Analysis and design of a server-side Web architecture for HMI Embedded Systems

Transcription

1 POLITECNICO DI MILANO Facoltà di Ingegneria dell Informazione POLO REGIONALE DI COMO Corso di Laurea Specialistica in Ingegneria Informatica Analysis and design of a server-side Web architecture for HMI Embedded Systems Relatore: Prof. Fraternali Piero Correlatore: Ing. Brambilla Marco Tesi di laurea di: Arcara Luca matr Anno Accademico 2004/05

2 Italian abstract Traduzione del capitolo Introduction Analysis and design of a server-side Web architecture for HMI Embedded Systems In questi ultimi anni, la diffusione e l importanza dei sistemi embedded ha subito una notevole crescita dovuta alla disponibilità di tecnologie e sistemi adatti a diversi contesti di applicazione. Il significato intrinseco di sistema embedded consiste nel concetto di dispositivo progettato per essere utilizzato in contesti particolari e poco comuni; un sistema embedded risulta quindi essere ideale quando è in grado di adattarsi al più alto numero di situazioni. In questo contesto, i dispositivi HMI (Human Machine Interface) rappresentano validi strumenti per gestire diversi tipi di sistemi complessi quali impianti di produzione, reti o sistemi integrati di gestione degli edifici; questi tipi di soluzione possono essere controllati in maniera semplice ed efficace da un operatore attraverso i dispositivi HMI. Il mercato HMI sta seguendo un andamento che lo sta portando ad un approccio completamente diverso nella gestione e visualizzazione dei dati: un primo passo è consistito nell utilizzare strumenti di visualizzazione più potenti (avendo a disposizione schermi a colori e ad alta risoluzione) e pannelli di controllo interattivi (non solamente con tasti ma anche con touch screen); a causa delle sempre maggiori capacità, e nonostante stringenti requisiti di business e vincoli fisici, i dispositivi HMI stanno andando verso un unificazione con il mondo dei sistemi basati su PC; questo è un esempio di come il concetto di sistema embedded sia basato su un continuo compromesso tra funzionalità e prestazioni; il mercato HMI si sta anche dirigendo verso applicazioni capaci di fornire caratteristiche quali la gestione distribuita di sistemi complessi (accesso remoto), l adattamento automatico in base al diverso canale di accesso (PDA, cellulari, PC) e gestione della mobilità (wireless LAN). Parallelo al contesto HMI vi è la presenza del vasto universo delle applicazioni informatiche; questo mondo si sta evolvendo seguendo il fenomeno della convergenza digitale, il quale è caratterizzato da: dispositivi e applicazioni sempre più potenti e flessibili, e capaci di garantire remotizzazione, multicanalità, mobilità, personalizzazione e adattività; numerose specifiche di standard tecnologici (XML, HTML); successo di interfacce utente e architetture standard (browser, grafica vettoriale, architetture basate su IP, architetture a tre livelli). Inoltre, negli ultimi tempi la capacità di gestire le informazioni in maniera coordinata e integrata costituisce un fattore di sempre più rilevante importanza. E in questo contesto che il progetto Poli-HMI ha origine; un progetto che è nato da un accordo tra una società HMI (identificata in questo documento con il nome HMI-COMPANY a motivo delle informazioni confidenziali in esso contenute) e il Polo Regionale di Como del Politecnico di Milano; una sinergia capace potenzialmente di fondere esperienze in campi completamente diversi del vasto mondo delle applicazioni informatiche. HMI-COMPANY opera nel mercato industriale da molto tempo, mentre il Politecnico è sempre stato all avanguardia rispetto alle più nuove evoluzioni tecnologiche nel mondo dell informatica, e, nello specifico del Polo Regionale di Como, delle applicazioni Web e multi canali. Poli-HMI è un interessante esperimento ed è anche un esempio di collaborazione tra il mondo dell università e dell industria, il cui valore è aumentato dal fatto che nasce da un accordo tra enti aventi due approcci completamente diversi nell affrontare cambiamenti ed innovazione: HMI-COMPANY ha una cultura tradizionale, mentre il Politecnico è più orientato verso l innovazione affrontata con un approccio metodologico ed ingegneristico. I

