Detailed architecture

MES Connector

The MES Connector connects to the Work Tasks server during configuration and at run time. During configuration, the MES Connector connects to the Work Tasks server to:

• Retrieve workflow repository information

• Provision the workflow repository for the MES middleware

• Create the MES User Provider for MES users to access Enterprise Console

At run time (after a workflow repository is connected from the Work Tasks Connector Configuration tool), the MES Connector connects to the Work Tasks server to:

• Raise workflow events

• Execute GetDS and SendXMLCmd methods

• Get stored procedure schema using the Schema Discovery service

• Get MES user information

User Authentication for Connections

Communication between Work Tasks and the MES middleware is handled using the Windows communication service. These connections are secured using Windows authentication.

To call the WCF service hosted on the Work Tasks server, the client (MES middleware) requires valid Windows authentication user information for the Work Tasks server. The same applies to the WCF service hosted on the MES Middleware server.

There is a second level of authorization for access to the workflow repository available on the Work Tasks server under a Work Tasks farm. Only a user who has administrator rights in the workflow repository can make a connection to the MES Connector service and access workflow repository-specific information.

Schema Discovery Service

The Schema Discovery service uses a plug-in infrastructure to retrieve schema information for the Stateless APIs provided by MES. The plug-in is loaded from the folder \Workflow\SPSchema\PlugIn in the installed MES application folder. The schema information is primarily used in workflow design time and run time to allow workflow users to view and access the data shared by the MES middleware. The schema files are categorized as:

• CmdSchema: Input parameters for the stored procedure.

• DSSchema: Data returned as a dataset.

• OutputSchema: Output parameters for the stored procedure.

Most of the Stateless APIs exposed by MES internally call a stored procedure. The MES middleware GetDS and SendXMLCmd methods perform the Stateless API calls. These methods are exposed by the MES middleware WCF service hosted on the MES Middleware server. The data passed to these methods follow an XML structure. Mapping this structure as XML variables in a workflow allows users to access and also use and view the data within workflows more effectively.

MSMQ

Microsoft Message Queuing is used for reliable event delivery.

The workflow events triggered from MES middleware extensibility hooks are sent via MSMQ to the MES Connector service hosted on the MES Middleware server. The Windows service delivers these events to the Work Tasks server. MSMQ ensures that the events are not lost if the MES middleware shuts down or the MES Connector service crashes.

MES Middleware Extensibility Hooks

Hooks are infrastructures provided by the MES middleware to intercept Stateless API calls made on the MES middleware by GetDS and SendXMLCmd calls. The Stateless API calls to the MES middleware internally run a specific stored procedure. Adding a hook in turn allows custom code to be executed in the MES middleware. This code can be executed to perform custom steps before or after the stored procedure execution.

Workflow event generation based on pre- and post-stored procedure execution are handled through the hooks. This integration allows a workflow to be triggered based on a Stateless API call from the MES middleware client.