Imixs-Workflow 5.2 Supports Asynchronous Events

With the new release v5.2.0, the open source workflow engine Imixs-Workflow now supports the asynchronous execution of BPMN events.

This feature is a big step forward especially in a microservice architecture. The new so called AsyncEvents make it much more easier to decouple a Rest API call from the processing life cycle of the workflow engine. In this way the request-response pattern shows better performance and allows a very clear design of complex business processes.

The AsyncEvents were already part of the Imixs-Microservice project in a pre-release and become now a core feature of the Imixs-Workflow engine. Especially in more complex architectures, the use of the so-called SAGA Pattern is an important building block. With asynchronous events Imixs-Workflow is now supporting this design pattern as a core feature. Read also our blog about building powerful microservice solutions with the SAGA Pattern.

Microservice Saga Pattern with Imixs-Workflow

In my last blog I explained the core concepts behind the Microservice Saga Pattern. In this blog I will address the problem from a more practical perspective by demonstrating how Imixs-Workflow can be used as a Saga Orchestrator within a Microservice architecture. First, I would like to give a brief review of the main concepts of the saga pattern. Later I show some implementation examples.

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Cloud Native and Business Transactions

Everyone is talking about cloud technologies and of course every modern project relies on a microservice architecture. A variety of technologies and methods contribute to the success of this architecture pattern. But what does cloud native actually mean for the business world? How do companies and organizations implement business processes successfully beyond the big technology promises?

The basic idea of a microservice architecture is to break down the technical requirements of a software system into the smallest possible and therefore manageable services. The advantage: services created in this way can be developed independently of each other with different technologies by different teams. At the same time, we see new methods and technologies to connect, monitor and scale these services.

But just looking at the technology does’t mean that software can be developed faster and better. I would therefore like to compare some of these methods and technologies from the microservice architecture with the requirements for the development of business applications.

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BPMN 2.0 – The Extension Mechansim

The ‘Business Process Model And Notation’ standard is a well designed notation for describing business workflows. BPMN 2.0 becomes the standard for modeling business logic and fits very well the model driven software design in agile software projects.

The BPMN language, which is based on XML, was intended for users at all levels, from the business analysts who create the initial design, to the developers who implement the technical details, and finally, to the business users responsible for managing and monitoring the processes. BPMN 2.0 has evolved to become a complete specification trying to fit the needs to all people involved in the design of a business process. But writing BPMN in XML and visualizing business processes becomes nearly impossible without the use of a graphical tool.

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How to Manage Model Versions

In the following short tutorial I will explain how you can manage multiple versions of a workflow model and how Imixs-Workflow supports multiple model versions in a productive business application.

The Imixs-Model-Management

The Imixs-Workflow engine supports multiple model versions from the same process model. Each time a running process instance is updated, the Imixs-Workflow engine applies the same model version as the process instance was created with. Therefor the Imixs-Workflow engine compares the internal model version with the model versions provided by the model repository. In case the current model version is no longer supported, the active process instance will be automatically upgraded to the latest version available in the repository. With this feature it is possible to manage different versions of the same workflow process. To distinguish different model versions, you need a versioning concept.

Semantic Versioning

The concept of “Semantic Versioning” from Tom Preston-Werner will be the basis for the versioning method of process models. Applying the semantic versioning, the version number is separated into three digits:

  1. 2. 3 
  |  |  |-- patch level
  |  |-------- minor version 
  |-------------- major version

Major Version

The first digit indicates the major version number. This is in our case the general main release of a model.  The major version number should only be increased if a general redesign of  whole the process model was done.

Minor Version

The minor version number is used for new functions and enhancements in the process flow. For example after adding a new task or a new event, the minor version number should be increased.

Patch Level

The last digit is used for the Patch Level of a model. It indicates bug fixes or changes of naming or wording.

The semantic versioning can be perfectly used for the BPMN model file. This helps you to manage different version within your modellng tool:

invoicing-1.0.0.bpmn

We typically prefix the filename with the process name to maintain different workflows in the same directory.  In the example above we have an Invoicing workflow in the version 1.0.0. The model file itself should also be stored in a code repository like Git. This allows you to remove deprecated models from your code base.

The Model Version

Also the Imixs-Workflow Model holds a separate version number. This version number is mandatory and can be maintained in the Workflow Profile of the Imixs-BPMN modeling tool:

We prefix the version number again with the process name followed by a two-digit version number. Applied to the “Semantic Versioning” only the Major and Minor Version number is used here!

The reason for this shorter version number is, that the model repository of a business application should not hold different patch levels of the same model. Remember, the patch level is only used to  indicates bug fixes or changes of naming or wording. Only if the model is extended functional the minor version number is increased or in case of a new process variant the major version number:

Modelversion    File Version            Comment 
----------------------------------------------------------   
invocing-1.0    invocing-1.0.0.bpmn     First draft
                invocing-1.0.1.bpmn     typo
invocing-1.1    invocing-1.1.0.bpmn     additional approval
                invocing-1.1.1.bpmn     change mail message
                invocing-1.1.2.bpmn     change history text
invocing-2.0    invocing-2.0.0.bpmn     new Invoicing process

In this example version 1.0 of the Invoicing process was first patch with a typo and next extended with an additional approval, which leads to Minor version 1.1. In this version again then some text changes were made. And finally a complete new Invoicing process was designed, with leads to the new Major version 2.0.

