A set of rules for the encoding of classical epigraphic and papyrological texts using simple, arbitrary and unambiguous symbols to represent editorial observations and interventions, e.g. '[' and ']' for lost text (restored or lacuna). There are several minor variations on Leiden now in use (Krummrey-Panciera and PETRAE perhaps prominent among them). A good summary of Leiden can be found at en.wikipedia.org/wiki/Leiden_Conventions
Leiden+ is a system of text markup, based very closely on Leiden but including new signs and combinations for complex apparatus markup, for example, devised for the Papyrological Editor's "tags-free" editing environment. Full description and documentation of Leiden+ is at papyri.info/editor/help.
The Morpheus morphological analysis service is a tool originally developed by Perseus, versions of which are in use by Papyri.info and the TLG for lemmatizing their Greek texts. The Perseus version of the tool also caters for Latin and Arabic lemmatization. [Reference page for Morphological Analysis Service]
Extensible Markup Language. A text-based encoding format that allows the structured encoding of text or data in human- and machine-readable format. It is the technical basis of both TEI and EpiDoc, and is a standard maintained by the World-wide Web Consortium. See www.w3.org/XML for the spec and further description.