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1. Document preparation ###

• Remote provers from SystemOnTPTP (notably for Sledgehammer) are now managed via Isabelle/Scala instead of perl; the dependency on libwww-perl has been eliminated (notably on Linux). Rare INCOMPATIBILITY: HTTP proxy configuration now works via JVM properties https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/net/doc-files/net-properties.html

1. Document preparation ###

• Timeouts for Isabelle/ML tools are subject to system option timeout_scale --- this already used for the overall session build process before, and allows to adapt to slow machines. The underlying Timeout.apply in Isabelle/ML treats an original timeout specification 0 as no timeout; before it meant immediate timeout. Rare INCOMPATIBILITY in boundary cases.

• External bash processes are always managed by Isabelle/Scala, in contrast to Isabelle2021 where this was only done for macOS on Apple Silicon.

1. Isabelle/jEdit Prover IDE ###

1. Isabelle/jEdit Prover IDE ###

• The command-line tool isabelle log prints prover messages from the build database of the given session, following the the order of theory sources, instead of erratic parallel evaluation. Consequently, the session log file is restricted to system messages of the overall build process, and thus becomes more informative.

The official Isabelle2021 release is scheduled for February 2021. This blog entry is dynamically updated to follow the sequence of public release candidates. See also the workboard and the isabelle-release repository.

1. Document preparation ###

• The command-line tool isabelle build provides option -P DIR to produce PDF/HTML presentation in the specified directory; -P: refers to the standard directory according to ISABELLE_BROWSER_INFO / ISABELLE_BROWSER_INFO_SYSTEM settings. Generated PDF documents are taken from the build database -- from this or earlier builds with option document=pdf.

• Experimental support for arm64-linux platform. The reference platform is Raspberry Pi 4 with 8 GB RAM running Pi OS (64 bit).

• Update/rebuild external provers on currently supported OS platforms, notably E prover 2.5, SPASS 3.8ds, CSDP 6.1.1.

• An updated version of the veriT solver is now included as Isabelle component. It can be used in the smt proof method via smt (verit) or via declare [[smt_solver = verit]] in the context; see also session HOL-Word-SMT_Examples.

1. Document preparation ###

The next anticipated release is Isabelle2021 (February 2021). The hot phase with release candidates will presumably be 28-Dec-2020 .. 15-Feb-2020.

• Nitpick/Kodkod may be invoked directly within the running Isabelle/Scala session (instead of an external Java process): this improves reactivity and saves resources. This experimental feature is guarded by system option kodkod_scala (default: false).

• Isabelle server allows user-defined commands via isabelle_scala_service.

• The shell function isabelle_directory (within etc/settings of components) augments the list of special directories for persistent symbolic path names. This improves portability of heap images and session databases. It used to be hard-wired for Isabelle + AFP, but other projects may now participate on equal terms.

1. Isabelle/jEdit Prover IDE ###

• ML statistics via an external Poly/ML process: this allows monitoring the runtime system while the ML program sleeps.

• Theory_Data extend operation is obsolete and needs to be the identity function; merge should be conservative and not reset to the empty value. Subtle INCOMPATIBILITY and change of semantics (due to Theory.join_theory from Isabelle2020). Special extend/merge behaviour at the begin of a new theory can be achieved via Theory.at_begin.

• System option "pide_session" is enabled by default, notably for standard "isabelle build": it allows to invoke Isabelle/Scala operations from Isabelle/ML. Big build jobs (e.g. AFP) require extra heap space for the java process, e.g. like this in $ISABELLE_HOME_USER/etc/settings:

1. Isabelle/jEdit Prover IDE ###

1. Document preparation ###

• Isabelle/Phabricator setup has been updated to follow ongoing development: libphutil has been discontinued. Minor INCOMPATIBILITY: existing server installations should remove libphutil from /usr/local/bin/isabelle-phabricator-upgrade and each installation root directory (e.g. /var/www/phabricator-vcs/libphutil).

• The command-line tool "isabelle sessions" explores the structure of Isabelle sessions and prints result names in topological order (on stdout).

• The command-line tool isabelle build_docker has been slightly improved: it is now properly documented in the system manual.

• Mixfix annotations may use "' " (single quote followed by space) to separate delimiters (as documented in the isar-ref manual), without requiring an auxiliary empty block. A literal single quote needs to be escaped properly. Minor INCOMPATIBILITY.

1. Isabelle/jEdit Prover IDE ###

1. Isabelle/jEdit Prover IDE ###

The official Isabelle2020 release is scheduled for April 2020. This blog entry is dynamically updated to follow the sequence of public release candidates.

• The command-line tool "isabelle scala_project" creates a Gradle project configuration for Isabelle/Scala/jEdit, to support Scala IDEs such as IntelliJ IDEA.

The next anticipated release is Isabelle2020 (April 2020). The hot phase with release candidates will presumably be 01-Mar-2020 .. 15-Apr-2020.

• The command-line tool "isabelle hg_setup" simplifies the setup of Mercurial repositories, with hosting via Phabricator or SSH file server access.

• The command-line tool "isabelle phabricator_setup" facilitates self-hosting of the Phabricator software-development platform, with support for Git, Mercurial, Subversion repositories. This helps to avoid monoculture and to escape the gravity of centralized version control by Github and/or Bitbucket. For further documentation, see chapter "Phabricator server administration" in the "system" manual. A notable example installation is https://isabelle-dev.sketis.net/.