Mind Your Outcomes: The ∆QSD Paradigm for Quality-Centric Systems Development and Its Application to a Blockchain Case Study

This paper directly addresses a long-standing issue that affects the development of many complex distributed software systems: how to establish quickly, cheaply, and reliably whether they can deliver their intended performance before expending significant time, effort, and money on detailed design and implementation. We describe ΔQSD, a novel metrics-based and quality-centric paradigm that uses formalised outcome diagrams to explore the performance consequences of design decisions, as a performance blueprint of the system. The distinctive feature of outcome diagrams is that they capture the essential observational properties of the system, independent of the details of system structure and behaviour. The ΔQSD paradigm derives bounds on performance expressed as probability distributions encompassing all possible executions of the system. The ΔQSD paradigm is both effective and generic: it allows values from various sources to be combined in a rigorous way so that approximate results can be obtained quickly and subsequently refined. ΔQSD has been successfully used by a small team in Predictable Network Solutions for consultancy on large-scale applications in a number of industries, including telecommunications, avionics, and space and defence, resulting in cumulative savings worth billions of US dollars. The paper outlines the ΔQSD paradigm, describes its formal underpinnings, and illustrates its use via a topical real-world example taken from the blockchain/cryptocurrency domain. ΔQSD has supported the development of an industry-leading proof-of-stake blockchain implementation that reliably and consistently delivers blocks of up to 80 kB every 20 s on average across a globally distributed network of collaborating block-producing nodes operating on the public internet.publishedVersio

A formal modeling approach to ontology engineering

Ph.DDOCTOR OF PHILOSOPH

Relating abstract datatypes and Z-schemata

Abstract. In this paper we investigate formally the relationship between the notion of abstract datatypes in an arbitrary institution, found in algebraic specification languages like Clear, ASL, and CASL; and the notion of schemata from the model-oriented specification language Z. To this end the institution S of the logic underlying Z is defined, and a translation of Z-schemata to abstract datatypes over S is given. The notion of a schema is internal to the logic of Z, and thus specification techniques of Z relying on the notion of a schema can only be applied in the context of Z. By translating Z-schemata to abstract datatypes, these specification techniques can be transformed to specification techniques using abstract datatypes. Since the notion of abstract datatypes is institution independent, this results in a separation of these specification techniques from the specification language Z and allows them to be applied in the context of other, e.g. algebraic, specification languages.

Relating Abstract Datatypes and Z-Schemata?

1 Introduction As already noted by Spivey [11], schema-types, as used in the model-oriented specification language Z, are closely related to many-sorted signatures; and schemata are related to the notion of abstract datatypes found in algebraic specification languages. Z is a model-oriented specification language based on set-theory. In the model-oriented approach to the specification of software systems specifications are explicit system models constructed out of either abstract or concrete primitives. This is in contrast to the approach used with algebraic or property-oriented specification languages like CASL [9], which identifies the interface of a software module, consisting of sorts and functions, and states the properties of the interface components using first-order formulas