Naming issues in the design of transparently distributed operating systems

PhD ThesisNaming is of fundamental importance in the design of transparently distributed operating systems. A transparently distributed operating system should be functionally equivalent to the systems of which it is composed. In particular, the names of remote objects should be indistinguishable from the names oflocal objects. In this thesis we explore the implication that this recursive notion of transparency has for the naming mechanisms provided by an operating system. In particular, we show that a recursive naming system is more readily extensible than a flat naming system by demonstrating that it is in precisely those areas in which a system is not recursive that transparency is hardest to achieve. However, this is not so much a problem of distribution so much as a problem of scale. A system which does not scale well internally will not extend well to a distributed system. Building a distributed system out of existing systems involves joining the name spaces of the individual systems together. When combining name spaces it is important to preserve the identity of individual objects. Although unique identifiers may be used to distinguish objects within a single name space, we argue that it is difficult if not impossible in practice to guarantee the uniqueness of such identifiers between name spaces. Instead, we explore the possibility of Using hierarchical identifiers, unique only within a localised context. However, We show that such identifiers cannot be used in an arbitrary naming graph without compromising the notion of identity and hence violating the semantics of the underlying system. The only alternative is to sacrifice a deterministic notion of identity by using random identifiers to approximate global uniqueness with a know probability of failure (which can be made arbitrarily small if the overall size of the system is known in advance).UK Science and Engineering Research Council

IVOA Recommendation: IVOA Identifiers Version 1.12

An IVOA Identifier is a globally unique name for a resource. This name can be used to retrieve a unique description of the resource from an IVOA-compliant registry. This document describes the syntax for IVOA identifiers as well as how they are created. An IVOA identifier has two separable components that can appear in two equivalent formats: an XML-tagged form and a URI-compliant form. The syntax has been defined to encourage global-uniqueness naturally and to maximize the freedom of resource providers to control the character content of an identifier

Uniqueness typing for a higher-order language

We investigate type-based analysis for a higher-order channel passing language with strong update, whereby messages of a different kind are communicated over the same channel. In order to reason about such programs, our type system employs the concept of uniqueness to be able to assert when it is safe to change the object type a channel. We design a type system based on this concept and prove that our type system is sound, meaning that it only accepts programs that do not produce runtime errors.peer-reviewe

Community next steps for making globally unique identifiers work for biocollections data

Biodiversity data is being digitized and made available online at a rapidly increasing rate but current practices typically do not preserve linkages between these data, which impedes interoperation, provenance tracking, and assembly of larger datasets. For data associated with biocollections, the biodiversity community has long recognized that an essential part of establishing and preserving linkages is to apply globally unique identifiers at the point when data are generated in the field and to persist these identifiers downstream, but this is seldom implemented in practice. There has neither been coalescence towards one single identifier solution (as in some other domains), nor even a set of recommended best practices and standards to support multiple identifier schemes sharing consistent responses. In order to further progress towards a broader community consensus, a group of biocollections and informatics experts assembled in Stockholm in October 2014 to discuss community next steps to overcome current roadblocks. The workshop participants divided into four groups focusing on: identifier practice in current field biocollections; identifier application for legacy biocollections; identifiers as applied to biodiversity data records as they are published and made available in semantically marked-up publications; and cross-cutting identifier solutions that bridge across these domains. The main outcome was consensus on key issues, including recognition of differences between legacy and new biocollections processes, the need for identifier metadata profiles that can report information on identifier persistence missions, and the unambiguous indication of the type of object associated with the identifier. Current identifier characteristics are also summarized, and an overview of available schemes and practices is provided