ISO/IEC 15909-3:2021

INTERNATIONAL ISO/IEC
STANDARD 15909-3
First edition
2021-11
Systems and software engineering —
High-level Petri nets —
Part 3:
Extensions and structuring
mechanisms
Ingénierie du logiciel et des systèmes — Réseaux de Petri de haut
niveau —
Partie 3: Extensions et mécanismes de structuration
Reference number
© ISO/IEC 2021
© ISO/IEC 2021
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Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Conformance . 2
4.1 General . 2
4.2 Enrichment process . 2
4.3 Extension process . 2
4.4 Structuring mechanism . 3
5 Enrichment process .3
5.1 General . 3
5.2 Instances of enrichment . 3
5.2.1 General . 3
5.2.2 Inhibitor arcs . 3
5.2.3 Reset arcs . 4
5.2.4 Read arcs . 4
5.2.5 Capacity places . 5
5.3 Generalized enrichment process . 5
5.3.1 General . 5
5.3.2 Definition of Petri nets with enrichment . 5
5.3.3 Definition of enabling rule for Petri nets with enrichment . 6
5.3.4 Filtering function for enrichment . 6
5.3.5 Firing rule for Petri nets with enrichment . 6
5.3.6 Compatibility with extensions . 6
6 Extension process . 6
6.1 General . 6
6.2 An instance of extension: FIFO nets . 6
6.2.1 General . 6
6.2.2 Definition of FIFO nets . 7
6.2.3 Behavioural semantics . 7
6.2.4 Definition of equivalent high-level Petri net . 7
6.2.5 Compatibility with enrichments . 7
6.3 The generalized extension process . 7
6.3.1 General . 7
6.3.2 Definition of the net type . 8
6.3.3 Definition of the behavioural semantics . 8
7 Structuring mechanism.8
7.1 General . 8
7.2 Module definition . 8
7.2.1 Definition of sort generator . 8
7.2.2 Definition of module interface . 9
7.2.3 Definition of module implementation . 9
7.3 Module instantiation . 9
7.3.1 General . 9
7.3.2 Definition of module instances and uses . 9
7.3.3 Definition of module definition . 10
7.3.4 Definition of signature and homomorphisms σ . 11
k
7.3.5 Definition of variables . 11
7.3.6 Definition of algebra .12
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ˆ
7.3.7 Definition of places and transitions T .12
Annex A (informative) Guidelines for graphical notations .13
Bibliography .15
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Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work.
The procedures used to develop this document and those intended for its further maintenance
are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria
needed for the different types of document should be noted. This document was drafted in
accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC
list of patent declarations received (see patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see
www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 7, Software and systems engineering.
A list of all parts in the ISO/IEC 15909 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.
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Introduction
Petri nets have been used to describe a wide range of systems since their invention in 1962. The
technique is mathematically defined and can thus be used to provide unambiguous specifications
and descriptions of applications. It is also an executable technique, allowing specification prototypes
to be developed to test ideas at the earliest and cheapest opportunity. Specifications written in the
technique can be subjected to analysis methods to prove properties about the specifications, before
implementation commences, thus saving on testing and maintenance time and providing a high level of
quality assurance.
A problem with Petri nets is the explosion of the number of elements in their graphical form when they
are used to describe complex systems. High-level Petri nets were developed to overcome this problem
by introducing higher level concepts, such as the use of complex structured data as tokens, and using
algebraic expressions to annotate net elements. The use of “high-level” to describe these Petri nets
is analogous to the use of “high-level” in high-level programming languages (as opposed to assembly
languages), and is the usual term used in the Petri net community. Two of the early forms of high-level
nets that this document builds on are predicate-transition nets and coloured Petri nets, first introduced
in 1979 and developed during the 1980s. It also uses some of the notions developed for algebraic Petri
nets, first introduced in the mid-1980s. It is believed that this document captures the spirit of these
earlier developments (see Bibliography).
The technique has multiple uses. For example, it can be used directly to specify systems or to define
the semantics of other less formal languages. It can also serve to integrate techniques currently used
independently such as state-transition diagrams and data flow diagrams. The technique is particularly
suited to parallel and distributed systems development as it supports concurrency. The technique is
able to specify systems at a level that is independent of the choice of implementation (i.e. by software,
hardware (electronic and/or mechanical) or humans or a combination). This document may be cited
in contracts for the development of systems (particularly distributed systems) or used by application
developers or Petri net tool vendors or users.