3 Il fine del progetto Poli-HMI è di portare forti innovazioni nel mondo HMI, con l idea di rinnovare il portafoglio prodotti di HMI-COMPANY; l obiettivo è di essere in grado di garantire nuovi dispositivi che: supportino caratteristiche quali remotizzazione, multicanalità, mobilità, personalizzazione e adattività; lavorino con interfacce utente standard (browser); siano costruiti su architetture basate sul Web; utilizzino standard e framework diffusi nel mondo del Web come XML, HTML, SVG e Flash. Questa attività di rinnovamento industriale aspira a reingegnerizzare il modello architetturale degli attuali prodotti HMI-COMPANY; in particolare, l architettura dovrebbe migrare dall attuale modello monolitico verso un più flessibile modello Web. Il progetto Poli-HMI copre molti aspetti riguardanti le applicazioni informatiche, prendendo in considerazione sia problematiche software che hardware. Per ciò che concerne il sistema software che si intende realizzare, l idea principale è di sviluppare una soluzione Web clientserver (come mostrato nella figura successiva) configurabile tramite un apposito configuratore. Una volta installata, l applicazione consentirà agli operatori di accedere al dispositivo lavorando direttamente sul congegno stesso (compact configuration con client e server che vengono eseguiti sullo stesso dispositivo HMI-COMPANY) oppure attraverso connessione Internet remota (detached configuration con client e server che vengono eseguiti su terminali differenti). Poli-HMI client (terminale remoto) Internet Poli-HMI client (browser) Poli-HMI client (PDA + micro browser) Modello dell interfaccia LAN Ambiente controllato (impianto, edificio, museo) Sistema di modellizzazione dell interfaccia Poli-HMI server Presentation layer (produzione markup e oggetti di interfaccia) Business layer (elaborazione dati XML, personalizzazione, adattamento dinamico interfacce) Data/field interface layer (gestione profile utente, dati di contesto, raccolta dati campo, emissione comandi al campo) HMI standalone Architettura proposta per il nuovo sistema Poli-HMI Questa tesi consiste nell analisi dei requisiti e nel design dell architettura server su cui basare il nuovo sistema Poli-HMI; lo studio è stato effettuato seguendo il modello a cascata per lo sviluppo di software, ossia un processo diviso in fasi, quali analisi, design, implementazione, test, integrazione e manutenzione. In realtà, l approccio è stato leggermente diverso da quello classico definito nel modello a cascata, in quanto ha considerato anche una fase di analisi di tecnologie, studio di un sistema preesistente e sviluppo di prototipi. II

4 Il modo in cui questa tesi è stata sviluppata e i punti principali che sono stati approfonditi possono essere sintetizzati nel seguente elenco: 1. un tema centrale è stata l analisi delle tecnologie che supportano lo sviluppo di applicazioni server. Lo studio si è reso necessario in quanto il progetto Poli-HMI consiste in un approccio completamente nuovo nel mondo dei sistemi embedded, infatti ci sono poche applicazioni embedded esistenti che supportano funzionalità server. Il risultato di questa sezione della tesi si è concretizzato nella proposta di una tecnologia server da utilizzare come base per lo sviluppo successivo del progetto; 2. parte di questo lavoro è stato dato dall analisi dell attuale applicazione HMI- COMPANY; si è reso necessario effettuare questo passo, in quanto si è considerato primario e utile, prima di partire con lo sviluppo del nuovo sistema, conoscere come il sistema HMI-COMPANY è strutturato e quali funzionalità offre; 3. una volta concluse le due analisi sopra descritte è stato possibile partire con la definizione dei requisiti software del nuovo sistema. Allo scopo di ottenere una migliore specifica dei requisiti funzionali, si è preferito effettuare anche l analisi degli Use Case; 4. dopo la definizione dei requisiti è stato preso in considerazione il design della struttura principale su cui basare il nuovo sistema Poli-HMI. Il design è stato sviluppato seguendo un approccio funzionale, caratterizzato dall evidenziazione, per ogni singola funzionalità del sistema, solo dei componenti coinvolti; 5. infine, è stato inoltre sviluppato un prototipo della nuova applicazione Poli-HMI, allo scopo di testare alcune funzionalità della nuova architettura e la sua fattibilità. I capitoli contenuti in questo documento sono: capitolo 2 - Poli-HMI project overview: contiene una spiegazione più approfondita del progetto sviluppato in collaborazione tra HMI-COMPANY e il Politecnico di Milano; capitolo 3 - Server-side Web technologies for embedded systems: analizza tutte le tecnologie che supportano lo sviluppo di applicazioni server-side che possono essere eseguite su sistemi embedded, più nello specifico su sistemi che supportano il sistema operativo Windows CE; capitolo 4 - HMI-COMPANY run-time architecture: contiene uno studio dell architettura run-time che al momento è installata sui prodotti HMI-COMPANY; capitolo 5 - Software Requirement Specifications: specifica i requisiti software del nuovo sistema server-side, supportando inoltre questa analisi con lo studio degli use case; capitolo 6 - Poli-HMI server run-time architecture: definisce il design della parte server del run-time Poli-HMI; capitolo 7 - A prototype of the Poli-HMI architecture: descrive il prototipo sviluppato per effettuare un primo test del nuovo sistema; capitolo 8 - Conclusions and future works: contiene un riassunto del lavoro svolto e presenta alcuni possibili sviluppi futuri. III

5 Ringraziamenti Mi piacerebbe esprimere gratitudine in questo breve spazio a coloro che mi hanno aiutato a raggiungere questo passo importante della mia vita. Un grazie anche per avermi sopportato, soprattutto in questo ultimo periodo in cui sono stato poco disponibile. In particolare vorrei ringraziare coloro che in prima persona hanno supervisionato il mio lavoro quali il Professore Fraternali e l ingegnere Marco Brambilla, che mi hanno assistito nello sviluppo di un approccio ingegneristico alle problematiche di questo progetto. Un ricordo speciale a tutti i ragazzi, compagni di viaggio in questi 5 anni di università. Grazie anche a tutti i colleghi del Politecnico con cui ho collaborato in questi mesi di lavoro: Luca, Davide, Alberto, Antonio, Tommaso, Mattia, Giovanni; in particolare però coloro con cui ho condiviso anche il lavoro e i numerosi pranzi ossia Marco, Paolo e Alessandro. Un ringraziamento anche a Paolo e Davide, i ragazzi dell ufficio ospiti, che hanno contribuito ad allietare questi mesi di tesi, e a Natalino per la disponibilità mostratami nel rispondere alle mie domande. Come non ricordare poi la mia famiglia a cui devo maggiormente il fatto di aver concluso gli studi universitari e che mi ha sopportato in questo periodo in cui sono stato poco presente. Un grazie speciale per la revisione del documento di tesi a mia madre, Michele, Anna, Daniele, Angela, Marco, Paolo, Marco e Alessandro. IV

