Basic concepts of the JANUS user interface

JANUS was designed to be programmable. The programming language is Tcl/Tk, expanded by some object classes and their methods. Object classes are things like dictionaries, codebooks, but also the decoder itself is an object class. Every object class has its methods (operations that can be done with objects of that class). Objects can have subobjects and can be hierarchically organized. The object oriented programming paradigm allows, at least in principle, to plug in and out objects as one wishes. Simply change the dictionary by assigning a new one, copy codebooks as easily as "cb1 := cb2", add distribution accumulators as easily as "ds1.accu += ds2.accu", etc.

Create JANUS Objects

Objects are meant to hold data but also provide methods to manipulate that data. To define an object you have to specify its type. The convention is that type names start with capital letters and objects with small letters. You can define as many objects of one type as you like. To see what types exist just type (one of the few) JANUS command 'types'.
By the way '%' is the prompt of the JANUS shell. You can also use any Tcl and Tk commands.

% types FlatFwd ModelArray DurationSet Word Cbcfg SampleSet DVector
PTree HMM AModel Rewrite CodebookSet Vocab FMatrix CodebookMapItem
PTreeSet MLNorm Dscfg PathItemList Question DictWord MLAdaptItem
CodebookAccu HypoList DBaseIdx SampleSetClass SenoneTag Feature
QuestionSet Dictionary DBase Lm PhonesSet DCovMatrix Phone FBMatrix
Phones DistribAccu IMatrix TreeNode Distrib MLAdapt List Tag TopoSet
SVector XWModel IArray DMatrix FVector StateGraph FCovMatrix
XWModelSet PathItem FArray Duration PTreeNode LatNode Hypo Senone
TreeFwd LDA Topo MLNormClass SenoneSet Lattice WordGraph Codebook Tags
LDAClass FeatureSet Tree PhoneGraph CodebookMap Path TmSet
DistribStream DistribSet Search AModelSet RewriteSet

The list you get here depends on the version and compile options. You create an object when you enter a type name followed by the name of the new object. Some types require additional arguments, like subobjects. As an example we define an object (let's call it 'ps') of type PhonesSet. You can get a list of all objects you have defined with the command 'objects'. One object name can only be used once (also for different types) but you can 'destroy' objects. 'destroy' is a standard method of every object (s.b.).

% PhonesSet ps
ps
% PhonesSet ps
WARNING itf.c(0287)   Object ps already exists.
% PhonesSet ps2 
ps2
% objects
ps ps2

summary: JANUS commands
types	list all object types
objects	list all objects defined by user

Methods

Standard Methods

As soon as you have defined an object you can use its name followed by a method and arguments. The different object types have their own methods of course but at least a few are standard methods that exist for every object. These are

standard methods
type	give the type of the object
puts	print contents of the object
configure	configure the object
:	allow access to list element
.	allow access to subobjects
destroy	destroy object

To find out what other methods exist we enter eather the type name without any object name or the object name follwed by '-help'. To get more information about a specific method we enter the object name, the method and '-help'.

% ps -help

DESCRIPTION

A 'PhonesSet' object is a set of 'Phones' objects.

METHODS

puts               displays the contents of a set of phone-sets
add                add new phone-set to a set of phones-set
delete             delete phone-set(s) from a set of phone-sets
read               read a set of phone-sets from a file
write              write a set of phone-sets into a file
index              return index of named phone-set(s)
name               return the name of indexed phone-set(s)

% ps add -help
Options of 'add' are:
 < name>    name of list (string:"NULL")
 < phone*>  list of phones
% ps add VOWEL A E I O U

We just added the element 'VOWEL' to the PhonesSet object ps. To see the contents of the object we can use the method 'puts' or just the object name which is the same in most cases.

% ps puts 
VOWEL
% ps
VOWEL

Access to Elements and Subobjects

The standard methods ':' and '.' allow access to elements and subobjects respectively. Elements of an object have the same kind of structure, like the words of a dictionary, or phone groups (like the 'VOWEL') in the PhonesSet. Nevertheless, they can also be objects and most of the time they are. Subobjects are more unique, like the Phones of a dictionary as we will see immediately. For these two methods and only for them you can omit the spaces between the object and also between the single argument which is the name of the element or the subobject. If you don't give a name you will obtain a list of the choices.
In case of ':' you again get a list of the elements like with 'puts' or just the object name with no method.

% ps:
VOWEL
% ps:VOWEL
A E I O U
% ps type
PhonesSet
% ps:VOWEL type
Phones

Let's assume we have also defined a phone group 'PHONES' in the PhonesSet 'ps' that contains all the Phones of a dictionary. Then we can create a dictionary object that needs the name of a Phones object and of a Tags object as arguments. Both have to be created first.

% Tags ts
ts
% Dictionary d ps:PHONES ts
d
% d add DOG "D O G"
% d add DUCK "D U CK"
% d.
phones tags item(0..1) list
% d:
DOG DUCK

With 'd.phones', for example, you have access to the object 'ps:PHONES'. Although there is a method for PhonesSet to delete elements like 'PHONES' you will get an error if you try that because it was locked as you defined the dictionary. This prevents objects from being deleted while they are being used by other objects.

Configuration

Sometimes it might be necessary to configure objects or object types. You can get all configure items or get a specific one, or set one or more items, although only if they are writable.

% ps configure
{-useN 1} {-commentChar {;}} {-itemN 2} {-blkSize 20} 
% ps configure -commentChar
{;}
% ps configure -commentChar #

Note: The old comment sign ';' was protected with curly braces {} because it is the command separator in Tcl.

Question: Can you explain the following line and its return value.

% ps configure -commentChar ;
#

Maintainer: maier@ira.uka.de