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-rw-r--r--doc/external-dependency-solver-protocol.txt15
1 files changed, 10 insertions, 5 deletions
diff --git a/doc/external-dependency-solver-protocol.txt b/doc/external-dependency-solver-protocol.txt
index e2bd95866..d914db309 100644
--- a/doc/external-dependency-solver-protocol.txt
+++ b/doc/external-dependency-solver-protocol.txt
@@ -263,11 +263,11 @@ the user.
#### Solution
-A solution is a list of Deb 822 stanzas. Each of them could be an
-install stanza (telling APT to install a specific package), a remove
-stanza (telling APT to remove one), or an autoremove stanza (telling APT
-about the *future* possibility of removing a package using the
-Autoremove action).
+A solution is a list of Deb 822 stanzas. Each of them could be an install
+stanza (telling APT to install a specific new package or to upgrade or
+downgrade a package to a specific version), a remove stanza (telling APT to
+remove one), or an autoremove stanza (telling APT about the *future*
+possibility of removing a package using the Autoremove action).
An **install stanza** starts with an Install field and supports the
following fields:
@@ -289,6 +289,11 @@ this protocol makes no assumption on the fact that a subsequent
invocation of an Autoremove action will actually remove the very same
packages indicated by Autoremove stanzas in the former solution.
+The package identifiers of install, remove and autoremove stanzas from a single
+solution are unique. That is, a package identifier does not occur more than
+once in the solution. Every package identifier is only associated with a single
+action (either install, remove or autoremove).
+
In terms of expressivity, install and remove stanzas can carry one
single field each, as APT-IDs are enough to pinpoint packages to be
installed/removed. Nonetheless, for protocol readability, it is