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+++ b/src/Doc/IsarImplementation/Integration.thy Tue Aug 28 18:57:32 2012 +0200
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+theory Integration
+imports Base
+begin
+
+chapter {* System integration *}
+
+section {* Isar toplevel \label{sec:isar-toplevel} *}
+
+text {* The Isar toplevel may be considered the central hub of the
+ Isabelle/Isar system, where all key components and sub-systems are
+ integrated into a single read-eval-print loop of Isar commands,
+ which also incorporates the underlying ML compiler.
+
+ Isabelle/Isar departs from the original ``LCF system architecture''
+ where ML was really The Meta Language for defining theories and
+ conducting proofs. Instead, ML now only serves as the
+ implementation language for the system (and user extensions), while
+ the specific Isar toplevel supports the concepts of theory and proof
+ development natively. This includes the graph structure of theories
+ and the block structure of proofs, support for unlimited undo,
+ facilities for tracing, debugging, timing, profiling etc.
+
+ \medskip The toplevel maintains an implicit state, which is
+ transformed by a sequence of transitions -- either interactively or
+ in batch-mode. In interactive mode, Isar state transitions are
+ encapsulated as safe transactions, such that both failure and undo
+ are handled conveniently without destroying the underlying draft
+ theory (cf.~\secref{sec:context-theory}). In batch mode,
+ transitions operate in a linear (destructive) fashion, such that
+ error conditions abort the present attempt to construct a theory or
+ proof altogether.
+
+ The toplevel state is a disjoint sum of empty @{text toplevel}, or
+ @{text theory}, or @{text proof}. On entering the main Isar loop we
+ start with an empty toplevel. A theory is commenced by giving a
+ @{text \<THEORY>} header; within a theory we may issue theory
+ commands such as @{text \<DEFINITION>}, or state a @{text
+ \<THEOREM>} to be proven. Now we are within a proof state, with a
+ rich collection of Isar proof commands for structured proof
+ composition, or unstructured proof scripts. When the proof is
+ concluded we get back to the theory, which is then updated by
+ storing the resulting fact. Further theory declarations or theorem
+ statements with proofs may follow, until we eventually conclude the
+ theory development by issuing @{text \<END>}. The resulting theory
+ is then stored within the theory database and we are back to the
+ empty toplevel.
+
+ In addition to these proper state transformations, there are also
+ some diagnostic commands for peeking at the toplevel state without
+ modifying it (e.g.\ \isakeyword{thm}, \isakeyword{term},
+ \isakeyword{print-cases}).
+*}
+
+text %mlref {*
+ \begin{mldecls}
+ @{index_ML_type Toplevel.state} \\
+ @{index_ML Toplevel.UNDEF: "exn"} \\
+ @{index_ML Toplevel.is_toplevel: "Toplevel.state -> bool"} \\
+ @{index_ML Toplevel.theory_of: "Toplevel.state -> theory"} \\
+ @{index_ML Toplevel.proof_of: "Toplevel.state -> Proof.state"} \\
+ @{index_ML Toplevel.debug: "bool Unsynchronized.ref"} \\
+ @{index_ML Toplevel.timing: "bool Unsynchronized.ref"} \\
+ @{index_ML Toplevel.profiling: "int Unsynchronized.ref"} \\
+ \end{mldecls}
+
+ \begin{description}
+
+ \item Type @{ML_type Toplevel.state} represents Isar toplevel
+ states, which are normally manipulated through the concept of
+ toplevel transitions only (\secref{sec:toplevel-transition}). Also
+ note that a raw toplevel state is subject to the same linearity
+ restrictions as a theory context (cf.~\secref{sec:context-theory}).
+
+ \item @{ML Toplevel.UNDEF} is raised for undefined toplevel
+ operations. Many operations work only partially for certain cases,
+ since @{ML_type Toplevel.state} is a sum type.
+
+ \item @{ML Toplevel.is_toplevel}~@{text "state"} checks for an empty
+ toplevel state.
+
+ \item @{ML Toplevel.theory_of}~@{text "state"} selects the
+ background theory of @{text "state"}, raises @{ML Toplevel.UNDEF}
+ for an empty toplevel state.
+
+ \item @{ML Toplevel.proof_of}~@{text "state"} selects the Isar proof
+ state if available, otherwise raises @{ML Toplevel.UNDEF}.
+
+ \item @{ML "Toplevel.debug := true"} makes the toplevel print further
+ details about internal error conditions, exceptions being raised
+ etc.