The ISO/IEC 15909 series is concerned with defining a modelling language and its transfer format,
known as high-level Petri nets. ISO/IEC 15909-1 provides the mathematical definition of high-level
Petri nets, called the semantic model, the graphical form of the technique, known as high-level Petri net
graphs (HLPNGs), and its mapping to the semantic model. It also introduces some common notational
conventions for HLPNGs.
ISO/IEC 15909-2 defines a transfer format for high-level Petri nets in order to support the exchange of
high-level Petri nets among different tools. This format is called the Petri net markup language (PNML).
Since there are many different types of Petri nets in addition to high-level Petri nets, ISO/IEC 15909-2
defines the core concepts of Petri nets along with an XML syntax, which can be used for exchanging
any kind of Petri nets. Based on this PNML core model, ISO/IEC 15909-2 also defines the transfer
syntax for the types of Petri nets that are defined in ISO/IEC 15909-1: place/transition nets, symmetric
1)
nets , high-level Petri nets, Petri nets with priorities, and Petri nets with time. Place/transition nets
and symmetric nets can be considered to be restricted versions of high-level Petri nets. Petri nets with
priorities and Petri nets with time are considered as extensions of the other types.
This document defines extensions to the types of Petri nets that are defined in ISO/IEC 15909-1.
These extensions comprise enrichments of Petri net types and definitions of new Petri net types. This
document also defines structuring mechanisms for these Petri net types.
In this document, the semantics which is considered is always the interleaving semantics.
This document provides an abstract mathematical syntax and a formal semantics for the technique.
Conformance to the document is possible at several levels. The level of conformance depends on the
class of high-level net chosen. The usual graphical notations are depicted in Annex A.
1) Symmetric nets have been first introduced as well-formed nets and are currently standardized as ISO/IEC
15909-1.
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INTERNATIONAL STANDARD ISO/IEC 15909-3:2021(E)
Systems and software engineering — High-level Petri
nets —
Part 3:
Extensions and structuring mechanisms
1 Scope
This document defines enrichments, extensions and structuring mechanisms of Petri nets, applied on
the definitions proposed in ISO/IEC 15909-1. This document facilitates the definitions of new kinds of
Petri nets and their interoperability, while remaining compatible with those defined in ISO/IEC 15909-
1.
This document is written as a reference for designers of new Petri net variants, by defining common
enrichments, extensions and structuring mechanisms, as well as a generalized process for defining
new ones.
This document is applicable to a wide variety of concurrent discrete event systems and in particular
distributed systems. Generic fields of application include:
— requirements analysis;
— development of specifications, designs and test suites;
— descriptions of existing systems prior to re-engineering;
— modelling business and software processes;
— providing the semantics for concurrent languages;
— simulation of systems to increase confidence;
— formal analysis of the behaviour of systems;
— and development of Petri net support tools.
This document can be applied to the design of a broad range of systems and processes, including
aerospace, air traffic control, avionics, banking, biological and chemical processes, business processes,
communication protocols, computer hardware architectures, control systems, databases, defence
command and control systems, distributed computing, electronic commerce, fault-tolerant systems,
games, hospital procedures, information systems, Internet protocols and applications, legal processes,
logistics, manufacturing systems, metabolic processes, music, nuclear power systems, operating
systems, transport systems (including railway control), security systems, telecommunications and
workflow.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 15909-1, Systems and software engineering — High-level Petri nets — Part 1: Concepts, definitions
and graphical notation
© ISO/IEC 2021 – All rights reserved

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 15909-1 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
capacity
maximum multiset of tokens a capacity place (3.2) can hold
3.2
capacity place
special kind of place that can hold no more than a specified capacity (3.1)
3.3
FIFO
special kind of queue that is operated first in first out
3.4
inhibitor arc
special kind of arc that reverses the logic of an input place
Note 1 to entry: Instead of testing the presence of some tokens in the related place, it tests the lack of these.
3.5
read arc
special kind of arc that tests the presence of some tokens in the related place, without consumption
3.6
reset arc
special kind of arc that empties an input place
3.7
sort generator
generator of new sorts and operators built from a given signature (passed as a parameter)
4 Conformance
4.1 General
There are different levels of conformance to this document.
4.2 Enrichment process
A Petri net model is conformant to the enrichment process level when it contains a subset of the features
defined as enrichments by Clause 5.
4.3 Extension process
A Petri net model is conformant to the extension process level when it contains a single feature defined
as extension by Clause 6.
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