<s5>Æliens</s5> -- slide(s)

Software architecture

architecture -- components and boundaries
case study -- a framework for multimedia feature detection
native objects -- the language boundary
embedded logic -- the paradigm boundary
architectural styles -- distributed object technology
cross-platform development -- Unix versus Windows

Additional keywords and phrases: components, information architecture, multimedia information retrieval, feature detection, portability

slide: Software architecture

Elements of architecture

[Wolf]

processing elements -- transformation on data
data elements -- contain information
connections -- glue that holds elements together

Models and views

[Kruchten95]

logical -- functional requirements
process -- performance, availability, distribution
physical -- scalability, configuration
development -- organization of software modules
scenarios -- instances of use cases

Definitions

www.sei.cmu.edu/architecture/definitions.html

slide: Elements of architecture -- models and views

The software architecture of a program or computing system is the structure of the system, which comprises software components, the externally visible properties of those components, and their interrelationships.

Technological infrastructure

[CS2001]

client-platform -- hardware, OS
presentation services -- windows, multimedia
application software -- code, business logic
network -- communication support
middleware -- distribution, (object) brokers
server platform -- hardware, OS
database -- data management system

slide: Technological infrastucture

Distributed object patterns

[CorbaPatterns]

Framework

(class hierarchies)

Applications

(wrappers)

System

(horizontal, vertical, metadata)

Enterprise

(reference models, infrastructure, policies)

Intra/Internet

(standards)

slide: Distributed object patterns

slide: The extended ACOI architecture


  detector world; // finds the name of the world
  detector people; // checks name, eliminates institutes
  detector company; // looks if there are at least two persons
  
  atom str name;
  
  community: world people company;
  
  world: name;
  people: person*;
  
  person: name;

slide: A sample grammar


  int personDetector(tree *pt, list *tks ){
  ...
  q = query_query("kit=pl src=check.pl");
  
  while (t = next_token(tks)) {
        sprintf(buf,"person(\%s)",t);
        query_eval(q,buf);
        if (query_result(q,0))  put name(person) on tokenstream


                  putAtom(tks,"name",t);
        }
  ...
  }

slide: A person detector


  V0 := newoid();
  V1 := newoid();
    community_world.insert(oid(V0),oid(V1));
      world_name.insert(oid(V1),"casa");
    community_people.insert(oid(V0),oid(V1));
  V2 := newoid();
      people_person.insert(oid(V1),oid(V2));
        person_name.insert(oid(V2),"alice");
      people_person.insert(oid(V1),oid(V2));
        person_name.insert(oid(V2),"sebastiaan");
      ...

slide: Database updates

slide: MIDI features


  
  detector song; ## to get the filename
  detector lyrics; ## extracts lyrics
  detector melody; ## extracts melody
  
  atom str name;
  atom str text;
  atom str note;  
  
  song: file lyrics melody;
  
  file: name;
  lyrics: text*;
  melody: note*;

slide: A simple feature grammar for MIDI files


  event('kortjakje',2,time=384, note_on:[chan=2,pitch=72,vol=111]).
  event('kortjakje',2,time=768, note_off:[chan=2,pitch=72,vol=100]).

slide: Processing MIDI file


  int melodyDetector(tree *pt, list *tks ){
  char buf[1024]; char* _result;
  void* q = _query;
  int idq = 0; 
  
    idq = query_eval(q,"X:melody(X)");
    while ((_result = query_result(q,idq)) ) {
           printf("note: \%s",_result);
           putAtom(tks,"note",_result);
           }
    return SUCCESS;
  }

slide: The melody detector


  given type AtomName, AtomValue;
  
  interface tokenstream {
  	void putAtom(in AtomName, in AtomValue);
  };


  V1 := newoid();
    midi_song.insert(oid(V0),oid(V1));
  V2 := newoid();
      song_file.insert(oid(V1),oid(V2));
        file_name.insert(oid(V2),"kortjakje");
      song_lyrics.insert(oid(V1),oid(V2));
        lyrics_text.insert(oid(V2),"e");
        lyrics_text.insert(oid(V2),"per-");
        lyrics_text.insert(oid(V2),"sonne");
        lyrics_text.insert(oid(V2),"Moi");
        lyrics_text.insert(oid(V2),"je");
        lyrics_text.insert(oid(V2),"dis");
        lyrics_text.insert(oid(V2),"que");
        lyrics_text.insert(oid(V2),"les");
        lyrics_text.insert(oid(V2),"bon-");
        lyrics_text.insert(oid(V2),"bons");
        lyrics_text.insert(oid(V2),"Val-");
        lyrics_text.insert(oid(V2),"ent");
      song_melody.insert(oid(V1),oid(V2));
        melody_note.insert(oid(V2),"a-2");
        melody_note.insert(oid(V2),"a-2");
        melody_note.insert(oid(V2),"g-2");
        melody_note.insert(oid(V2),"g-2");
        melody_note.insert(oid(V2),"f-2");
        melody_note.insert(oid(V2),"f-2");
        melody_note.insert(oid(V2),"e-2");
        melody_note.insert(oid(V2),"e-2");
        melody_note.insert(oid(V2),"d-2");
        melody_note.insert(oid(V2),"d-2");
        melody_note.insert(oid(V2),"e-2");
        melody_note.insert(oid(V2),"c-2");

slide: Update of Monet database

slide: Keyboard interface

slide: User Query Processing

subsections:

