Process models are used by process professionals across organisations of all sizes to document, improve or automate business processes, and to communicate in an easily understandable way with SMEs. Due to their broad appeal, process models come in a variety of shapes, sizes, colours and flow-directions. Unfortunately, this diversity becomes problematic when existing within a single organisation. The value delivered is significantly reduced by these inconsistent models. Invariably, this causes unnecessary disruption and confusion in the business as users have to interpret and discuss the meaning of process models. Modelling conventions aim to reduce the production of inconsistent models and increase speed of understanding. This article provides an introduction to what process modelling conventions are, and how they are used to create standardised process models that can be used by everyone within the organisation.

What are modelling conventions?

Process modelling conventions are a set of agreed rules that govern the look and feel of all process models created within an organisation or beyond. Modelling conventions can be developed at the start of a new process modelling project; however, they are commonly managed within an organisation’s process modelling practice lead (e.g. Office of BPM). Modelling conventions govern all aspects of a process model: from the basic layout (e.g. model from left-to-right, or top-down) to the naming of specific objects (e.g. activities must start with a verb in the present-tense) and everything in between. Modelling conventions are made available as references to anyone interacting, consuming, authoring, or managing process models.

Conventions can be organised in categories to facilitate their understanding and application, for example:

• Architecture/Decomposition – How many levels of process models exist? What modelling notation is used for each level? How are processes uniquely labelled?
• Objects – What objects are used when modelling a process? What shapes represent these objects? What colouring scheme is selected?
• Layout – Is the model’s flow direction from left-to-right or top-down? Are intersecting lines allowed? What restrictions are placed on the layout size?

Understanding and developing modelling conventions is enhanced by determining the purpose of using those standards.

Why use conventions?

Consider having a convention that states: Each activity must start with a verb and should describe only one process step. This convention clearly indicates that an activity should not be used to summarise several steps. Without this convention, models would inevitably contain activities describing several steps –  for example: “Review project timeline, insert comments and send back to Project Manager”. If every activity were to describe multiple steps, then the models would be inconsistent, and each activity would need to be looked at individually and carefully. Users would take more time to understand the model, and analysing the business process becomes complicated due to the merging of several steps into one.

In general, modellers will always have very different levels of process modelling knowledge, experience and training. Conventions provide a common reference point for them, resulting in process models that have the same look and feel, regardless of who created them in the organisation. This offers a major advantage: consistency, which ensures the organisation can understand the process models – and, therefore, the models are more likely to be used widely. Widespread understanding and use of process models is what makes them valuable.

What is a good convention?

Good conventions set the right modelling boundaries by providing standardised building blocks. Conventions enable each modeller to express process models in the same way, through clearly defined shapes with a standardised look and feel. Good conventions:

• are easy to understand and apply;
• are broadly accepted by model authors and consumers;
• can be quickly learned by new modellers or consumers;
• have been created by a collaboration between the modelling team and the customers of process models;
• have been tested and extensively trialled;
• can be implemented in a process modelling tool (or, if one does not exist, easily described in a list of conventions).

After good conventions are designed and developed, the effort of using them effectively commences. 

How to use conventions?

The first step is to train modellers to understand and applying conventions. Once modellers are successfully trained and start the process modelling effort, conventions play a role at each stage in the model lifecycle:

1. Create – During the initial phase, new models are created and existing ones are revised. Modellers apply conventions when creating or modifying models, which results in a consistent look and feel.
2. Review – Modified or newly created models are reviewed for their accuracy against organisational modelling standards. Inevitably, conventions act as guides of model compliance.
3. Publish – In this final phase, models are made available to the business for consumption. Now the customers and users of process models apply those conventions to easily read and understand them.

Organisations that use a sophisticated process modelling tool may be able to implement modelling conventions within this tool. This is a great way to achieve consistent process models, as everyone with access to the tool can review the existing conventions easily, and automatically check process models for their compliance with them. Furthermore, it allows for simplified testing of new or revised conventions, as the impact of a change can be tested on existing models, and the rework effort can be estimated.

Since conventions are best used by all model creators and consumers, it is important to govern them to ensure effectiveness and sustainability.

How to control conventions?

No matter how well developed conventions are, it is likely that modellers will find themselves in situations where it seems necessary to question the existing conventions. A possible scenario is that a new business process has to be modelled with requirements that exceed conventions. Current conventions might be too restrictive, creating the dilemma for the modeller of having to balance accuracy and conformance, and of ensuring that each process model is fit-for-purpose.

There are different ways dealing with these situations. The recommended way is for the modelling team to revisit the existing conventions, take the case at hand, and analyse the gaps. This might result in either a revision of existing conventions, or a solution to the case at hand that is both compliant with the conventions and satisfies the modelling requirements. This simple escalation process ensures that the model’s quality remains high, regardless of any day-to-day issues the modelling team might encounter.

Depending on the scale of the modelling efforts, it is suggested that modelling practice leads regularly meet to work on difficult cases, revisit existing conventions, and discuss suggestions for changes. Modellers should be comfortable and aligned with the idea that modelling conventions are there to improve model quality and consistency.

In conclusion, process modelling conventions are essential to ensure that process models are valuable to the organisation. A broad understanding of the use of process models is only secured if they have a standardised look and feel – which is governed and enforced through conventions. As modelling requirements change, so too must modelling conventions. They are not set in stone, but need to be regularly revisited and adjusted to new or changing needs.