Logic language

This page about the logic language from ShapeLogic 0.9 and forward.

For a broader introduction to the logic system see Declarative logic .

Different types of declarative programming in ShapeLogic

  1. Lazy calculations
  2. Lazy streams
  3. IoC, Inversion of Control using Google Guise, not been started yet

Declarative programming concept

  • Lazy computations was expanded
  • Lazy streams was introduced
  • Lazy streams can use the Java 6 Scripting interface
  • Tested with Groovy, JRuby and JavaScript, but this is supporting 25 languages
  • Lazy streams work with matching several polygons at once
  • Named lazy stream turned out to be very easy for user defined rules
  • Using a scripting language is less essential for rule definition is less essential than with goal driven tasks

IoC hold potential but has not been used yet.

Future plan for declarative programming in ShapeLogic

Make menu items in ImageJ's menu for opening and running a user defined rule database, without user defined Java code. Since it was so easy to define rules in Java this have been given lower priority than originally planned.

Problem with Java 6 Scripting for rule definition in ImageJ

One possible problem with moving rules to Java 6 Scripting, is that this requires that the user downloads engine interface files from Sun. This would make the installation of ShapeLogic more complicated now it is just unpacking a zip and moving it into ImageJ's plugin dir.

The only scripting language that works out of the box is JavaScript. While that is a reasonable language the integration with Java is not so great especially not Java 5.

It is also possible to connect Groovy and Java outside Java 6 Scripting, but then it would not be uniform.

Logic expressions syntax in lazy stream approach

DigitStreamVectorizer is an example showing what is needed to define a match of the numbers working as a plugin from ImageJ.

Define a rule for matching the letter A

rule("A", POINT_COUNT, "==", 5.);
rule("A", HOLE_COUNT, "==", 1.);
rule("A", T_JUNCTION_LEFT_POINT_COUNT,"==", 1.);
rule("A", T_JUNCTION_RIGHT_POINT_COUNT,"==", 1.);
rule("A", END_POINT_BOTTOM_POINT_COUNT, "==", 2.);
rule("A", HORIZONTAL_LINE_COUNT, "==", 1.);
rule("A", VERTICAL_LINE_COUNT, "==", 0.);
rule("A", END_POINT_COUNT, "==", 2.);
rule("A", SOFT_POINT_COUNT, "==", 0.);

The "A" is saying apply this rule to the OH, object hypothesis, the letter A.

The next is just names of streams that generate the point count and hole count for the polygons. Then there is the predicate and the comparison value.

Idea behind lazy streams

Lazy streams have the following features

  • You can define a lazy stream based on other lazy streams
  • They works as a kind of UNIX pipes or Legos
  • They serves as your query construct, you can directly query them