6 Table of Contents Analysis and design of a server-side Web architecture for HMI Embedded Systems 1 INTRODUCTION POLI-HMI PROJECT OVERVIEW HMI-COMPANY PROJECT OVERVIEW CURRENT VIEW OF INDUSTRIAL APPLICATIONS MARKET AND TECHNOLOGIES TRENDS EVOLUTION THE IDENTIFIED OPPORTUNITIES CURRENT OFFER LIMITATIONS OF HMI-COMPANY AND THE HMI MARKET THE PROPOSED TECHNOLOGICAL INNOVATIONS THE FINAL INNOVATION PROPOSAL PROJECT GOALS HARDWARE AND SOFTWARE ARCHITECTURE RESEARCH PROBLEMS TO BE SOLVED SERVER-SIDE WEB TECHNOLOGIES FOR EMBEDDED SYSTEMS ANALYSIS CONTEXT METHODOLOGY CGI OVERVIEW HOW IT WORKS REQUIREMENTS SUPPORT ADVANTAGES DRAWBACKS SUPPORT ON WINDOWS CE CONCLUSIONS ISAPI INTRODUCTION HOW IT WORKS SUPPORT ON WINDOWS CE INPUT/OUTPUT CAPABILITIES REQUIREMENTS ON WINDOWS CE TESTS AND RESULTS ADVANTAGES DRAWBACKS CONCLUSIONS...19 V

7 3.4 ASP OVERVIEW HOW IT WORKS SUPPORT ON WINDOWS CE REQUIREMENTS ON WINDOWS CE INPUT/OUTPUT CAPABILITIES ADVANTAGES DRAWBACKS CONCLUSIONS ASP.NET OVERVIEW HOW IT WORKS ASP COMPATIBILITY SUPPORT ADVANTAGES DRAWBACKS SUPPORT ON WINDOWS CE CONCLUSIONS WEB SERVICES OVERVIEW HOW IT WORKS CLIENT AND SERVER-SIDE COMPONENTS SUPPORT ON EMBEDDED SYSTEMS INPUT/OUTPUT CAPABILITIES TESTS AND RESULTS WINDOWS CE REQUIREMENTS ADVANTAGES DRAWBACKS CONCLUSIONS CONCLUSIONS ABOUT SERVER-SIDE WEB TECHNOLOGIES HMI-COMPANY RUN-TIME ARCHITECTURE INTRODUCTION OPC EXTERNAL DEVICE MANAGER OPC DA OPC SERVER OPC CLIENT...40 VI

8 4.3 INTERNAL DEVICE MANAGERS INTRODUCTION DATA BUFFER CONFIGURATION MANAGED VARIABLES DATA SERVER INTRODUCTION TAGS EXPORTED METHODS APPLICATION MANAGERS INTRODUCTION PAGE MANAGER GRID VIEWS ALARMS MANAGER RECIPES MANAGER SCRIPTING EVOLUTION OF CURRENT ARCHITECTURE SOFTWARE REQUIREMENT SPECIFICATIONS INTRODUCTION OVERVIEW OF THE NEW ARCHITECTURE REQUIREMENT ANALYSIS AND SPECIFICATIONS NON FUNCTIONAL REQUIREMENTS FUNCTIONAL REQUIREMENTS SUMMARY OF CLIENT-SIDE SOFTWARE REQUIREMENT SPECIFICATIONS USE CASES USER GROUP IDENTIFICATION GENERAL USE CASE DIAGRAM USE CASE SPECIFICATIONS FOR OPERATIVE USERS USE CASE SPECIFICATIONS FOR ADMINISTRATIVE USERS USE CASE SPECIFICATIONS FOR THE GENERAL SYSTEM POLI-HMI SERVER RUN-TIME ARCHITECTURE INTRODUCTION PREMISES NEW SYSTEM GENERAL OVERVIEW PERSONALIZATION DATA MODEL APPLICATION FUNCTIONALITIES INITIALIZATION OF THE APPLICATION...94 VII

9 6.4.2 SESSION LOGIN AUTHENTICATION PAGES CONFIGURATION FILE FIELD DATA RETRIEVAL ALARMS MANAGEMENT VARIABLES VALUE REQUEST COMMANDS EXECUTION LOGGING DESIGN REVISION A PROTOTYPE OF THE POLI-HMI ARCHITECTURE PROTOTYPE SIMULATING THE CONTROL OF A MILK PLANT REQUIRED RESOURCES A PROTOTYPE FOR THE POLI-HMI SERVER ARCHITECTURE REQUIRED RESOURCES RESULTS CONCLUSIONS FUTURE DEVELOPMENTS REFERENCES WEB SITES VIII

