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Facts

Let’s define the data structure for storing facts. Facts are the basic building block for storing data. If we make sure that input, intermediate and output data is always structured the same, it facilitates creating processing pipeline that click together easily.

We’ll split storing data for facts into two parts:

  • The term, which is the “meat” of the data.
  • The info, which is the metadata

Next, those parts are explained further.

Term: core information

When dealing with rules, we want our data to be chunked in meaningful objects, containing the information you actually care about.

For example, we want to define a person that consists of a name and an age.

A term

In our terminology, we’ll say that the term person has two fields. A field has a key (the name of the variable) and an actual value. In JSON notation, this looks as follows:

person = {
  "name": "Bart",
  "age": 10
}

An address can be another term, with fields street, house_number, city etc.

Those simple objects are commonly referred to domain objects, model objects, (named) tuples or terms. We use the latter, “Term”, to denote a defined part from the domain of discourse.

The keys of a term, could in theory be anything, but for mental comfort we’ll limit them to lower cased names, possibly separated by an underscore ( _ ).

note

Note that we don’t assume any validity checking on fields at this stage, such (dis)allowing missing data, or formats in which dates should be written. Later on, you can use rules to check if terms are valid.

Info: Meta data

The meta data, or simply called info here, is in a way of secondary importance.

Meta data

The actual data is the term, but for example:

  • the source of a term (is this person data coming from social media, an address book, a government API?)
  • the date this data was created
  • what previous rules provided this data, for tracing back how this person is processed in the rule engine.

The latter shows how info can be used by the rule engine for certain bookkeeping.

Like terms, info is organized in key-value pairs.

Facts: Terms with meta data

Facts will form the unit of individual data points, for the remaining discussion of the system, since it is the combination of “normal” data (the term) and meta data (the info), and therefore contains all we need.

A fact