Asp ects of Building W eb Application Systems Using the - PDF document

Asp ects of Building W eb Application Systems Using the MBASE Approac h Anca-Juliana Stoica 15th In t F orum on SCM/F o cused W orkshop, USC-CSE, Oct.2000

Con ten ts 1. In tro duction 2. W eb Application Systems 3. Arc hitecture 4. W eb T ec hnologies 5. Asp ects of Building W AS (a) The Pro cess (b) Requiremen ts and Use Cases 6. Additional Mo deling Issues Connected to W AS (a) W eb Application Extension of UML 7. Applying the MBASE Approac h to W AS Dev elopmen t 8. Cost Mo deling and Estimation (a) Mo deling and Estimation (b) An Algorithm for Estimation based on Use Cases 9. Conclusion

I. In tro duction W eb Application Systems W AS is a W eb System (WS) that allo ws its users to execute business logic with a bro wser. A W AS: is dynamic � facilitates collab orativ e con ten ts, and distributed � comm unities on the w eb deals with man y di�eren t stak eholders � has to b e arc hitected for con tin uous c hange � has to cop e with p erio ds of p eak in teraction � uses sp eci�c W eb tec hnologies suc h as: HTML, XML, � EJB, SSL, CGI, TCIP/IP , ASP , JSP , ...

Mo del Based (System) Arc hitecting and Soft w are Engineering The MBASE approac h: is the most complete system of in terconnected mo dels � for soft w are dev elopmen t to date has a sound theoretical foundation � o�ers supp ort for analysing mo del clashes � has �exibilit y , adaptabilit y , ease of extension. �

W e found that the MBASE approac h is v ery useful for represen tation of the success, pro duct, pro cess, and prop ert y asp ects of a W AS and that there is a synergy b et w een dev eloping W AS and dev eloping MBASE, in the sense that: MBASE o�ers the framew ork for analysing and � mo delling W AS to meet the critical success factors for soft w are pro jects W AS o�ers the information to enhance MBASE mo dels � (or create new ones) for this sp eci�c soft w are systems.

I I. W eb Application Systems W eb Application Systems are built b y w ebifying clien t/serv er systems and in tegrating legacy . T ypically these systems are asso ciated with: an infrastructure - the W eb system � a business logic - the W eb application � an arc hitecture for the W eb application � enabling tec hnologies, dynamic clien ts, and distributed � ob jects. The most adv anced suc h systems reengineer and automate complete businesses pro viding highly p ersonalized, adaptiv e solutions. Some c haracteristics asso ciated with dev eloping W AS are: externally imp osed and complex rules and regulations � customer fo cus � in terface with legacy data structures � increased concern for p erformance and reliabilit y . �

I I I. Arc hitecture The most basic arc hitectural comp onen ts are: clien t bro wser � net w ork connection � W eb serv er � application serv er, whic h enables the system to manage � business logic and state.

Figure 1: Generalized W AS arc hitecture.

The basic arc hitectural comp onen ts are used in 3 arc hitectural patterns, or fundamen tal structural organization sc hemas: Thin W eb Clien t � Thic k W eb Clien t � W eb Deliv ery System � The di�erence from traditional clien t/serv er systems is that W AS construct W eb-sp eci�c comp onen ts, namely W eb pages. These are arc hitecturally signi�can t comp onen ts b ecause they exist b oth in the mo del and in the executable system.

IV. W eb T ec hnologies Enabling T ec hnologies Pro vide the infrastructure for building W eb applications, in particular the mec hanism b y whic h W eb pages b ecome dynamic and resp ond to user input. Examples include: CGI (Common Gatew a y In terface), Activ e Serv er P ages (ASP), Ja v a Serv er P ages (JSP), servlets, and W eb serv er APIs suc h as ISAPI (In ternet Serv er API), NSAPI (Netscap e Serv er API) Enabling tec hnologies are used as dev elopmen t en vironmen ts that lead to new business opp ortunities. New business opp ortunities, in turn, lead to c hanged business practices (see Fig.2).

Enabling New Business Changed Business Technologies. Opportunities. Practices. Figure 2: The role of enabling tec hnologies.