10 1 INTRODUCTION Nowadays, diffusion and importance of embedded systems are dramatically increasing due to availability of new technologies and systems that are suitable for many different contexts of application. The intrinsic meaning of embedded system consists in a device designed to be used in particular and uncommon contexts. An ideal embedded system should be able to fit to the highest number of situations. In this context, HMI (Human Machine Interface) devices are valid instruments for managing different types of complex systems like production plants, networks or Computer Integrated Building systems. They allow users to control these kinds of systems in a simple and effective way. HMI market has followed a trend that is bringing it to a completely different approach in the way data are visualized and managed: a first step has consisted in using more powerful view tools (having high resolution with colours) and interaction panel control (with not only keys but also touch screens); because of their growing capabilities, even with tight business requirements or physical constraints, HMI devices are going towards a unification with the world of PC based systems; this is an example of how the concept of embedded systems is based on the continuous compromise between functionalities and performances; it is also directed towards applications able to provide features such as distributed management of complex systems (remote access), automatic adaptation to different channels (PDAs, mobile phones, PCs) and mobility management (wireless LAN). Parallel to the HMI context there is the huge universe of computer applications; this world is evolving according to the digital convergence phenomena, that is characterized by: devices and applications that are more and more powerful and flexible, till being able to guarantee remotization, multi-channel systems, mobility, personalization and adaptivity; the well-established definition of many technological standards (XML, HTML); the success of standard user interfaces and architectures (browsers, vector graphics, IP-based architectures, three-tiers architectures). Furthermore, nowadays the capability to provide an integrated and coordinated management of information is becoming more and more important. It is in this context that the Poli-HMI project takes place; a project that was born from an agreement between an HMI company (referred in this document as HMI-COMPANY due to the contained confidential information) and the Campus of Como of the Politecnico di Milano. It is a synergy that can potentially merge experiences based on completely different aspects of the wide world of computer applications. HMI-COMPANY has been operating in the industrial market for a long time, while the Politecnico has been always up-to-date with the newest technologic evolution of the computer science world, and, specifically at the Campus of Como, with Web and multi-channel applications. This project called Poli-HMI is an interesting experiment and an example of collaboration between university and industrial companies, which value is raised by the fact that it comes from an agreement between two complete different approaches in facing changes and evolution: HMI-COMPANY has a traditional culture, while the Politecnico is more oriented to innovation, always using an engineering-based methodology able to identify and evaluate each technology according to well-established rules. 1

11 The goal of the Poli-HMI project is to apply radical innovations to the HMI world, with the idea to strongly renovate the HMI-COMPANY products portfolio; the plan is to be able to guarantee new devices: supporting features such as remotization, multi-channel systems, mobility, personalization and adaptivity; working with uniform user interfaces (browser); built with a Web-based architecture; using well-established standards and frameworks in the Web world like XML, HTML, SVG and Flash. Hence, this industrial innovation activity aims at the re-engineering of the architectural model of the current HMI-COMPANY products; in particular, the architecture should move from the current monolithic model towards a more flexible Web system. The Poli-HMI project covers many aspects of computer applications, considering both hardware and software solutions. Regarding the software system that is supposed to be implemented, the main idea is to develop a Web client-server application (as it is shown in figure 1.1) that can be configured by means of a design tool. Once deployed, the application will allow the users to access the device through standalone mode (compact configuration with client and server running on the same HMI-COMPANY device) and also through a remote Internet connection (detached configuration with client and server running on different hosts). Poli-HMI client (remote terminal) Internet Poli-HMI client (browser) Poli-HMI client (PDA + micro browser) Interface model LAN Controlled environment (plant, building, museum) Interface modelization system Poli-HMI server Presentation layer (mark-up and interface objects production) Business layer (XML data elaboration, personalization, interfaces dynamic adaptation) Data/field interface layer (user profile management, context and field data collection, commands to the field emission) HMI standalone Figure 1.1: Proposed architecture for the Poli-HMI system This thesis aims to deal with the requirements analysis and the design of the server-side architecture on which basing the new Poli-HMI system; the study has followed a modified waterfall model for software development, that is a process divided into phases, such as requirement analysis, design, implementation, testing, integration and maintenance. The approach has been slightly different from the classical waterfall model, as it has considered also a phase of technology analysis, existing system study and prototypes development. 2

