src/main/java/com/bazaarvoice/jackson/rison/IdentifierUtils.java
public static boolean isIdStrict(char[] chars, int offset, int len) {
        if (len == 0) {
            return false;
        }
        int end = offset + len;
        if (!isIdStartStrict(chars[offset++])) {
            return false;
        }
        while (offset < end) {
            if (!isIdCharStrict(chars[offset++])) {
                return false;
            }
        }
        return true;
    }
public static boolean isIdStrict(char[] chars, int offset, int len) {
        if (len == 0) {
            return false;
        }
        int end = offset + len;
        if (!isIdStartStrict(chars[offset++])) {
            return false;
        }
        while (offset < end) {
            if (!isIdCharStrict(chars[offset++])) {
                return false;
            }
        }
        return true;
    }
Returns true if the string represented by the specified character array does not
Uses the strict definition described in the Rison specification, appropriate for encoding.