Other W eb tec hnologies are used for: creating co de from UML mo dels: ASP , VBScript � clien t-side scripting: HTML, XML, Ja v aScript, � VBScript, Applets, Activ e X con trols, DOM clien t-serv er proto cols: HTTP , DCOM, CORBA/I IOP , � Ja v a RMI securing the W AS: sc hemes to protect con�den tial � information o v er the net suc h as SET (Secure Electronic T ransaction), SSL(Secure So c k et La y er)

V. Asp ects of Building W AS A. The Pro cess more customer orien tation (\customer" here is de�ned � as a user of a compan y) the role of use cases that: i) driv e the pro cess, ii) are a � resource for nearly ev ery activit y in the pro cess, iii) help manage and attac k risks, and iv) ev ery w ork er t ypically reviews the use cases to v alidate decisions made during w ork activities the relationships with the business pro cess � more stak eholders to consider for the Win-Win � nego ciations the in�uence of: enabling tec hnologies, sp eci�c � arc hitectures, and new comp onen ts (suc h as the W eb pages) the \dev eloping W eb-time" approac h � the new approac h to W eb UI protot yping � new artifacts �

B. Requiremen ts and Use Cases collection of do cumen ts and mo dels to unam bigously � describ e the soft w are to b e built use cases capture and express the system b eha vior � business mo dels giv e input to the use case view and � help to iden tify actors and use cases dev eloping W eb-time solutions imply to unify creativ e � design and soft w are engineering pro cesses.

VI. Additional Mo deling Issues Connected to W AS A. W eb Application Extension of UML

Icon Server Page Client Page Form Frameset Target

Examples of using the W eb Application Extension of UML

VI I. Applying the MBASE Approac h to W AS Dev elopmen t A.Mo del Systems MODEL SYSTEM Delivered software Users system requirements Figure 3: Mo del system.

B.The MBASE approac h applied to W AS.

Success Models * Win−Win * User−Centered * Creative Design * Mission−Critical * Business Model * Decision Framework Process Models Product Models Entry / Exit V & V Criteria Criteria * Win−Win Spiral * Architectural Patterns for WAs * RUP 2000e * WAS artifacts. * Major Milestones (web pages, forms, Product Development & Evolution Process framesets, targets..) * LCO * UML and WAE * LCA * Enabling Technologies * IOC * COTS and RAD Evaluation and Analysis Property Models. * Cost and Schedule * Use Case Metrics * Robustness, Scalability, Feature Richness, Response Time, Usability * Sizing Metrics * Progress and Quality Metrics

VI I I. Cost Mo deling and Estimation A. Mo deling and Estimation Goal Definition. Choose a Model. (Data Dependence) Choose Model Structure. Parameter Estimation Collected Data. New Data. No. Validation. Yes. Use The Model.

An Algorithm for Estimating W ork With Use Cases 1. T otal actors 3 P T ( na ( W a = ) ) � a i i i =1 i = S = A =C : Complexit y: Simple/Av erage/Complex : na =n um b er of a v erage actors; W a =W eigh t of an actor. Actors complexit y in terms of actor in teraction mec hanisms: API / Comm unication Proto cols / GUI. 2. T otal Use Cases 3 P T = ( nuc ) ( W uc ) � uc j j =1 j j = S = A =C : nu =n um b er of use cases; W uc =w eigh t of a use case. Use case's complexit y in terms of transactions p er U.C. or n um b er of analysis classes / U.C.

3. Unadjusted use case p oin ts U U C P = T + T a uc 4. T ec hnical Complexit y of the Pro ject 13 P T C F = 0 : 6 + 0 : 01 ( V tf ) ( W tf ) � � k k =1 k 13 =factors con tributing to complexit y (ho w di�cult the system will b e to construct). TCF is similar to F unction P oin ts. 5. Exp erience lev el of the p eople on the pro ject (The En vironmen tal F actor). 8 P E F = 1 : 4 0 : 03 ( V ef ) ( W ef ) � � � l l =1 l 8 =factors con tributing to e�ciency .