12 The way this thesis has been developed and the main points that have been studied in depth can be summarized in the following list: 1. a central theme has been the analysis of the technologies supporting the development of server-side applications. This study has been necessary because the Poli-HMI project considers a completely new approach in the embedded systems world, in fact there are few existing embedded applications supporting server functionalities. The goal of this part of the thesis has been the proposal of a server technology to be used during the following development of the project; 2. part of this work has consisted in the analysis of the current HMI-COMPANY application; this step has been performed because it has been considered necessary and also useful, before starting with the new system development, to work out how the HMI-COMPANY system is structured and which functionalities it offers; 3. after finishing these two analyses, it has been possible to start defining the software requirements of the new system. In order to obtain a more complete specification of the functional requirements, it has been preferred to perform also a Use Case analysis; 4. after the definition of the requirements, the design of the main structure on which base the new Poli-HMI system has been considered. The design has been developed following a functional approach, that is to highlight, for any functionality of the system, only the components involved in the execution of such functionality; 5. finally, a prototype of the new Poli-HMI application has been developed, in order to test some functionalities of the new architecture and its feasibility. The chapters composing this document are: chapter 2 - Poli-HMI project overview: it contains a deeper explanation of the project developed with the collaboration of HMI-COMPANY and the Politecnico di Milano; chapter 3 - Server-side Web technologies for embedded systems: it analyses all the technologies supporting the development of server-side applications that can run on embedded systems, in particular on systems based on Windows CE O.S.; chapter 4 - HMI-COMPANY run-time architecture: it contains a study of the run-time architecture that at the moment is deployed on the HMI-COMPANY products; chapter 5 - Software Requirement Specifications: it specifies the software requirements for the new server-side system, supporting also this analysis by means of the study of use cases; chapter 6 - Poli-HMI server run-time architecture: it defines the design of the Poli-HMI server-side run-time; chapter 7 - A prototype of the Poli-HMI architecture: it explains the prototype developed for a first test of the new system; chapter 8 - Conclusions and future works: it contains a summary of the work that has been done and some suggested future development lines. 3

13 2 POLI-HMI PROJECT OVERVIEW This work is part of the Poli-HMI project born from the collaboration between HMI-COMPANY and the Politecnico di Milano. The project aims at the analysis, development and prototyping of a new generation of HMI (Human Machine Interface) devices for applications of industrial automation, building automation, home and general system control, with advanced features such as personalization, mobility, multi-channel, adaptive and remote systems. These advanced features shall be studied and inserted inside the company products portfolio; hence, the project considers also a study of the current state of the company from different points of view: products, technologies and production processes. Afterwards the research activity aims at the evaluation of the possible methods and interesting technologies. It is foreseen to reach these project goals through an effort in innovation oriented toward two main directions: 1. the functional and architectural revision of the HMI-COMPANY traditional products portfolio addressed to the industrial automation market; 2. the products flexibility derived from the introduction of the above listed features. 2.1 HMI-COMPANY HMI-COMPANY is a product company that includes in its products portfolio industrial HMI panels; in particular it sells Windows CE touch screen terminals. These products are also supported by two different kinds of applications: configuration software: it is a software provided by HMI-COMPANY that allows the developer to design the model of the plant and to describe the user interface that he/she wants to visualize on the operator panel. Through this single software the user can program all his/her devices. There are different types of configuration software according to the devices they configure; panel-side software: it is a software working at run-time which is able to understand and execute the files generated from the configurator software. Two separated layers cooperate at run-time: data acquisition and presentation. 2.2 Project Overview Current view of industrial applications An HMI (Human Machine Interface) is a device that, placed inside a complex data system (for example a company network, a group of production plants or an advanced system of Computer Integrated Buildings), provides the operator an interface for visualizing and interacting with the information contained within the same system. Hence, HMI regards extremely effective tools for data monitoring and management, that allow the operator to visualize the information, but also to modify the plants state through the introduction of data and values into the same HMI devices. Nowadays, in real terms, these HMI tools allow only a local data monitoring and management; this means that it is possible only when the operator is present near the field that is locally linked to the application or the control server. The interaction is performed using a keyboard or a touch screen that let user to move through the different tags or pages configured in the same HMI device. 4

14 Lately, it is getting more and more urgent the requirement to visualize, control and interact at a data and information level in a remote context: the problem is that, at the moment, it does not exist a remote HMI environment able to obtain acceptable results in the presence of high amount of data and different representations Market and technologies trends evolution The HMI market trend reflects the evolution directions introduced by digital convergence phenomenon in other sectors, such as consumer informatics and management informatics. In these fields, there has been a double evolution: The applications and devices are getting more and more flexible and powerful, using the hardware capacity and network connection that continuously increase their performances. Flexibility and power are embedded in the following features: o remotization: the possibility that the same application can be accessed in a standalone mode, on a local network or on the Internet/Web; o multi-channel system: the possibility that the same application can be viewed on different devices (PC, mobile phone, PDA, smart phone, dedicated devices, etc.); o mobility: the ability to support mobile users, connected to the application according to procedures different from the ones used in systems based on local or fixed geographic networks; o personalization: the ability of an application to serve different contents and commands to different users according to their different characteristics; o adaptivity: the ability of an application to serve different contents and commands to the same user in different moments, according to the interaction context (place, day hour, etc.). There is an increasing presence of these features inside computer applications. The user interfaces and the application architectures have reached a uniform level and some technological standards have imposed themselves on the international scenario; between them there are: o the use of standard browsers as universal interface for accessing applications; o the use of architectures based on the IP protocol (fixed or mobile) as an instrument for local and remote connectivity; o the use of software architectures with three tiers (data, business and presentation) for separating the user interface from the other application functionalities; o the adoption of mark-up languages (HTML, XML, SVG) for data exchange and contents visual rendering; o the adoption of architectures based on Web services for the development of distributed applications based on the HTTP protocol. This evolution has not completely reached the Italian market of HMI products for industrial automation, due to the strong presence on the field of traditional devices and to the conjunctural difficulties of the small/medium companies in elaborating the investment plan necessary to reconvert their own automation infrastructures. Nevertheless, in a medium term the evolution towards HMI devices supporting the features above described will unavoidably happen both on the Italian and the international market and it is already possible to recognize in the biggest international producers (for instance Siemens) some signals of commercial offer orientation towards the above indicated direction. 5

