PROJECTOR manual page
Table of Contents

Name

projector - semi-composition and generation of Labelled Transition Systems

Synopsis

bcg_open [bcg_opt] spec[.bcg] [cc_opt] projector [projector_opt] interface[.bcg] result[.bcg]

or:

exp.open [exp_opt] spec[.exp] [cc_opt] projector [projector_opt] interface[.bcg] result[.bcg]

or:

fsp.open [fsp_opt] spec[.lts] [cc_opt] projector [projector_opt] interface[.bcg] result[.bcg]

or:

lnt.open [lnt_opt] spec[.lnt] [cc_opt] projector [projector_opt] interface[.bcg] result[.bcg]

or:

lotos.open [lotos_opt] spec[.lotos] [cc_opt] projector [projector_opt] interface[.bcg] result[.bcg]

or:

seq.open [seq_opt] spec[.seq] [cc_opt] projector [projector_opt] interface[.bcg] result[.bcg]

Description

projector takes two different inputs:

projector performs the semi-composition of spec with respect to the LTS interface and using a synchronization set determined by the -sync option.

The resulting LTS is stored in result, in BCG format.

The semantics of the semi-composition operator is given in $CADP/doc/*/Krimm-Mounier-97.* and in Section FORMAL DEFINITION OF SEMI-COMPOSITION below.

In a few words, projector reduces the LTS spec by suppressing the transitions that are not possible when spec is synchronized with interface, with respect to a given synchronization set (see -sync option below). The way transitions are suppressed depends on the nature of the interface. See option -userinterface for details.

Options

bcg_opt
if any, are passed to bcg_lib .

exp_opt
if any, are passed to exp.open .

fsp_opt
if any, are passed to fsp.open .

lnt_opt
if any, are passed to lnt.open .

lotos_opt
if any, are passed to caesar and caesar.adt .

seq_opt
if any, are passed to seq.open .

cc_opt
if any, are passed to the C compiler.

The following options projector_opt are currently available:

-monitor
Open a window for monitoring in real-time the generation of result.bcg. This is not a default option.

-sync [-total|-partial|-gate] sync-file
Use the synchronization rules defined in sync-file. The -total, -partial, and -gate options specify the "total matching", "partial matching", and "gate matching" semantics, respectively.

In "total matching" semantics, the regular expressions contained in sync-file denote full labels (i.e., gates possibly followed by experiment offers). Each transition of spec carrying a label that matches some rule in sync-file must be synchronized with a transition of interface carrying the same label.

In "partial matching" semantics, the regular expressions contained in sync-file denote substrings of labels. Each transition of spec carrying a label, a substring of which matches some rule in sync-file, must be synchronized with a transition of interface carrying the same label.

At last, in "gate matching" semantics, the regular expressions contained in sync-file denote gates. Each transition of spec carrying a label, the first word of which (called gate) matches some rule in sync-file, must be synchronized with a transition of interface carrying the same label. In this case, regular expressions in the synchronization set should not contain characters forbidden in gate identifiers (e.g., " ", "(", or "!").

Option -total is the default.

-hide [ -total | -partial | -gate ] hiding_filename
Use the hiding rules defined in hiding_filename to hide (on the fly) the labels of the LTS being generated. See the caesar_hide_1 manual page for a detailed description of the appropriate format for hiding_filename.

The -total, -partial, and -gate options specify the "total matching", "partial matching", and "gate matching" semantics, respectively. See the caesar_hide_1 manual page for more details about these semantics. Option -total is the default.

Note that label hiding does not operate on spec, but on the LTS resulting from the semi-composition of spec with respect to interface.bcg.

-rename [-total|-single|-multiple|-gate] renaming_filename
Use the renaming rules defined in renaming_filename to rename (on the fly) the labels of the LTS being generated. See the caesar_rename_1 manual page for a detailed description of the appropriate format for renaming_filename.

The -total, -single, -multiple, and -gate options specify the "total matching", "single partial matching", "multiple partial matching", and "gate matching" semantics, respectively. See the caesar_rename_1 manual page for more details about these semantics. Option -total is the default.

As for the bcg_labels tool, several hiding and/or renaming options can be present on the command-line, in which case they are processed from left to right. However, the semi-composition (synchronizations) is always performed before hiding and/or renaming. Note that hiding and renaming only affect the part of refused labels that follow the "fail: " string.

Note that label renaming does not operate on spec, but on the LTS resulting from the semi-composition of spec with respect to interface.bcg.

-userinterface | -interfaceuser
This option is used when interface is a "user-given" interface, in which case projector computes validation predicate in the form of refused transitions, in order to check the validity of this interface. A refused transition is identified by its label, which begins with the string "fail: ". Such a label may be present in spec, but not in interface. When -userinterface is specified, projector may produce new refused transitions in addition to those already existing in spec. Note that this option does not make sense outside an entire compositional generation process and it is mainly used by the svl tool. The validation predicates are checked by the exp.open tool, with -interfaceuser option. This is not a default option.

-uncompress, -compress, -register, -short, -medium, -size
These options control the form under which the BCG graph result.bcg is generated. See the bcg manual page for a description of these options.

-tmp
This option specifies the directory in which temporary files are to be stored. See the bcg manual page for a description of this option.

Projector Usage

Even if projector may be used by the command line described in the SYNOPSIS section, it is mainly used by svl with svl script lines like: 

"spec.lotos" -|| "interface.bcg"
"spec.lotos" -|[G1, G2]| "interface.bcg"

Format for Input Labelled Transition Systems

The LTS expressed by spec does not have any restriction. In particular, it may contain refused transitions (i.e., labels prefixed by the special marker "fail: ").

The LTS contained in interface may not contain refused transitions. No other constraint is imposed (for instance, it may have non deterministic transitions).