From the view of the running process instances only 3 different model versions exist. From the view of the code repository the model file exists in 6 different versions.

Conclusion

With the concept of “Semantic Versioning” process models can be easily handled in different versions. Even if you need to patch an already running model, you don’t need to worry about polluting the model repository of your business application if you use only 2 digits for internal model version.

How to Model Business Rules?

Today, when you design a modern business application, you have to deal more and more with constantly changing business rules. The reason for this is that not only the software industry follows the agile path. Business processes are also subject to a permanent change. At the same time, however, business processes are becoming increasingly complex as more and more information is influencing our business world. In the following I will show how business processes and their rules can be modeled with the help of BPMN.

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Imixs-BPMN for Eclipse Oxygen

With the new version 1.8, Imixs-BPMN is now available for all current Eclipse platforms and also fully integrated into the latest version of Eclipse Oxygen.

Imixs-BPMN in  based on the Open Source BPMN modelling tooling for Eclipse Oxygen, which is currently available in version 1.4.3. See the Eclipse BPMN Homepage for what’s new. The current version 1.8 of Imixs-BPMN can be installed from here.

Imixs-BPMN takes the full advantage of all the capabilities from the BPMN 2.0 standard and complements them with the requirements to a modern workflow management system. Imixs-BPMN enhances the Eclipse BPMN2 modelling Framework with the aspects of a human-centric workflow model executable on the Imixs-Workflow Engine.

The Imixs-Workflow engine provides a set of modern Java Enterprise Services to create and manage process instances based on a BPMN 2.0 definition. The Imixs-Workflow engine can be embedded into a Java Enterprise application as well be deployed into a Microservice Architecture as a Docker Container. See the Imixs-Microservice Project for more details.

Also for older versions of the Eclipse Platforms (Eclipse Mars, Eclipse Neon) Imixs-BPMN is still are available.

Imixs-BPMN – Version 1.4.7 Released

The open source project Imixs-BPMN has released version 1.4.7. Besides the integration into the Eclipse platform Oxygen, the new version offers various improvements in modeling business processes based on the BPMN 2.0 standard.

Imixs Workflow is a human centric workflow engine that allows to model and to execute human-2-human business processes. Based on the Eclipse platform, Imixs-BPMN offers a professional and stable platform for modeling within the BPMN 2.0 standard. Both, responsibilities and access rights, as well as individual business rules can be modelled graphically.

Version 1.4.7 now represents business rules – so called ‘ conditions ‘ – and access rights (ACL) in a graphical way. This makes it easier to create process models and control them during the design phase.

In addition, Imixs-BPMN now supports so-called ‘Conditional-Events’ and ‘Split-Events’. The former can be used to model decisions based on business rules. Split-Events support parallelism. Split-Events play an important role for the mapping of audit-safe business processes. These new features increase the transparency of complex processes within an organisation.

Imixs-BPMN is open source and part of the Imixs-Workflow technology. The IMIXS Software Solutions GmbH supports enterprises and organisations in the development and implementation of digital business processes.

Imixs-BPMN – Data Objects

With the latest version 4.2.5, the Imixs-Workflow Engine, is now supporting BPMN Data Objects. This kind of model element can be used to model more complex wokflows processing input data:

With this new feature any kind of data object – e.g. a XML or HTML templates – can be associated with a BPMN Task. As a result, the task element will provide these data objects in the new item ‘dataObject’. This item can be injected into a running process instance. See the following code example which is injecting a ‘Invoice HTML template’ into a workitem:

...
ItemCollection task = model.getTask(1000);
List<List<String>> dataObjects = task.getItemValue("dataObjects");
if (dataObjects.size()>0) {
    List<String> firstDataObject = (List<String>) dataObjects.get(0);
    String templateName = firstDataObject.get(0);
    String content = firstDataObject.get(1);
    logger.info("DataObject name=" + templateName);
    logger.info("DataObject content=" + content);
  }
  if ("Invoice Template".equals(templateName) {
    // inject data...
    workitem.repalceItemValue("htmldocument",content);
  }
}
....

DataObjects are part of Imixs-Office-Workflow Version 3.2  to provide an easy and flexible way to create documents and templates during a business process.

BPMN 2.0 – Conditional Events

With version 4.2.0 the Imixs-Workflow engine supports conditional events. A conditional event can be defined with one of the BPMN Gateways  ExclusiveInclusive or EventBased.

Conditional Events

The conditions are defined as boolean rule expressions for each output of the gateway. A condition can be defined with the Script language JavaScript. The following example evaluates the workitem attribute ‘_budget’ for a value greater than 100:

(workitem._budget && workitem._budget[0]>100)

With Conditional Events, Imixs-BPMN offers a significant extension of the modeling possibilities for BPMN 2.0 models to be executed within the Imixs-Workflow engine. Find further details about the modelling with Imixs-BPMN here.