+
+ \item @{ML "Toplevel.timing := true"} makes the toplevel print timing
+ information for each Isar command being executed.
+
+ \item @{ML Toplevel.profiling}~@{ML_text ":="}~@{text "n"} controls
+ low-level profiling of the underlying ML runtime system. For
+ Poly/ML, @{text "n = 1"} means time and @{text "n = 2"} space
+ profiling.
+
+ \end{description}
+*}
+
+text %mlantiq {*
+ \begin{matharray}{rcl}
+ @{ML_antiquotation_def "Isar.state"} & : & @{text ML_antiquotation} \\
+ \end{matharray}
+
+ \begin{description}
+
+ \item @{text "@{Isar.state}"} refers to Isar toplevel state at that
+ point --- as abstract value.
+
+ This only works for diagnostic ML commands, such as @{command
+ ML_val} or @{command ML_command}.
+
+ \end{description}
+*}
+
+
+subsection {* Toplevel transitions \label{sec:toplevel-transition} *}
+
+text {*
+ An Isar toplevel transition consists of a partial function on the
+ toplevel state, with additional information for diagnostics and
+ error reporting: there are fields for command name, source position,
+ optional source text, as well as flags for interactive-only commands
+ (which issue a warning in batch-mode), printing of result state,
+ etc.
+
+ The operational part is represented as the sequential union of a
+ list of partial functions, which are tried in turn until the first
+ one succeeds. This acts like an outer case-expression for various
+ alternative state transitions. For example, \isakeyword{qed} works
+ differently for a local proofs vs.\ the global ending of the main
+ proof.
+
+ Toplevel transitions are composed via transition transformers.
+ Internally, Isar commands are put together from an empty transition
+ extended by name and source position. It is then left to the
+ individual command parser to turn the given concrete syntax into a
+ suitable transition transformer that adjoins actual operations on a
+ theory or proof state etc.
+*}
+
+text %mlref {*
+ \begin{mldecls}
+ @{index_ML Toplevel.print: "Toplevel.transition -> Toplevel.transition"} \\
+ @{index_ML Toplevel.no_timing: "Toplevel.transition -> Toplevel.transition"} \\
+ @{index_ML Toplevel.keep: "(Toplevel.state -> unit) ->
+ Toplevel.transition -> Toplevel.transition"} \\
+ @{index_ML Toplevel.theory: "(theory -> theory) ->
+ Toplevel.transition -> Toplevel.transition"} \\
+ @{index_ML Toplevel.theory_to_proof: "(theory -> Proof.state) ->
+ Toplevel.transition -> Toplevel.transition"} \\
+ @{index_ML Toplevel.proof: "(Proof.state -> Proof.state) ->
+ Toplevel.transition -> Toplevel.transition"} \\
+ @{index_ML Toplevel.proofs: "(Proof.state -> Proof.state Seq.seq) ->
+ Toplevel.transition -> Toplevel.transition"} \\
+ @{index_ML Toplevel.end_proof: "(bool -> Proof.state -> Proof.context) ->
+ Toplevel.transition -> Toplevel.transition"} \\
+ \end{mldecls}
+
+ \begin{description}
+
+ \item @{ML Toplevel.print}~@{text "tr"} sets the print flag, which
+ causes the toplevel loop to echo the result state (in interactive
+ mode).
+
+ \item @{ML Toplevel.no_timing}~@{text "tr"} indicates that the
+ transition should never show timing information, e.g.\ because it is
+ a diagnostic command.
+
+ \item @{ML Toplevel.keep}~@{text "tr"} adjoins a diagnostic
+ function.
+
+ \item @{ML Toplevel.theory}~@{text "tr"} adjoins a theory
+ transformer.
+
+ \item @{ML Toplevel.theory_to_proof}~@{text "tr"} adjoins a global
+ goal function, which turns a theory into a proof state. The theory
+ may be changed before entering the proof; the generic Isar goal
+ setup includes an argument that specifies how to apply the proven
+ result to the theory, when the proof is finished.
+
+ \item @{ML Toplevel.proof}~@{text "tr"} adjoins a deterministic
+ proof command, with a singleton result.
+
+ \item @{ML Toplevel.proofs}~@{text "tr"} adjoins a general proof
+ command, with zero or more result states (represented as a lazy
+ list).
+
+ \item @{ML Toplevel.end_proof}~@{text "tr"} adjoins a concluding
+ proof command, that returns the resulting theory, after storing the
+ resulting facts in the context etc.
