ASPECT Language

ASPECT is declarative sub-language of ASP that can be used to define the graphical representation of an answer set. ASPECT (standard) syntax consists of 21 special atomic formulas that define rendering of geometric primitives such as points, lines, polygons, ellipses, etc. The positioning of each element is determined by Cartesian coordinates.

The syntax of the ASPECT language is inspired by the popular PGF/TikZ language developed for drawing vector graphics in the markup language LaTeX.

A concise variant of the ASPECT language has been developed specifically for graph visualization (these are called graph atoms). This variant allows the user to define graphical elements (e.g., nodes and edges) without the need to worry about specifying coordinates, which are instead handled and optimized by the TikZ package. This variant consist of 6 atoms.

Attention

The following two sets of ASPECT atoms (standard atoms and graph atoms) are incompatible so they cannot be used in the same ASP program at the same time.

Animated graphics

For certain problem types, each answer set represents a sequence of actions to be executed in order to achieve a goal starting from a defined initial state. In these problems, dynamic visualization through animation is especially valuable, providing insights into the transition from the initial state to the final state. In this regard, each atom in the ASPECT language supports an optional integer argument denoted by frame which represents the frame of the animation in which the graphical element should be inserted.

Hint

ASPECT atoms without the frame parameter will be inserted in all frames of the animation.

Standard Drawing Atoms

Graphic element	ASPECT atoms
node	aspect_drawnode(x1,y1,text,[attributes],[frame]) aspect_imagenode(x1,y1,image,[attributes],[frame])	x1 x-coordinate y1 y-coordinate text set the node label image path of image attributes (opt.) attributes list frame (opt.) frame number

• text: quoted or unquoted text. If text contains whitespaces or special characters, quotation marks are mandatory.

• image: the file path to the image.

• attributes: (optional) a single attribute, or a tuple (att1, att2, …). See ASPECT attributes for details.

• frame: (optional) integer number representing the frame of the animation in which the graphical element should be inserted.

line	aspect_line(x1,y1,x2,y2,[attributes],[frame]) x1 start point x-coordinate y1 start point y-coordinate x2 end point x-coordinate y2 end point y-coordinate attributes (opt.) attributes list frame (opt.) frame number
arc	aspect_arc(x1,y1,a1,a2,r1,[attributes],[frame]) x1 x-coordinate of the center y1 y-coordinate of the center a1 start angle a2 end angle r1 radius attributes (opt.) attributes list frame (opt.) frame number
straight arrow	aspect_arrow(x1,y1,x2,y2,[attributes],[frame]) x1 tail x-coordinate y1 tail y-coordinate x2 tip x-coordinate y2 tip y-coordinate attributes (opt.) attributes list frame (opt.) frame number
square / rectangle	aspect_rectangle(x1,y1,x2,y2,[attributes],[frame]) x1 first corner x-coordinate y1 first corner y-coordinate x2 second corner x-coord y2 second corner y-coord attributes (opt.) attributes list frame (opt.) frame number
triangle	aspect_triangle(x1,y1,x2,y2,x3,y3,[attributes],[frame]) x1 first vertex x-coordinate y1 first vertex y-coordinate x2 second vertex x-coord y2 second vertex y-coord x3 third vertex x-coord y3 third vertex y-coord attributes (opt.) attributes list frame (opt.) frame number
circle	aspect_circle(x1,y1,r1,[attributes],[frame]) x1 center x-coordinate y1 center y-coordinate r1 radius attributes (opt.) attributes list frame (opt.) frame number
ellipse	aspect_ellipse(x1,y1,r1,r2,[attributes],[frame]) x1 center x-coordinate y1 center y-coordinate r1 x radius r2 y radius attributes (opt.) attributes list frame (opt.) frame number

Graph Drawing Atoms

Attention

The two sets of ASPECT atoms (standard atoms and graph atoms) are incompatible so they cannot be used in the same ASP program at the same time.

Graphic element	ASPECT atoms	Parameters description
node	aspect_graphdrawnode(A,[shape],[frame]) aspect_graphcolornode(A,fill,[shape],[frame])	A node label (name) shape (opt.) node shape fill sets fill color

• shape: allows to choose the circle shape for the node. By default nodes are represented by squares.

Hint

• aspect_graphdrawnode(1) a square-shaped node.

• aspect_graphdrawnode(2, circle) a circular-shaped node.

edge	aspect_graphdrawline(A,B,[frame]) aspect_graphquoteline(A,B,text,[frame])	A name first endpoint B name second endpoint text sets edge label
arrow	aspect_graphdrawarrow(A,B,[frame]) aspect_graphquotearrow(A,B,text,[frame])	A name arrow tail B name arrow tip text sets edge label

• text: quoted or unquoted text. If text contains whitespaces or special characters, quotation marks are mandatory.