SignalArc Applications
Free to use software applications are listed below. These applications should be of particular interest to publishers, but are free to use for any application. They are maintained by Eamonn Neylon, brand owner of SignalArc. Source code for each application is available at the signalarc github repositories.
CREPDL Checker
CREPDL is an important but unfamiliar technology for publishers.
CREPDL·CHECK is an online validation service that checks text against a character repertoire — a defined set of permitted Unicode characters — using the rules of ISO/IEC 19757-7:2020, the international standard for the Character Repertoire Description Language (CREPDL).
In the Unicode era, accepting any Unicode character may lead to problems. Nobody can read all characters, few fonts cover all characters, and some software supports only a subset of Unicode. UTF-8 now exposes almost 88,000 CJK ideographic characters alone. Historically, legacy encodings like Shift JIS implicitly constrained character sets, but UTF-8 removes those guardrails.
CREPDL addresses this directly: a CREPDL schema describes a character repertoire, and a stream of UCS code points can be validated against that schema.