Note: Minimizing interface for safety equivalence after hiding all labels that are not accepted by the synchronization set is likely to improve the time and space performances of projector, while not changing the resulting LTS. In svl, those two operations are automatically performed before calling projector.

Format for Output Labelled Transition System

The resulting LTS (result[.bcg]) may contain refused transitions. Such refused transitions form a loop from one state to the same state with a label prefixed by "fail: ".

Format for Synchronization Sets

The description of the synchronization set is made through a file, which must respect the following grammar: 
<sync-set>        ::=  <positive-header> '\n' <label-list>
                   |   <negative-header> '\n' <label-list>
<label-list>      ::=  <label>
                   |   <label> '\n' <label-list>
<label>           ::=  <regexp-denoting-a-label>
<positive-header> ::=  'Sync' 
                   |   'sync'
<negative-header> ::=  'Sync all but'
                   |   'sync all but'

If the header is a positive header, any label matching a regular expression of the file will be considered as accepted by the synchronization set. On the contrary, if the header is a negative header, any label that does not match any regular expression of the file will be considered as accepted by the synchronization set. The synchronization set should not accept any label prefixed by "fail: " if there is any in the graph module. The special label "i" should not be accepted by the synchronization set. If it does, a warning is issued but "i" is not synchronized. When no synchronisation set is given, the synchronisation is performed on all labels of spec and interface, except the hidden label "i".

Formal Definition of Semi-composition

First of all, remind that an LTS is defined formally as a tuple (Q, A, T, q0), where Q is the set of states, A is a set of actions, T is the transition relation between states, and q0 is the initial state.

Let S1 and S2 be two LTSs, and SYNC be a set of labels (the synchronization set). We write (S1 |[SYNC]| S2) the parallel composition of S1 and S2, using an extension of LOTOS parallel composition, where SYNC contains full labels instead of gates.

The semi-composition (S1 -|[SYNC]| S2) is the LTS (Q, A, T, q0) defined as follows:

Frequently Asked Questions About Semi-composition

In the sequel, we describe LTSs as sets of transitions of the form q -a-> q'. The initial state will be generally noted q0, and sets of states and actions can be easily reconstructed from the transition relation.

Q:
Does (S1 -|[SYNC]| S2) have always less states and transitions than S1?

A:
Yes. One can see from the mathematical definition that (S1 -|[SYNC]| S2) cannot have more than the states and transitions of S1.

Q:
If LTS S1 is minimal modulo an equivalence relation (e.g., strong, branching, etc.), will (S1 -|[SYNC]| S2) be also a minimal LTS?

A:
No, as shows the following example. Take the minimal LTS S1 = {q0 -a-> q1, q0 -a-> q2, q1 -b-> q3}. The semi-composition (S1 -|[b]| S2), where S2 contains a unique state and no transition, results in {q0 -a-> q1, q0 -a-> q2}, which is not minimal (q1 and q2 are equivalent states).

Q:
Starting from an LTS S1, I made the following two experiments: (1) simply minimize S1; (2) first restrict S1 by semi-composition and then minimize the result. Amazingly the LTS obtained by experiment (2) was larger than that obtained by experiment (1). Is this normal?

A:
Yes, this may happen, for instance, if semi-composition breaks some symmetry in S1. Take S1 = {q0 -a-> q1, q1 -a-> q2, q2 -a-> q0}. Experiment (1), i.e., minimizing S1 yields S2 = {q0 -a-> q0}. Experiment (2) using (S1 -|[a]| S3) with S3 = {q0 -a-> q1, q1 -a-> q2} yields S3, which is minimal. S3 is effectively larger than S2.

Q:
Are standard equivalence relations congruences for the semi-composition operator.

A:
No. Take LTSs S1, S2, and S3 defined in previous example. S1 and S2 are equivalent, but (S1 -|[a]| S3) (which is equal to S3) is not equivalent to (S2 -|[a]| S3) (which is equal to S2). However, most equivalence relations (strong, branching, observational, tau*.a, safety) are semi-congruences for semi-composition, in the sense that minimizing the interface will not alter the result of semi-composition.

Exit Status

Exit status is 0 if everything is alright, 1 otherwise.

Diagnostics

When the source is erroneous, error messages are issued.

Bibliography

Authors

Version 1.x of projector was developped by Jean-Pierre Krimm using an algorithm written by Laurent Mounier and himself (VERIMAG).

Version 2.x of projector was totally rewritten from scratch by Gordon Pace, Bruno Ondet, Nicolas Descoubes, and Frederic Lang (INRIA Rhone-Alpes/VASY).

Version 3.x of projector was partially rewritten by Remi Herilier and Frederic Lang (INRIA Rhone-Alpes/VASY).

Operands

spec.bcg
BCG graph (input)

spec.exp
network of communicating LTSs (input)

spec.lts
FSP specification (input)

spec.lnt
LNT specification (input)

spec.lotos
LOTOS specification (input)

spec.seq
sequence file (input)

interface.bcg
interface LTS (input)

sync-file.sync
set of synchronization labels (input)

result.bcg
BCG graph (output)

Files

The binary code of projector is available in $CADP/bin.`arch`/projector.a

See Also

CAESAR Reference Manual, OPEN/CAESAR Reference Manual, bcg , bcg_open , caesar_hide_1 , caesar_rename_1 , caesar , caesar.adt , exp , exp.open , fsp.open , lnt.open , lotos , lotos.open , seq , seq.open , svl

Additional information is available from the CADP Web page located at http://cadp.inria.fr

Directives for installation are given in files $CADP/INSTALLATION_*.

Recent changes and improvements to this software are reported and commented in file $CADP/HISTORY.

Bugs

Please report new bugs to cadp@inria.fr

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