15 2.2.3 The identified opportunities HMI-COMPANY recognizes in the current market situation and the evolution trends above described a double business opportunity: the functional and architectural revision of the HMI-COMPANY traditional products portfolio for the industrial automation market will allow the company to offer a better service to its customers and, as a consequence, to make stronger its current core business, facing the international competition; the products flexibility as a consequence to the introduction of features like remotization, mobility, multi-channel system, personalization and adaptivity will let HMI-COMPANY to access new markets. In particular, the following sectors are considered to be more strategic: o Building Automation and Computer Integrated Building: it regards integrated systems for complex building management, able to provide the operator with an interface for data visualization and for performing commands to control the building; o Home Automation: it regards building automation applications provided for the final user; their goal is to let the user to remotely and locally control the home functioning parameters and to perform video surveillance; o Mobile applications dedicated devices: it regards applications that require special devices for a mobile access to the information, because of the particular use made by the user Current offer limitations of HMI-COMPANY and the HMI market The current products portfolio of HMI-COMPANY and the other principal players in the HMI market is strongly oriented toward traditional applications of industrial automation. The typical architecture of an HMI system is depicted in the following figure. LAN Controlled plant System for interface configuration (offline) Configuration parameters HMI User interface Control logic Interface with the field Figure 2.1: Overall architecture of the current HMI products The above depicted architecture is optimized for the traditional applications of industrial automation that require the installation of the HMI device on the controlled machine or in a network local to the plant; this architecture presents some limitations for what concerns remotization, mobility, multi-channel system, personalization and adaptivity: the access is limited to the standalone use on the controlled machine or the local network; 6

16 the user interface uses a proprietary program and is not based on standard technology (browser and mark-up languages); the software architecture does not aim to make the presentation independent from the business logic. Even if the two software layers are distinct, the lack of a neutral from presentation representation of the information and the commands implies that the logic and the user interface objects are not perfectly isolated from each other; the interface configurability, even if allowed by the configuration system, does not adapt contents and interaction commands to access devices belonging to very different typologies, such as a PC provided with a wide screen and a PDA; mobility absence: the application is designed for being accessed locally or in a fixed network and does not take into consideration mobile access features (band limitations, discontinuity of the link, limited I/O apparatus); personalization absence: the interface configurability is static and does not take into consideration the preferences of the single user; adaptability absence: contents and commands that are present in the interface are not adaptable to the context in which the interaction happens. Furthermore, an evaluation of HMI-COMPANY and HMI market has highlighted also the following aspects: HMI-COMPANY appears to lose the pace with innovation with respect to the new technologies and features. This is particularly clear for Web-based features, such as ing, messaging, remotization of interfaces, browser-based interaction, multidevice rendering; The most aggressive competitors are exploiting internet oriented features for marketing purposes, however they currently provide only low-level features, which can be achieved with small effort. Only a few advanced SCADA products provide real value-added features. Possibly, current customer knowledge is not enough for appreciating the difference The proposed technological innovations The following table shows the innovations proposed in this project to face the above described limitations. Current limitation Proposed innovation The access is limited to standalone use on the controlled machine or the local network. The user interface uses a proprietary program and is not based on standard technology (browser and mark-up languages). Software architecture where presentation and business logic are coupled Limited interface configurability Multifunctional architecture for standalone, local (LAN), fixed remote (Web), mobile remote (Wireless) access. Use of standard browser-based interfaces and mark-up and presentation technologies (HTML, XML, SVG, XML+Flash, ActiveX, Curl, etc.) Adoption of multi-tier architectures with a separate presentation layer. Use of XML as a neutral format for data representation and user interface commands. High level system for representing interface contents. Static and/or dynamic generation of the interfaces for each access channel (PC, PDA, mobile phone, etc.) using XML data. 7

17 Mobility absence Personalization absence Adaptability absence Use of an HMI-server able to produce interfaces suited for mobile access (e.g. GSM/SMS, GPRS or UMTS). Explicit representation in the control logic and in the profile user data; interface customization starting from such profile. Explicit representation in the control logic and in user interaction context data; interface customization starting from such context. Table 2.1: Proposed innovations Thanks to the technological solutions that will be adopted, the new devices will allow to change substantially many access modalities for managing complex system; in fact, it will be feasible to access the system from any remote place with the same interaction and control capabilities given by the local standalone access: in other words, the development of Poli- HMI project will surely lead to the simplification and decrease of costs in controlling and interacting with complex systems, and also to the complete users satisfaction. 2.3 The final innovation proposal The evaluation of HMI-COMPANY current status and HMI market allows defining a product innovation strategy that aims at reaching (and passing over) the current technological status of competitors. The Politecnico di Milano proposal consists in a three-step solution that incrementally increases the features of HMI-COMPANY products in the direction of innovative, Web- based and mobile communications. 1. Web enabling the current product lines As a first step, it is proposed to maintain the current run-time software, operating system and configurator. By introducing a few new components, it can be provided the user with advanced communication features. It is aimed at enabling Web functionalities, based on already available data, that are accessed by the new components. In particular, it is proposed to insert in the system a Web server, a database server (optional), and a (XML configurable) dynamic Web application. The result consists in the possibility of publishing on the Web the plant data and events log. It is also planned a minimal interaction with the field (some non-critical commands can be executed). 2. Remotization of the HMI interface It is proposed to adopt an incremental solution, starting from the previous one: instead of publishing plant status using only traditional Web pages, it is introduced a rendering technology (SVG/Flash) which reproduces the panel interface in a simplified way, using the currently generated configuration files, possibly modified with a few variants. It is also planned some interaction with the field (some commands can be executed). 3. Architecture implementation shifting For the long term solution the proposal consists in a Web-based architecture to be used both for local and remote access. 8

