SharePoint 2013: workflows overview

Introduction
Workflows is one of the most used functionalities in SharePoint and can be applied in almost any type of company. SharePoint 2010 didn't offer many different things compared to SharePoint 2007. Both were based on the Workflow foundation 3.5 framework.
SharePoint 2010 did introduce site based workflows running in the site context, you could create reusable workflows, import them in a Visual Studio 2010 coded workflow, create reusable workflows with SharePoint designer and some workflow events were introduced.

In SharePoint 2013, workflows from SharePoint 2010 are still going to run and you can still build workflows using the old methods. In the new version, a workflow is treated as a service and runs in an on-premise and a hosted model. Everything is now based on Windows Azure Workflow. These workflows run in the context of the Windows Azure Workflow and not in the SharePoint process.

High level architecture

When you publish a workflow to SharePoint 2013, it's going to store a copy (the master version) of the workflow and will then push it to Windows Azure Workflow where it will run.

When a workflow is started, SharePoint 2013 is going to tell Windows Azure Workflow (WAW) which workflow needs to run and will also provide it with information like on which list item the workflow was launched and in which site it needs to run. WAW will then queue the job and run it when possible. If extra information is needed, WAW will communicate to SharePoint using the CSOM via WCF to get the necessary details.

Workflows based on WFD 4.0 can only be built of your current farm is connected to a WAW environment.

Improvements

• Stages: provides support for repeating and skipping workflow steps. A stage is a combinations of workflow activities. After a stage is completed a new stage can start. This next stage is not necessarily the next stage in the schema. A stage has a 'goto' action. A stage can be connected to any other stage.
• Loops: SharePoint Designer 2013 now supports loops.
• We can call web services. The result of this call can be stored in workflow variables and used further on.
• Programmatic workflows are still possible but only in WAW. It's recommended to use web services when custom logic is needed.
• New tools: SharePoint Designer and Visual Studio.