Embedded logic -- crossing the paradigm boundary
Native objects -- crossing the language boundary
Combining Java and C++

(SG/X)ML-like syntax for queries
logic engine in filter
Note: this is an offline approach
Rationale: only knowledge maintenance

a simple knowledge base: people
some rules: concerning the institute
a query: to collect email adresses

Motivation: e.g the IM&SE Colloquium.

embedded logic


  <query kit=pl src=local.pl cmd=X:email_address(X)>
  <param format=" \%s">
  <param result="">
  <param display="<h4>The query</h4>">
  <param header="<h4>The adresses</h4> <ul>">
  <param footer="</ul>">
  email_address(E) :-
  	person(X),
  	property(X,name:N),
  	property(X,familyname:F),
  	email(X,E),
  	cout(['', N,' ',F,' has email adress ']),
  	cout([ '<a href=mailto:', E, '>', E, '</a>',nl]).
  </query>


  query pl = new query("kit=pl src=remote.pl");    logic.java  
  pl.eval("X:assistant(X)");
  String res = null;
  while ( (res = pl.result()) != null ) {
              System.out.println(" " + res);
              }


     remote.pl  
  :- source('www.cs.vu.nl/~eliens/db/se/people.pl').
  :- source('www.cs.vu.nl/~eliens/db/se/institute.pl').
  :- source('www.cs.vu.nl/~eliens/db/se/property.pl').
  :- source('www.cs.vu.nl/~eliens/db/se/query.pl').

maintaining knowledge is difficult
don't replicate, otherwise ...
so we need to access knowledge from remote sources
and possibly mix remote and local knowledge
Solution: url-enabled consults
Problem: availability of the (VU) server

queries may clash, we need seperate 'engines'
this is static, the next step is dynamic: signed applets
this is research code, not production code

slide: Remarks


  interface query {    query.idl  
  
          void source(in string file);
          long eval(in string cmd);
          string result(in long id);
  
          oneway void halt();
          };

The next step is to distribute knowledge processing
A simple CORBA framework: client and server
Both client and server can be logic-enabled.
The universe is more logical than it appeared at first sight.

slide: Distributed knowledge servers

Look at the debug information

slide: Distributed knowledge processing - example

Look at the debug information

slide: Distributed knowledge processing - example (2)

knowledge management with logic is feasible
has applications in document engineering and ...
embedding is relatively efficient
can be done in multiple ways
corba enabled logic services are possible
true logic is hard to debug

dynamic: signed applets

slide: Conclusions

Many flavors: Sicstus, ...
Modules do not suffice - ...
Requirements: low overhead, natural syntax
Additional requirements: binding with native objects

slide: Objects in Prolog

native bindings are mostly for functions only
Java, however, provides an example
Let's first look at objects in Prolog, and then their possibly native realization

slide: Native Objects

Objects in Prolog

representation -- object(Handler,Class,ID,REF,Ancestors)
object definition -- class_method(This,...)
object invocation -- self(This):method(...)
state variables representation -- value(ID,Key,Value)
state variable access -- var(Key) = Value, Var = value(key)
native binding - native(Handler,Method,Result)

slide: Objects in Prolog

requirements

low overhead, especially when not needed
natural syntax for object clause definitions
support for native objects


  
          midi(This):midi,  // create midi object
          Self = self(This),
          Self:open('a.mid'),
          Self:header(0,1,480),
          Self:track(start),
          Self:melody([48,50,51,53,55]), // c d es f g, minor indeed
          Self:track(end), // end track


     midi  
  :- use(library(midi:[midi,lily,music,process])).
  :- declare(midi:object,class(midi),[handler]). 
  
  midi_midi(This) :- // constructor
          midi(This):handler(H),   // gets Handler from class
          declare(H,new(midi(This)),[],[],_).


   native methods
  midi_read(This,F) :- native(_,This,read(F),_). 
  midi_analyse(This,I,O) :- native(_,This,analyse(I,O),_).
  midi_open(This,F) :- native(_,This,open(F),_).
  midi_header(This,M) :- native(_,This,header(M,0,480),_).
  midi_track(This,X) :- native(_,This,track(X),_).
  midi_tempo(This,X) :- native(_,This,tempo(X),_).
  midi_event(This,D,C,M,T,V) :-
  		      native(_,This,event(D,C,M,T,V),_).


