ShapeLogic has a declarative goal driven logic engine.
So the context makes it possible to have the string "Letter" bound to both "A" and "B" at the same time in difference context. The context set up as a hierarchy, like in most programming languages. So names that I bound in a higher context can be seen in a lower one.
This rely on [http://commons.apache.org/jexl/ Java Expression Language (JEXL)]
ShapeLogic is driven by a tree of tasks. The super class is called BaseTask.
A task can have sub tasks, but also have a context that inherits from the context of the parent task. But not all tasks have their own context.
For example of simple rules and task hierarchy look in the classes
At the top level of the tree there is an Exclusive or task, XOrTask. Under there there is an AndTask for each letter. For each AndTask there are several simple property rules, called
Each AndTask have its own context that values can be set in, but all the SimpleTask under an AndTask share a context. When a letter finally is chosen then the context from the chosen context is propagated up.
So the vectorizer will put a MultiLinePolygon object into the string "polygon" in a JEXL context.
Then there are rules that go in and look at the object using reflection. Here is an example of a simple NumericRule:
NumericRule("A", "pointCount", "polygon.getPoints().size()", 5.),Here is an example of all the rules for a letter:
NumericRule[] numericRulesForA = {
new NumericRule("A", POINT_COUNT, POINT_COUNT_EX, 5.),
new NumericRule("A", LINE_COUNT, LINE_COUNT_EX, 5.),
new NumericRule("A", HORIZONTAL_LINE_COUNT, HORIZONTAL_LINE_COUNT_EX, 1.),
new NumericRule("A", VERTICAL_LINE_COUNT, VERTICAL_LINE_COUNT_EX, 0.),
new NumericRule("A", END_POINT_COUNT, END_POINT_COUNT_EX, 2.),where
POINT_COUNT = "pointCount"; POINT_COUNT_EX = "polygon.getPoints().size()"
All these rules are combined into and AndTask. A whole letter match will then be an XOrTask with an AndTask for each letter.
If you need to do more complex boolean combinations of filter on polygons try the following:
"polygon.filter('PointRightOfFilter(0.3) && PointAboveFilter(0.3)')"
"polygon.filter('PointOfTypeFilter(PointType.T_JUNCTION) && PointLeftOfFilter(0.5)').size()"Currently ShapeLogic is using the standard Java, C, C++ notation:
And use && Or use || Not use !
Prolog was all the rage in the early 1980, the Japanese 5 generation project was mainly based on Prolog. It turned out that it did not scale well to real world problems. Partly because it was only good at handling symbolic information and not doing computations. So Prolog fell out of favor.
I still think programming in Prolog is almost as simple as programming in SQL.
So ShapeLogic is trying to preserve this simplicity of Prolog, while maintaining ability to do efficient numerical calculation.
ShapeLogic is not using backtracking or unification. 2 of the main components in Prolog. But the idea of a program as:
Unlike Prolog ShapeLogic can have multiple values for a name at the same time, and exploring different choices at the same time.
Oz is a experimental language boasting:
The way ShapeLogic is merging contexts when faced with different options is similar to what Oz did. This is currently not fully implemented.