Ignorance in the Relational Model

We hypothesize that an extension-with-conditioning of Dempster-Shafer theory is suitable for encoding uncertainty and ignorance in the Relational Model. We present a formal and well-motivated definition of conditioning, and show the spirit of the required change in the Relational Model and some results that then follow. It remains to be investigated whether these results are satisfactory

Characterization of order-like dependencies with formal concept analysis

Functional Dependencies (FDs) play a key role in many fields of the relational database model, one of the most widely used database systems. FDs have also been applied in data analysis, data quality, knowl- edge discovery and the like, but in a very limited scope, because of their fixed semantics. To overcome this limitation, many generalizations have been defined to relax the crisp definition of FDs. FDs and a few of their generalizations have been characterized with Formal Concept Analysis which reveals itself to be an interesting unified framework for charac- terizing dependencies, that is, understanding and computing them in a formal way. In this paper, we extend this work by taking into account order-like dependencies. Such dependencies, well defined in the database field, consider an ordering on the domain of each attribute, and not sim- ply an equality relation as with standard FDs.Peer ReviewedPostprint (published version

A formal specification in Z of the relational data model, version 2, of E.F. Codd

Presents a formal definition of the basic concepts of the relational data model, including some additional features introduced by RM/V2. The formal notation used here is Z, a model-oriented specification language

Relational transducers for declarative networking

Motivated by a recent conjecture concerning the expressiveness of declarative networking, we propose a formal computation model for "eventually consistent" distributed querying, based on relational transducers. A tight link has been conjectured between coordination-freeness of computations, and monotonicity of the queries expressed by such computations. Indeed, we propose a formal definition of coordination-freeness and confirm that the class of monotone queries is captured by coordination-free transducer networks. Coordination-freeness is a semantic property, but the syntactic class that we define of "oblivious" transducers also captures the same class of monotone queries. Transducer networks that are not coordination-free are much more powerful

Relational Approach to Knowledge Engineering for POMDP-based Assistance Systems as a Translation of a Psychological Model

Assistive systems for persons with cognitive disabilities (e.g. dementia) are difficult to build due to the wide range of different approaches people can take to accomplishing the same task, and the significant uncertainties that arise from both the unpredictability of client's behaviours and from noise in sensor readings. Partially observable Markov decision process (POMDP) models have been used successfully as the reasoning engine behind such assistive systems for small multi-step tasks such as hand washing. POMDP models are a powerful, yet flexible framework for modelling assistance that can deal with uncertainty and utility. Unfortunately, POMDPs usually require a very labour intensive, manual procedure for their definition and construction. Our previous work has described a knowledge driven method for automatically generating POMDP activity recognition and context sensitive prompting systems for complex tasks. We call the resulting POMDP a SNAP (SyNdetic Assistance Process). The spreadsheet-like result of the analysis does not correspond to the POMDP model directly and the translation to a formal POMDP representation is required. To date, this translation had to be performed manually by a trained POMDP expert. In this paper, we formalise and automate this translation process using a probabilistic relational model (PRM) encoded in a relational database. We demonstrate the method by eliciting three assistance tasks from non-experts. We validate the resulting POMDP models using case-based simulations to show that they are reasonable for the domains. We also show a complete case study of a designer specifying one database, including an evaluation in a real-life experiment with a human actor

A definition of redundancy in relational databases

The relational data model as proposed by Codd is a well-established method for data abstraction. Two essential aspects in this model are the definition of the data structure via the relation scheme and the data semantics via data dependencies. Various classes of data dependencies have been studied in the past. In the presence of data dependencies "update dependencies" (or anomalies) and "redundancy" may occur as first observed by Codd. Normal forms have been proposed as a means to control update anomalies and redundancy. But as the notion of redundancy has never been formally defined, one cannot make any precise statement concerning the presence or absence of redundancy for a given design. In this paper we attempt to provide a formal definition of the notion of redundancy for the case of a single relation respectively relation scheme. We first give a static semantic definition of redundancy and then present an operational analogue. Intuitively speaking a relation r contains redundancy, if some "part" of the information given in r can be "determined" from the "rest" of r. And a relation scheme with a given set of data dependencies admits redundancy if there is a relation belonging to this scheme that contains redundancy. The paper is organized in six sections. Section 1 contains the definition of the relational model that we use. We make use of partial "relations" that are built from constants and variables. In section 2 we present the semantic definition of redundancy. Section 3 introduces a class of data dependencies, i.e. implicational dependencies and a chase procedure for partial relations. Section 4 gives an operational characterization of redundancy. The main theorem in this section is theorem 4.3. It states that a relation r in a class of relations sat(D) contains redundancy if there exists a partial relation q that "contains less information" than rand for which chase D(q

Shareholder Value and Auditor Independence

This Article questions the practice of framing problems concerning auditors\u27 professional responsibility inside a principal-agent paradigm. If professional independence is to be achieved, auditors cannot be enmeshed in agency relationships with the shareholders of their audit clients. As agents, the auditors by definition become subject to the principal\u27s control and cannot act independently. For the same reason, auditors\u27 duties should be neither articulated in the framework of corporate law fiduciary duty, nor conceived relationally at all. These assertions follow from an inquiry into the operative notion of the shareholder-beneficiary. The Article unpacks the notion of the shareholder and tells a particularized story about the shareholder interest. The exercise complicates the agency description, highlighting multiple and unstable shareholder demands that displace the unitary model of the shareholder usually brought to bear. This fragmented and volatile model of the shareholder provides neither a basis for articulating a coherent set of instructions respecting aggressive accounting nor for imposing conservative accounting. The Article concludes that legal positivism provides a more appropriate conceptual framework. Auditor duties should be conceived in formal rather than relational terms, with fidelity going to the rules and the system that auditors apply rather than to a client interest

characterization of order-like dependencies with formal concept analysis

Functional Dependencies (FDs) play a key role in many fields of the relational database model, one of the most widely used database systems. FDs have also been applied in data analysis, data quality, knowledge discovery and the like, but in a very limited scope, because of their fixed semantics. To overcome this limitation, many generalizations have been defined to relax the crisp definition of FDs. FDs and a few of their generalizations have been characterized with Formal Concept Analysis which reveals itself to be an interesting unified framework for characterizing dependencies, that is, understanding and computing them in a formal way. In this paper, we extend this work by taking into account order-like dependencies. Such dependencies, well defined in the database field, consider an ordering on the domain of each attribute, and not simply an equality relation as with standard FDsPostprint (published version