Topological composition systems: specifications for lexical elements of visual languages

• Published in: Proceedings 1991 IEEE Workshop on Visual Languages pp. 118 - 124
• Main Authors: Chow, A.L., Rubin, R.V.
• Format: Conference Proceeding
• Language: English
• Published: IEEE Comput. Soc. Press 1991
• Subjects: Algorithm design and analysis; Computational geometry; Displays; Graphics; Information analysis; Page description languages; Performance analysis; Program processors; Programming environments; Programming profession
• ISBN: 9780818623301; 0818623306
• DOI: 10.1109/WVL.1991.238842

The paper explains the role of lexical analysis in a visual programming environment. The authors classify the visual lexical elements based on the geometric properties of their composition operators. They explore the class of topologically composed lexical elements and provide a method of specifying them. They refer to these specifications as topological composition systems. The core of such a system is a set of composition rules that define the topological compositions to be performed and the conditions when the rules can be fired. They also describe the design of a lexical analyzer for topological composition systems. The design uses efficient computational geometry algorithms to achieve a time complexity of O( mod R mod N log N) for an input size of N primitive picture elements, where mod R mod is the number of rules in the system. A lexical analysis phase, preceding parsing, can reduce the input size to the parser by 30%-50%. Early experiments also show that using topological lexical analysis can enhance the overall picture recognition process performance by a factor of 10.< >