  midi_note(This,D,C,T,V) :- 
          Self = midi(This), // cast to midi
          Self:event(D,C,note_on,T,V),
          Self:event(D,C,note_off,T,V).
  
  midi_melody(This,L) :- self(This):melody(480,1,L,64).
  
  midi_melody(_This,_,_,[],_).
  
  midi_melody(This,D,C,[X|R],V) :-
          Self = self(This),
          Self:note(D,C,X,V),  
          midi_melody(This,D,C,R,V).   // direct invocation

method call - check ID is a REF
declaration - call (native) constructor
mapping creation and method calls -- through native support
native support -- binding: object_handler and query_event
native support -- classes: the usual (hush) hierarchy e.g. obscure and kit

slide: Native Objects in Prolog

generic binding for (pl) kit - with secondary handler dictionary
handler hierarchy -- obscure, handler, event, kit, query
downcall - via smart pointer vm
upcall - via embedded vm in handler

slide: C++ bindings


  class query_object : public kit_object {    kit_object  
  public:
  query_object(kit* q, char* n = "query:object") : kit_object(q,n) { }
  object_handler* _create(query* q, char* n = "query:object") {
          return new query_object(q,n);
          }
  int operator()();
  };


  int kit_object::operator()() {
          event* e = _event;
  
          vm<kit> self(e);  // smart pointer
          string method = e->_method();
  
          if (method == "kit") { // constructor
                  kit* q = new kit(e->arg(1));
                  _register(q);
                  result( reference((void*)q) );
          } else if (method == "eval") {
                  long res = self->eval(e->arg(1));
                  result( itoa(res) );
          } else if (method == "result") {
                  char* res = self->result( atoi(e->arg(1)) );
                  result(res);
          } else { // dispatch up in the hierarchy
                  return handler_object::operator()();
          }
  
          return 0;
          }


   in handler.c
  
  event* handler::dispatch(event* e) {
  _event = e;
  if (_vmp) {
          return ((vm*)_vmp)->dispatch(e);
  } else {
  
           if (e->thekit()) tk = e->thekit(); // AE
  
           int result = this->operator()();
  
           if (result != OK) return 0; // jrvosse
           else return _event;
           }
  }


  template <class T>
  class vm  {    smart pointer class  
  public:
  
  vm(event* e) {
          int p = 0;
          char* id = e->option("ref");
          if (id) {
  		p = atoi(id);
  		}
          _self = (T*) p;
          }
  
  
  virtual inline T* operator->() { return _self; }
  
  private:
  T* _self;
  };

See some more examples pointer.c and pointer.pl.
Objects - in a mix of styles
With native support - similar to hush-java support
key-value transfer of native calls
virtuality, operator overloading, nested calls, native support
now we need concurrency ...
remember query: we do have distribution already

slide: Conclusions

representation if C++ peer: self pointer
object/method function call: native functions
cast self pointer to object: smart vm

slide: Native Objects in Java


  package hush.dv.api;
  
  class obscure {    obscure  
  public int _self; // peer object pointer
  ...
  };


  public class handler extends obscure {    handler  
  
  public static kit tk;
  protected Event _event;
  
  public Event dispatch(event ev) {
  	_event = (Event) ev;
  	operator();
  	return _event;
  	}
  
  public int operator() {
  	...
  	return OK;
  	}
  };


  package hush.dv.api;
  
  public class kit extends handler {    kit  
  
  public kit() { _self = init(); }
  protected kit(int x) { }
  private native int init();
  
  public native void source(String cmd);
  
  public native void eval(String cmd);
  
  public String result() { 
  	String _result = getresult();
  	if (_result.equals("-")) return null;
  	else return _result;
  	}
  
  private native String getresult();
  
  public native void bind(String cmd, handler h);
  
  ...
  };


     kit.c  
  include @lt;hush/hush.h>
  include @lt;hush/java.h>
  include @lt;native/hush_dv_api_kit.h>
  
  #define method(X) Java_hush_dv_api_kit_##X
  JNIEXPORT jint JNICALL method(init)(JNIEnv *env, jobject obj)
  {
    jint result = (jint) kit::_default; // (jint) new kit();
    if (!result) {
  	kit* x = new kit("tk");
  	session::_default->_register(x);
  	result = (jint) x;
  	}
    return result;
  }


  JNIEXPORT jstring JNICALL method(getresult)(JNIEnv *env, jobject obj)
  {
    java_vm vm(env,obj);
    char *s = vm->result();
    if (s) return vm.string(s);
    else return vm.string("-");
  }


