5 ms·

Am I missing something or is this just another rules engine?

perlgeek 12y ago
Did you dismiss twitter with the same line? Twitter is also just another rules engine, with pretty simple rules about which tweets you receive. And yet it's also so much more. It's a platform, and it's a social network. And it's something that many people love to use. Who cares if it's just another rules engine under the hood?
- pestaa 12y ago
  Not only that, but the interface is always a huge part of any product that's simple under the hood, and I'm going to check it out and evaluate right now...
- psaintla 12y ago
  Twitter isn't really a rules engine as it doesn't have the ability to create workflows or manage rule priority afaik but let's ignore that for a second. Rules engines are typically a terrible idea and I say this as someone who has worked at two large corporations, one a bank, where rules engines were heavily used so they could avoid having the larger development staff they really needed. Rules engines fail miserably every single time and eventually have to be replaced. The problem is that as time goes on people who don't know any better end up writing larger and more complex rules and workflows without an understanding of the side effects those rules generate. The end result inevitably becomes a huge mess that is extremely fragile and nearly impossible to follow.
  - themoonbus 12y ago
    Yes, but for simple, personal rules that won't have any major repercussions if they fail (e.g. email me when I get 10 likes on my last Instagram photo), I can see how they'd be useful. ...not that my hypothetical rule is useful, but you understand what I'm getting at.
    - psaintla 12y ago
      Absolutely. For simple, isolated, inconsequential tasks this works fine. The problem is rules engines always start very innocent and simple, then users request the ability to have rules call each other, then they want to store results, etc. In an ideal world this is a good thing but I have yet to hear of any place where rules engines, used at any significant scale, aren't a complete disaster.
      - johnobrien1010 12y ago
        Is it typically a disaster because business users are given access to create their own rules and they don't know what they're doing, or because the complexity of the system grows to the point where that complexity is better managed by other tools (version control systems, QA environments, rigorous testing, etc.)?
        psaintla 12y ago
        In my experience, both. It starts with business users creating rules without having a clue what they are doing and it ends with the system becoming so complex that it would have been better off being written by engineers using tools more appropriate for the job. Typically what happens is that business discovers they can now implement every last feature they desire without getting any push back from engineering so they go wild implementing new features without realizing the consequences. There is no VCS, no QA, no testing. There is no one telling them they cannot do something because it won't scale, it isn't secure or it won't be maintainable. Their only metric for success is that they get the result they want now and the long term consequences be damned. Worse yet, every single person using the rules engine is acting independently and not as a team. There is no code review, when the rule works to their satisfaction it gets pushed into production. At first everything works fine and people get promoted for saving money on engineering costs but then the rules start getting more complex, start becoming composed of other rules, need to have more complex actions or need to integrate with third party systems. Eventually the simple rules engine turns into a bastardized programming language that everyone adds onto and never modifies because no one understands how a modification will affect the 4000 other rules in the engine. At that point you end up having to do a complete re-write, which is something I have had the displeasure of doing in the past.

Did you dismiss twitter with the same line? Twitter is also just another rules engine, with pretty simple rules about which tweets you receive. And yet it's also so much more. It's a platform, and it's a social network. And it's something that many people love to use. Who cares if it's just another rules engine under the hood?

pestaa 12y ago
Not only that, but the interface is always a huge part of any product that's simple under the hood, and I'm going to check it out and evaluate right now...
psaintla 12y ago
Twitter isn't really a rules engine as it doesn't have the ability to create workflows or manage rule priority afaik but let's ignore that for a second. Rules engines are typically a terrible idea and I say this as someone who has worked at two large corporations, one a bank, where rules engines were heavily used so they could avoid having the larger development staff they really needed. Rules engines fail miserably every single time and eventually have to be replaced. The problem is that as time goes on people who don't know any better end up writing larger and more complex rules and workflows without an understanding of the side effects those rules generate. The end result inevitably becomes a huge mess that is extremely fragile and nearly impossible to follow.
- themoonbus 12y ago
  Yes, but for simple, personal rules that won't have any major repercussions if they fail (e.g. email me when I get 10 likes on my last Instagram photo), I can see how they'd be useful. ...not that my hypothetical rule is useful, but you understand what I'm getting at.
  - psaintla 12y ago
    Absolutely. For simple, isolated, inconsequential tasks this works fine. The problem is rules engines always start very innocent and simple, then users request the ability to have rules call each other, then they want to store results, etc. In an ideal world this is a good thing but I have yet to hear of any place where rules engines, used at any significant scale, aren't a complete disaster.
    - johnobrien1010 12y ago
      Is it typically a disaster because business users are given access to create their own rules and they don't know what they're doing, or because the complexity of the system grows to the point where that complexity is better managed by other tools (version control systems, QA environments, rigorous testing, etc.)?
      - psaintla 12y ago
        In my experience, both. It starts with business users creating rules without having a clue what they are doing and it ends with the system becoming so complex that it would have been better off being written by engineers using tools more appropriate for the job. Typically what happens is that business discovers they can now implement every last feature they desire without getting any push back from engineering so they go wild implementing new features without realizing the consequences. There is no VCS, no QA, no testing. There is no one telling them they cannot do something because it won't scale, it isn't secure or it won't be maintainable. Their only metric for success is that they get the result they want now and the long term consequences be damned. Worse yet, every single person using the rules engine is acting independently and not as a team. There is no code review, when the rule works to their satisfaction it gets pushed into production. At first everything works fine and people get promoted for saving money on engineering costs but then the rules start getting more complex, start becoming composed of other rules, need to have more complex actions or need to integrate with third party systems. Eventually the simple rules engine turns into a bastardized programming language that everyone adds onto and never modifies because no one understands how a modification will affect the 4000 other rules in the engine. At that point you end up having to do a complete re-write, which is something I have had the displeasure of doing in the past.