parsee-case-eval.md

ParSEE case study: overall evaluation of a decoder (on XML codec's example)

This example shows How ParSEE can be used:

• by the decoder author: to quickly evaluate if it is performing as expected
• by a person unfamiliar with the decoder but wanting to extend it: to see what each rule is doing

Watch the following GIF closely as I oversee rules one by one. Pay attention to:

• areas of input matched by each rule
• color overlapping of the matches

In this short session we have discovered:

• input is valid, as evidenced by the top level rule being green in the end and consuming all of it
• input areas matched by each rule, e.g. STag, ETag, CharData, S*, S+ and so on: good way to spot unexpected or missed matches
• rules element and content are recursive, with former including the latter plus tags
• Name, Attribute, AttValue rules are performing duplicate matching as evidenced by twice repeated patterns in rule profiles
• EmptyElemTag inside element being the most likely culprit of the duplicate matching, as it performs full match and then fails and discards the result at the very end (more general cause usually is the direct translation of EBNF grammer to Parse dialect)