As an open source rule engine and product suite, Drools is well suited for the small and middle scale business to manage and integrate the rules to build the rule-driven system which can process the business-critical data and events to produce the automated decision. It is better to use Drools in the well-secured environment (back-end behind the DMZ), not putting it on the customer-facing front or exposing it directly the to public where may bring direct security risk in the enterprise environment. Drools still needs a lot hardening on the security side.
BizTalk is well suited as middleware. Where you wish to translate an input file into an output file and send it to some endpoint. In our case, we used it to convert and send files to SAP. In many ways, it very flexible, and you can do almost anything you want with it. In many ways, it's a better solution than your SAP XI or PI as middleware, since it's much less expensive, and allows you do interface with non-SAP systems.
It is very user friendly. Users can change rules during run time and change workflow.
Huge capacity for queueing messages. It supports all types of adapters like Oracle, Salesforce, SMTP, FTP, etc. Also users can built custom adaptors.
If users want to dynamically deploy their solution without any downtime, this is a perfect solution. BizTalk will be a good fit, especially for public-facing websites.
Well-proven in the market. I used it when developing a website for Virgin Trains, catering more than 800K user requests per day.
Fusion doesn't support persistence of working memory, which brings some extra high availability risk to our business.
Guvnor still has a lot room to be implemented, it is not so user-friendly for non-technical people, so a lot of business users complain it is hard to master.
Rule execution server doesn't even have JMX implemented, hard to be monitored.
Drools is still lacking support for key Web services standards.
BizTalk Server has been supported for more than 15 years. It is well proven in the market. Microsoft has provided excellent support with technical issues.
BizTalk was selected here mainly because it is easy to integrate to a .NET application (most of them are Web Service, WCF SOAP, WCF REST and Web API) and many backend databases are Microsoft SQL Server. Another benefit is that the monitoring job is easy to set up and centralize with other .NET application monitoring jobs.
The IT department quickly adopted Drools as it is a very good java-based rule engine, which saves a lot of time to meet the project timeline and balanced our business requirements.
Recently we start considering the OpenRules, which may be more business user-friendly.
A positive impact has been the quicker turnaround time of a part request and that part showing up in SAP using Biztalk as middleware.
A somewhat negative impact has been the somewhat insufficient error logging/message capture settings that Biztalk provide. This has caused occasional delays when attempted to create parts for the business.
A somewhat negative impact has been the need to have a specialized developer who understands Biztalk to troubleshoot issues with the Biztalk and SAP interaction when creating parts, and when adding new fields to the parts.