18 2.4 Project goals Hardware and software architecture The following figure shows the overview architecture of the Poli-HMI solution proposed for this project: Poli-HMI client (remote terminal) Internet Poli-HMI client (browser) Poli-HMI client (PDA + micro browser) Interface model LAN Controlled environment (plant, building, museum) Interface modelization system Poli-HMI server Presentation layer (mark-up and interface objects production) Business layer (XML data elaboration, personalization, interfaces dynamic adaptation) Data/field interface layer (user profile management, context and field data collection, commands to the field emission) HMI standalone Figure 2.2: proposed architecture for the Poli-HMI solution Research problems to be solved The evolution towards the Poli-HMI concept and architecture shown in the previous paragraphs involves directly the HMI-COMPANY core business and therefore it must be managed with a proper technical and scientific support. For this reason, the project in discussion considers a strong involvement of the Politecnico di Milano as responsible for the scientific research supporting the development. In particular, the Politecnico researchers have been involved in the following research area: analysis of the competitive scenario of the HMI products; monitoring of the evolution of the technologies that are important for building remote, multi-channel, mobile, personalized and adaptive applications; analysis of the requirements, the architecture specification and the user interfaces; definition of the software engineering and project management procedures suitable to the Poli-HMI systems development; definition of the modalities for analysing the applications performances; application of the concept of Poli-HMI architecture in the arts area. 9

19 3 SERVER-SIDE WEB TECHNOLOGIES FOR EMBEDDED SYSTEMS In order to create an architecture able to support the development of the Poli-HMI solution it has been important to analyse the technologies that can be implemented on embedded systems, considering their features, efficiency and performances. The core of this study has been the server-side of the architecture, therefore in this chapter it is described only an analysis of technologies for creating server applications; furthermore, the focus has been restricted to server-side frameworks providing support for Web solutions. The technologies that have been considered are: CGI (Common Gateway Interface) ISAPI (Internet Server Application Program Interface) ASP (Active Server Pages) ASP.NET Web services 3.1 Analysis context Before starting with the description of server-side technologies it is important to define the context in which the study has been done, in particular it is significant to underline that it has been essentially used only the Windows CE Operating System; the reason for this choice can be found in the fact that, after a detailed evaluation of embedded operating systems, it has come out that only Windows CE and Linux offer the most complete solutions, resulting each one in a low cost and maximum flexibility combination. It has been preferred to analyse Linux and Windows CE in two different studies and in this document only the results concerning Windows CE are given. It must be also emphasized that, at the moment, some of the products of the HMI-COMPANY adopts Windows CE as operating system and this means that HMI-COMPANY has a high competence on this OS. Windows CE is a good compromise between performances, offered functionalities and footprint size. In fact, in an embedded system, it is difficult to find solutions able to reach good performances on a wide range of functionalities without having an exceeding footprint. Microsoft Windows CE 5.0 is an open, scalable, 32-bit operating system (OS) that integrates reliable, real time capabilities with advanced Windows technologies. Windows CE allows you to build a wide range of innovative, small footprint devices. [w1] It must be also mentioned that it is available a tool called Platform Builder for Microsoft Windows CE 5.0 that is a fully-integrated development environment (IDE) for building custom Windows CE OSs and components for embedded system devices Methodology The adopted methodology has been determined by the specific needs of the Poli-HMI project; hence, the following conclusions strictly apply to this specific context. The following sections analyse and evaluate the above listed technologies; the paragraph structure for each technology consists in: overview: it gives a general description of the technology; how it works: it explains the components and the processes involved in the execution of applications built using the technology; 10

