Information systems design: through adaptivity to ubiquity

Abstract

In a globalised economy the accessibility of services becomes increasingly important for businesses. This has led to a demand that information systems should be ubiquitous in the sense that they are available to all users under all circumstances, everywhere and at all times, and independent of the access devices and channels used. The authors believe the key to meeting that demand is existence of an omnipresent media of interaction and existence of information systems that within that media adapt themselves to context parameters at run-time. The World Wide Web is considered as that omnipresent media. Thus, the task is left to design adaptive information systems in a way that avoids unnecessary replication. In this article it will be shown how context parameters can be utilised to enable system adaptivity. The latter is supposed to increase usability and targets the quality of use, the content, and the functionality. We propose using an algebraic approach that aids in providing the leanest appropriate interface via user typing and story boarding. Our approach furthermore limits the content delivered to a user to the amount that can be dealt with in a usage scenario. The latter is based on defining hyphenation points within the content.

Appendices

Appendix 1: Axioms for Kleene algebras with tests

Story algebras form Kleene algebras with tests. Adding an action fail (or 0)—an action that can never be executed—simply means that the following constraints, i.e. axioms are satisfied:

• + and ; are associative, i.e. for all p, q, r ∈K we must have p+(q+r)=(p+q)+r and p(qr)=(pq)r

• + is commutative and idempotent with 0 as neutral element, i.e. for all p, q ∈K we must have p+q=q+p, p+p=p, and p+0=p

• 1 is a neutral element for ;, i.e. for all p ∈K we must have p1=1p=p

• for all p ∈K we have p0=0p=0

• ; is distributive over +, i.e. for all p, q, r ∈K we must have p(q+r)=pq+pr and (p+q)r=pr+qr

• p^*q is the least solution x of q+px ≤ x and qp^* is the least solution of q+xp ≤ x, using the partial order x ≤ y ≡ x+y=y

In addition, on the Boolean expressions B we use another unary operation $\overline{\,\,\,},$ such that $(B,+,;,\overline{\,\,\,},0,1)$ forms a Boolean algebra. That is, + does not only represent choice, but also logical OR, while ; represents sequential composition and logical AND, and $\overline{\,\,\,}$ represents logical NOT. This overloaded use of symbols does not cause problems.

Appendix 2: An equational reasoning example explained

The story space in Example 2 is a sum of two terms in rectangular brackets. Call the left one and the right one of these LT and RT, respectively. We first consider RT. It has the form (α₀ y+x)*(Σ). Due to the presupposed equation α₀ y+x=x the term RT reduces to xΣ which is exactly the term given in Example 7. It thus is sufficient to furthermore show that LT evaluates to 0 under equational reasoning. That, however, can easily be accomplished, as using the commutativity of the sum, one sees that LT is of the form α₀ y+x with x=(b ₀ a ₀)(b ₀ a ₀)^*(Σ). The presupposed equation thus implies that LT=(b ₀ a ₀)(b ₀ a ₀)^*(Σ). Now, this equals b ₀[a ₀(b ₀ a ₀)^*Σ +0]. As the term in the rectangular brackets is of the form α ₀ y+x with x=0 it follows that LT=b ₀[0]=0 and therefore LT+RT=RT and that implies the result provided in Example 7.