  JNIEXPORT void JNICALL method(bind)(JNIEnv *env, jobject obj,
  	       jstring s, jobject o)
  {
    java_vm vm(env,obj);
    java_vm* vmp = new java_vm(env,o,"Handler");
    const char *str = vm.get(s);
    handler* h = new handler();
    session::_default->_register(h);
    h->_vmp = vmp;
    h->_register(vmp);
    vm->bind(str,h);
    vm.release(s, str);
  }

handler::dispatch


  
  event* handler::dispatch(event* e) {
  _event = e;
  if (_vmp) {
          return ((vm*)_vmp)->dispatch(e);
  } else {
  
           int result = this->operator()();
  
           if (result != OK) return 0; 
           else return _event;
           }
  }


  #include <hush/vm.h> 
  #include <jni.h>
  
  template< class T >
  class java_vm : public vm< T > {    java_vm  
  public:
  
  java_vm(JNIEnv* env_, jobject obj_) {
  	_env = env_;
  	_obj = obj_;
  	_self = self();
  	}
  
  ...
  
  
  event* dispatch(event* e) {  java dispatch
  	call("dispatch",(int)e);
  	return e;
  	}
  
  
  T* operator->() { return _self; }
  
  T* self() {
  	jfieldID fid = fieldID("_self","I");
  	return (T*) _env->GetIntField( _obj, fid);
  	}
  
  
  void call(const char* md, int i) { // void (*)(int)
  	jmethodID mid = methodID(md,"(I)V");
  	_env->CallVoidMethod(_obj, mid, i);
  	}
  
  private: 
  JNIEnv* _env;
  jobject _obj;
  T* _self;
  };

subsections:

From technology to style
Case study -- perspectives in visualization

the distributed objects style
the (dynamically) downloadable code style
the mobile objects style

slide: Exchanging perspectives

Rules of thumb -- selecting an architectural style

Dedicated hardware or legacy code

distributed objects

Strategic or secret code

distributed objects

Many users

downloadable code

Periodic updates

downloadable code

Communication and negotiation

mobile objects

slide: Rules of thumb

Cross-platform development

Unix vs NT

open toolkits and standards -- OMG CORBA

Research/GNU

AT&T U/WIN -- Posix for 95/NT
Cygnus -- GNU-win32

Commercial

NuTCracker/MKS -- porting Unix applications to Windows
Wind/U, Mainwin -- porting Windows applications to Unix
Tributary -- developing Unix applications from Windows IDE

slide: Cross-platform development

deploying platform-independent toolkits
porting applications from Unix to Windows
porting applications from Windows to Unix

Elements of architecture

processing elements -- transformation on data
data elements -- contain information
connections -- glue that holds elements together

slide: Section 7.1: Elements of architecture

Case study -- multimedia feature detection

feature grammar -- structure
embedded logic -- rules for recognition
architecture -- multimedia information system

slide: Section 7.2: Case study -- multimedia feature detection

Crossing boundaries

embedded logic -- crossing the paradigm boundary
native objects -- crossing the language boundary
combining Java and C++

slide: Section 7.3: Crossing boundaries

Architectural patterns and styles

technology matrix -- from technology to style
case study -- visualization perspectives

slide: Section 7.4: Architectural patterns and styles

Cross-platform development

from Unix to Windows -- AT&T U/Win, Cygnus GNU-win32
from Windows to Unix -- Wind/U, Mainwin

slide: Section 7.5: Cross-platform development

What are the elements of a software architecture? What role does a software architecture description play in development?
Give a definition of software architecture. Can you think of alternative definitions?
What kind of patterns can you think of for distributed object architectures?
Give an example of a complex software architecture. Can you relate the description of the architecture to the definition given earlier?
Discuss the possible motivations for deploying embedded logic.
How would you extend a given imperative or declarative language with objects?
Discuss the Java Native Interface. Does it provide a solution for the problem posed in the previous question? Explain.
What determines the choice for an architectural style? Give an example!

An excellent book on software architectures is [Practice]. You may also want to visit the SEI architecture site at www.sei.cmu.edu/architecture, which provides definitions, and a wealth of other information. As a discussion of the software engineering implications of CORBA, you may want to read [CorbaPatterns]. If you are interested in multimedia information systems, read [MM]. For more information on ACOI, visit the ACOI website on www.cwi.nl/~acoi .

Æliens

2009

Software architecture

Elements of architecture

Models and views

Definitions

Technological infrastructure

put name(person) on tokenstream

subsections:

midi

native methods

kit_object

in handler.c

smart pointer class

java dispatch

subsections:

Rules of thumb -- selecting an architectural style

Cross-platform development

Research/GNU

Commercial