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Introduction
Why Ampersand?
Tutorial
Reactive programming
The language Ampersand
How to read syntax statements
Truth
Atoms
The CONCEPT statement
The RELATION statement
The MEANING statement
The PURPOSE statement
The CLASSIFY statement
The RULE statement
Terms
Context
Module
Best Practices
Syntactical Conventions
The INCLUDE statement
Patterns
Services
Population
The ENFORCE statement
The IDENT statement
The TABLE statement
Language support
Current date
The Preprocessor
Design considerations
Running the Ampersand compiler
Architecture of an Ampersand Application
Deploying your Ampersand script
Reusing Available Modules
Exercises
Installing Ampersand
Modeling
Configuring your application
The Excel Importer
Plans
Research
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Truth
An information system should represent the truth. So, as a designer you must know a thing or two about truth.
Let us introduce some language to talk about truth. Consider a fact "Joe Smith lives in New York." from an Ampersand perspective. In Ampersand, we can analyse this as follows:
  • Let Person and City be concepts****
  • Let "Joe Smith" be an atom of the concept Person and "New York" an atom of the concept City.
  • Let us use the relation livesIn[Person*City] to contain our fact.
  • livesIn is the relation name and [Person*City] is the signature of this relation.
  • Person is the source of this relation and City is the target.
  • If the pair ("Joe Smith","New York") is an element of this relation, Ampersand considers the statement "Joe Smith" livesIn "New York" to be true. So all pairs in a relation represent facts, i.e. true statements.

Language that makes sense to the business

Ampersand takes a pragmatic stance on truth: You model only things that make sense to the business. This video clip illustrates the distinction between sensible and senseless statements. A sensible statement (we say: "It makes sense.") is a statement that can be true or false. Sentences that are not sensible (we can say: it is non-sense) are to be avoided. The Ampersand type system helps you to make sensible statements only.

Truth in context

Truth always has context. If we say "Jack was married to Jackie", this statement is true in a context where "Jack" refers to the 35th president of the United States, John F. Kennedy. However, this statement is not true in a context where there is no Jack. And in a context where marriage doesn't exist, this statement makes no sense.
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Language that makes sense to the business
Truth in context