20 support: it gives a list of operating systems and/or Web servers supporting the technology; support on Windows CE: it considers the possibility to run on Windows CE applications built with the technology; requirements: it gives a list of the software requirements for running the technology; requirements on Windows CE: it considers the requirements applying to a possible Windows CE implementation; Input/Output capabilities: it evaluates the capacity of the technology to support Input/Output operations such as file, XML file and databases management; advantages: it lists the advantages in adopting the technology; drawbacks: it lists the disadvantages in adopting the technology; conclusions: it gives a final evaluation of the technology. In the following paragraphs it is possible to find technologies evaluation according to their Input/Output capabilities. The libraries identified and tested have been only the ones considered to be a standard way for performing I/O functions. To determine if a library could be seen as a standard way or not, two aspects have been evaluated: the company that produces and supports the library: it makes sense to study and test software that is developed by a software company that is well-know in the computer applications world and that also offers other software products; an example is Microsoft s products that have been used for this analysis; search on the Web of code samples for performing I/O functionalities: it can be considered to be an important parameter of evaluation, in fact the Internet community of programmers offers a wide range of code samples; usually these examples use the most standardized code. It must be said that the sources which the samples are downloaded from must be always checked, in fact it may be that sometimes they are not reliable. More in general, one of the main aspects that has been considered is the need of robustness and commercial feasibility of the solutions: for example it does not make sense to try some libraries that are not standard or that are not supported by a proper development team; indeed, these technologies would be too risky for HMI-COMPANY, since all the future versions of HMI-COMPANY products would depend on not well supported software. 3.2 CGI Overview CGI stands for Common Gateway Interface, a standard for interfacing external applications with information servers, such as HTTP or Web servers. It simply may be intended as an agreement between HTTP server and such external applications about how to communicate. External applications may be scripts or programs: the difference is that scripts are lists of commands written in a scripting language (like PERL, TCL) which are compiled and executed at run-time, while programs are standalone compiled executable files written in traditional programming languages (like C, C++, VB, etc.): a CGI script or a program is a program that the Web server can invoke. Invocation can be provided with in input explicit (from a Web form) or implicit (from HTTP header) data. 11

21 Originally, CGI was invented by NCSA (National Center of Supercomputing Applications) for the NCSA HTTPd Web server in 1993, so it is a relatively old technology which has been gradually replaced by more powerful techniques. On the other hand, it is still used especially in old-generation applications which use separate CGI programs to generate dynamic Web content. The programming language PERL is well known as a language used for CGI, but one of the points of CGI is to be language-neutral: the Web server does not need to know anything about the language used for development, therefore it is possible to use every type of language and any operating system; it must be considered that scripting languages require a script interpreter plug-in installed in the Web server but they are easier to debug, modify, and maintain than a typical compiled program How it works The way CGI works from the Web server point of view is that certain locations are defined to be served by a CGI program. Whenever a request to a matching URL is received, the corresponding program is called, with any data that the client has sent as input. Output from the program is collected by the Web server, augmented with appropriate headers, and sent back to the client. The following figures illustrate this process more in detail: Figure 3.1: The GET request is sent by the client Figure 3.2: The Web server starts the CGI script/program 12

22 Figure 3.3: The output of the script is sent to the Web server Figure 3.4: The HTTP response is sent to the client The Web server and the CGI programs communicate in four major ways: environment variables, command line, standard input and standard output. The first three ways are used to pass data from the client HTTP request (POST or GET) to the CGI program, while the last is used to return data to the client. Environment variables allow to maintain and to pass information state between independent HTTP request (HTTP is a stateless protocol): they are set when the server executes the external program Requirements As it is a long-time asserted standard, CGI is supported by any modern Web server; owning a CGI-enabled Web server is the only requirement needed to execute CGI scripts. CGI scripts and programs may be directly requested from a simple HTML page, so it is not necessary to provide the Web server with scripting capabilities (like ASP, PHP, JSP, etc.) Support Despite it is a relatively old technology, developing CGI extensions is quite easy and there is a wide active developers community which supports it providing solutions to common and specific problems. Developing in CGI can be considered a home-made solution without additional costs beside simple time spent in building source code. 13

23 3.2.5 Advantages Summarizing, it can be identified a list of advantages in implementing a CGI application: language-neutral: as it has been previously written CGI does not depend on the language used to build the program; architecture-independent: the CGI program is independent from the architecture it is installed on; open standard; no license/run-time cost: it is not a proprietary standard; process isolation: the program is independent from other processes, hence it depends only on its execution environment Drawbacks As any old technology, there are some disadvantages in using CGI: main problems affect security and performances. Since a CGI program is executable, it is basically the equivalent of letting the world run a program on a system, which is not particularly safe. Therefore, there are some security precautions that need to be implemented when using CGI programs. Typically these safety measures regard access permission to the directory where CGI scripts are located, so extra time to configure Web server is needed in order to protect it against not permitted executions. Although this, security cannot be fully guaranteed. CGI was originally conceived to define a standard for communication between Web server and external applications, therefore lifecycle of CGI programs is quite resource-consuming: when the Web server receives a request which refers to a CGI program, it must create a new process in order to execute the program and, for passing to this application all the information that could be necessary in order to generate the response, it can only communicate by means of environment variables and standard input. The creation of a process for each request is time-consuming and remarkably engages the resources of the Web server, factor which limits the number of requests that the Web server can manage. A direct consequence is that programs cannot interact with the Web server or take advantage of its abilities as they take place in separate processes. As an example, a CGI script cannot write on the Web server log. There is also an alternative technology, called FastCGI, which is more performing as it uses a single persistent process to execute the CGI program, but it does not contribute in any way to make more interactive the Web server and the external program Support on Windows CE The Windows CE Web Server is implemented as an installable device driver, which is loaded at the start-up of the system; on this Web server there is no support for CGI applications and it is also reasonable to believe that it will not be supported even in the future Conclusions CE Web server limitations do not allow the use of CGI technology. Anyway, other serious limitations of this technology (especially performances) would not have made its choice preferable as time requirements are very strict in the Poli-HMI project; indeed, frequent consecutive requests to Web server which make use of CGI programs, would be extremely resource-consuming as there is much overhead generated by processes that are activated each time a request is issued. 14