I was pondering the source= attribute of att.editLike[1] when I
decided to check what Wikipedia says about a sigil. (I wanted to know
if a sigil was something that might serve as a pointer to a witness,
which is what the value description implies.) Interestingly (to me)
the term "sigil" as defined by Wikipedia is primarily an abbreviation
of sorts, and only secondarily involved with "indicating the location
of a source manuscript".

But my point is that in the external links section of the Wikipedia
entry[2], the "XML Specifications for the use of sigla" links to the
TEI P4 chapter on critical apparatus. At the very least this should
be P5, no? But moreover, should there be some indication that the
word "sigil" is used in TEI primarily as a manuscript locator (an
abbreviation for the entire manuscript, as it were :-)?

I do not feel qualified to update the Wikipedia entry myself, but
thought someone here might.

Notes
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[1] http://www.tei-c.org/release/doc/tei-p5-doc/html/ref-att.editLike.html
[2] http://en.wikipedia.org/wiki/Sigla#External_links