Practices for allowing systems to accommodate human error?_问答_开发者

Systems have to sometimes accommodate the possibility of real world bad data. Consider that s开发者_如何学Goome data originates with paper forms. And forms inherently have a limited means of validating data.

Example 1: On one form users are expected to enter an integer distance (in miles) into a blank. We capture the information as written as a string since we don't always end up getting integer values.

Example 2: On another form we capture a code. That code should map to one of the codes in our system. However, sometimes the code written on the form is incorrect. We capture the code and allow it to exist with an invalid value until some future time of resolution. That is, we temporarily allow bad data since it's important to record the record even if some of it is invalid.

I'm interested in learning more about how systems accommodate bad data, that is, human error. Databases are supposed to be bastions of data integrity, but the real world is messy and people make mistakes. Systems must allow us to reflect those mistakes.

What are some ways systems you've developed accommodate human error? What practices have you used? What lessons have you learned?

Any further reading on the topic? (I had trouble Googling it.)

I agree with you, whatever we do there's no guarantee that we can get rid of bad or incorrect data. Especially, but not only, if it comes to user input. In my experience the same problems exist in complex integration projects, in which you have to integrate and merge (often inconsistent) data retrieved from different systems.

A good strategy is to decouple the input from the operational system itself. First, place user (or external system) provided data in a separate datastore (e.g. different schema). In a second step load this data into your operational datastore, but only if it confirms to strict rules (e.g. use address verification software to verify a given address). This Extract, Transform, Load (ETL) approach is fairly common in Data Warehousing (DWH) solutions, but can be applied programmatically in transactional systems as well (in my experience).

The above approach often leads to asynchronous processes in which the input is subitted first and (maybe) at a later time the external entity (user or system) retrives feedback whether its data was correct or not.

EDIT: For further readings I recommend to have a look at DWH concepts. Alhtough, you may not want to build such a thing, you could partially apply those concepts:

http://en.wikipedia.org/wiki/Extract,_transform,_load

http://en.wikipedia.org/wiki/Data_warehouse

http://en.wikipedia.org/wiki/Data_cleansing

A government department I worked in does a lot of surveys, most of which are (were) still paper based.

All the results were OCR'd into the system.
As part of the OCR process a digital scan of the forms is kept.
Data is then validated, data that is undecipherable or which fails validation is flagged.
When a human operator reviews the digital data they can modify the data if they are confident that they can correctly interpret what the code could not; they (here's the cool bit) can also bring up the scan of the paper based original, and use that to determine what the user was trying to say.

On a different thread; at some point you want to validate the data coming in against any expected data ranges that you want it to conform to; buy rejecting it at the point of entry you give the user a chance to correct it - the trade off is that every time you reject it you increase the chance of them abandoning the whole process.

At some point in your system you need to specify the rules which will be used for validation. At the end of the day a system is only going to be as smart as those rules. You can develop these yourself into the code (probably the business logic) or you might use a 3rd party component.

having flexible control over the validation is pretty important as they are likely to change overtime.

To be honest with you, one point of migrating from paper-based systems to IT is to remove these errors and make sure all data is always correct. I doubt any correctly planned and developed IT system (especially business financial systems) would allow such errors. Not in the company I am working for anyway...

There are lots of software tools that address the kinds of problems you mention. There are platforms and tools that let you define rules for scrubbing and transforming data and handling validation errors. Those techniques are widely used for Data Integration and Business Intelligence applications. Google for "Data Quality" or "Data Integration".

The easiest thing to do is to (this is not always possible) design the interface where users enter the data to limit as much as possible the amount of text that they need to enter. In my experience this seems to be where a lot of problems come from. One simple example of this is to provide a select, or auto-complete select field

One thing that you could do is do everything possible to determine if the data is correct before going into the db. I try to give the user entering the data as much feedback as possible so they can (ideally) fix some of the issues before the data gets persisted. For example, it is a very quick check to determine if the data being entered is of the correct type.

I got started in legal systems before the PC era. Litigation support databases routinely have to accommodate factually incorrect, incomplete, and contradictory information. It takes a different way of thinking.

The short version . . .

Instead of recording a single fact, you record multiple assertions about a fact. It boils down to designing a database to store data from assertions like these.

In an interview at 2011-01-03 08:13, Neil Rimes told Officer Cane that he was at home from 2011-01-02 20:00 until 2011-01-03 08:13.
In an interview at 2011-01-03 08:25, Liza Nevers told Officer Cane that Neil Rimes came home at 2011-01-02 23:45.
In a deposition at 2011-05-13 10:22, Cody Maxon told attorney Kurt Schlagel that he saw Neil Rimes at Kroger at 2011-01-03 03:00