-validation on BPMN corpora has been partial (replication studies exist but are smaller).

Relationship to other quality frameworks

Framework	Layer	Relation to 7PMG
concepts/sequal-framework (Krogstie)	Theoretical (semiotic)	7PMG operationalises SEQUAL's pragmatic + (partially) syntactic quality
concepts/process-model-quality (Dumas)	Textbook tripartite	7PMG is the operational toolkit for pragmatic quality (§5.4.4)
concepts/soundness (van der Aalst)	Formal correctness	Complementary — 7PMG addresses understandability/error-prevention; soundness addresses structural correctness
concepts/process-model-complexity-metrics	Bottom-up metrics	7PMG distils these metrics into actionable rules

Application — worked example

The 7PMG paper transforms a 37-element complaint-handling EPC (multiple starts/ends, OR-join, mixed labels) into a 31-element model with single start/single end, structured nesting, no OR-join, verb-object labels — same behaviour, demonstrably more readable. See sources/2010-mendling-reijers-vanderaalst-7pmg §3.4 for full walk-through.

Practical use as a checklist

For an as-is BPMN model produced from interviews (syntheses/interview-structuring-for-process-models):

Count elements (G1) — flag if growing.
Single start, single end? (G3) — required.
Unbalanced splits/joins? (G4) — restructure where possible.
OR-gateway present? (G5) — replace with XOR + default branch unless inclusive semantics is genuinely needed.
Connector degree ≥ 4? (G2) — split into smaller connectors.
All labels verb-object? (G6) — re-label.
Total elements > 50? (G7) — extract sub-processes.

concepts/process-model-quality · concepts/sequal-framework · concepts/soundness · concepts/process-model-complexity-metrics · frameworks/bpmn · entities/jan-mendling · entities/hajo-reijers · entities/wil-van-der-aalst

Source

sources/2010-mendling-reijers-vanderaalst-7pmg (primary) · sources/2018-dumas-fundamentals-of-bpm (textbook citation in §5.4.4)