Attribute correspondences

Because each quality attribute corresponds to a stakeholder performing an action on the system either at design time or at runtime, we can use scenarios of such interactions to explore and evaluate an architecture. The main difference here from our original use of the word scenario (see Section 4.7.4, Scenarios) is that now we are not restricted to only runtime behaviors but include scenarios of system modifications, reuse, and so on. 

Duration This attribute corresponds in table Large Session to the time period from the date the Source has sent its first packet to the date it has sent its last packet. In a similar way, there is a Duration attribute in the Tiny Session table for packets sent to one Host only. 

The complex [Cr(CN)6] is an example of a strong field complex, whereas [Cr(H20)g] is a weak field case. There are N—A electrons to be, attributed corresponding to a sub-configuration of Cr " ". The (lowest... 

Given two schemas, a matcher first evaluates the level of confidence in the correspondence of any pair of attributes. Then, decisions are made as to which attribute correspondences should be retained as part of a schema matching outcome. In recent years, new applications have emerged, putting more and more emphasis on the... 

In this section, we present a simple model of attribute correspondences as a basis for the proposed extensions. The model is based on Marie and Gal [2008], We shall accompany the description with a specific simplified case study that will assist us in demonstrating the three extensions to the basic attribute correspondence model. The case study is about the design of a hotel reservation portal. The portal merges various hotel information databases, adding a mashup applications that assists in positioning hotels on a geographical map. 

To conclude this section, we introduce schema mappings. Let S and T be relational schemas. A relation mapping M is a triple (S, T, m), where S is a relation in S, T is a relation in T, and m is a set of attribute correspondences between S and T. A schema mapping M is a set of one-to-one relation mappings between relations in S and in T, where every relation in either S or T appears at most once. 

Attribute correspondences may hold under certain instance conditions. With contextual attribute correspondences, selection conditions are associated with attribute correspondences. Therefore, a contextual attribute correspondence is a triplet of the form (Ai,Aj,c), where A, and Aj are attributes and c is a condition whose structure is defined in Sect. 3.1. 

Example 2. With contextual attribute correspondences, we could state that R.Card-Info.cardNum is the same as S.HotelCardlnfo.clientNum if R. Card Info, type is assigned with the value RoomsRUs. For all other type values, R.Card-Info.cardNum is the same as S.Cardlnfo.cardNum. These contextual attribute correspondences are given as follows. 

Contextual attribute correspondences are specified in terms of a condition on the value assignments of attributes. A k-context of an attribute correspondence is a condition that involves k database attributes. For k = 0, a contextual attribute correspondence becomes a common attribute correspondence. For k = 1, the condition is simple, of the form a = v, where a is an attribute and v is a constant in a s domain. For example, R.Cardlnfo.type= RoomsRUs . Disjunctive, conjunctive, and general / -contexts generalize simple conditions in the usual way. For example, simple disjunctive k-context for k = 1 is a condition of the form a e (iq, v2, , v. ... 

Contextual attribute correspondences can be modeled with similarity matrices. An entry in the similarity matrix Mjj is extended to be a tuple v,c), where v e [0,1] is a similarity value and c is a context as defined above. This modeling allows a smooth extension of contextual attribute correspondences to matcher ensembles [Domshlak et al. 2007 He and Chang 2005], in which matchers are combined to improve the quality of the outcome of the matching process. For example, Do et al. [2002] and Domshlak et al. [2007] proposed several ways to combine similarity matrices, generated by different matchers, into a single matrix. Such combination, which was based solely on aggregating similarity scores, can be extended... 

The similarity matrix inherently captures attribute correspondence information while r can handle schema level constraints. For example, using only the similarity matrix, one can assume that the contextual attribute correspondence... 

A few challenges arise when designing an algorithm for finding contextual attribute correspondences. First, one may risk overfitting the correspondences to the training data. For example, it is possible that one could find a contextual attribute correspondence stating... 

However, this is not a refinement of an attribute correspondence (R.Hotellnfo. neighborhood, T.Subway.station). 

It has been proposed in Bohannon et al. [2006] that A-contexts with k > 1 will yield more trustworthy contextual attribute correspondences. The algorithm first determines an initial list of 1-context conditions. Then, it creates and evaluates disjunctive conditions that are generated from the original 1-context conditions. The generation of conditions is carried out using view selection. Views are chosen... 

A major performance concern is the determination of candidate attributes for contextual attribute correspondences. The approach above is based on context identification using categorical attributes. Clearly, with more categorical attributes, an exhaustive search of all categorical values becomes more expensive. However, even with a small set of categorical values, the attribute candidates for correspondences depends on the number of attributes in the target database. 

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