+
+ \end{description}
+*}
+
+
+section {* Theory database \label{sec:theory-database} *}
+
+text {*
+ The theory database maintains a collection of theories, together
+ with some administrative information about their original sources,
+ which are held in an external store (i.e.\ some directory within the
+ regular file system).
+
+ The theory database is organized as a directed acyclic graph;
+ entries are referenced by theory name. Although some additional
+ interfaces allow to include a directory specification as well, this
+ is only a hint to the underlying theory loader. The internal theory
+ name space is flat!
+
+ Theory @{text A} is associated with the main theory file @{text
+ A}\verb,.thy,, which needs to be accessible through the theory
+ loader path. Any number of additional ML source files may be
+ associated with each theory, by declaring these dependencies in the
+ theory header as @{text \<USES>}, and loading them consecutively
+ within the theory context. The system keeps track of incoming ML
+ sources and associates them with the current theory.
+
+ The basic internal actions of the theory database are @{text
+ "update"} and @{text "remove"}:
+
+ \begin{itemize}
+
+ \item @{text "update A"} introduces a link of @{text "A"} with a
+ @{text "theory"} value of the same name; it asserts that the theory
+ sources are now consistent with that value;
+
+ \item @{text "remove A"} deletes entry @{text "A"} from the theory
+ database.
+
+ \end{itemize}
+
+ These actions are propagated to sub- or super-graphs of a theory
+ entry as expected, in order to preserve global consistency of the
+ state of all loaded theories with the sources of the external store.
+ This implies certain causalities between actions: @{text "update"}
+ or @{text "remove"} of an entry will @{text "remove"} all
+ descendants.
+
+ \medskip There are separate user-level interfaces to operate on the
+ theory database directly or indirectly. The primitive actions then
+ just happen automatically while working with the system. In
+ particular, processing a theory header @{text "\<THEORY> A
+ \<IMPORTS> B\<^sub>1 \<dots> B\<^sub>n \<BEGIN>"} ensures that the
+ sub-graph of the collective imports @{text "B\<^sub>1 \<dots> B\<^sub>n"}
+ is up-to-date, too. Earlier theories are reloaded as required, with
+ @{text update} actions proceeding in topological order according to
+ theory dependencies. There may be also a wave of implied @{text
+ remove} actions for derived theory nodes until a stable situation
+ is achieved eventually.
+*}
+
+text %mlref {*
+ \begin{mldecls}
+ @{index_ML use_thy: "string -> unit"} \\
+ @{index_ML use_thys: "string list -> unit"} \\
+ @{index_ML Thy_Info.get_theory: "string -> theory"} \\
+ @{index_ML Thy_Info.remove_thy: "string -> unit"} \\[1ex]
+ @{index_ML Thy_Info.register_thy: "theory -> unit"} \\[1ex]
+ @{ML_text "datatype action = Update | Remove"} \\
+ @{index_ML Thy_Info.add_hook: "(Thy_Info.action -> string -> unit) -> unit"} \\
+ \end{mldecls}
+
+ \begin{description}
+
+ \item @{ML use_thy}~@{text A} ensures that theory @{text A} is fully
+ up-to-date wrt.\ the external file store, reloading outdated
+ ancestors as required. In batch mode, the simultaneous @{ML
+ use_thys} should be used exclusively.
+
+ \item @{ML use_thys} is similar to @{ML use_thy}, but handles
+ several theories simultaneously. Thus it acts like processing the
+ import header of a theory, without performing the merge of the
+ result. By loading a whole sub-graph of theories like that, the
+ intrinsic parallelism can be exploited by the system, to speedup
+ loading.
+
+ \item @{ML Thy_Info.get_theory}~@{text A} retrieves the theory value
+ presently associated with name @{text A}. Note that the result
+ might be outdated.
+
+ \item @{ML Thy_Info.remove_thy}~@{text A} deletes theory @{text A} and all
+ descendants from the theory database.
+
+ \item @{ML Thy_Info.register_thy}~@{text "text thy"} registers an
+ existing theory value with the theory loader database and updates
+ source version information according to the current file-system
+ state.
+
+ \item @{ML "Thy_Info.add_hook"}~@{text f} registers function @{text
+ f} as a hook for theory database actions. The function will be
+ invoked with the action and theory name being involved; thus derived
+ actions may be performed in associated system components, e.g.\
+ maintaining the state of an editor for the theory sources.
+
+ The kind and order of actions occurring in practice depends both on
+ user interactions and the internal process of resolving theory
+ imports. Hooks should not rely on a particular policy here! Any
+ exceptions raised by the hook are ignored.
+
+ \end{description}
+*}
+
+end