The notion of Timeline has been used informally in spacecraft operations software for some time, but it has not heretofore been formalized and unified either syntactically or semantically. In this work, the Timeline has been formalized and unified so that the commonality can be exploited to reduce the cost of developing and using spacecraft operations software. The Timeline can then be used as the common data structure for storage and communications between spacecraft planning and operations software elements.
Most spacecraft planning and operations processes are naturally expressed in terms of software tools that read timelines from databases as input and generate results as new or modified timelines that are written to the databases. Timelines are rigorously versioned, and each version is immutable — thus, a versioned timeline name forever represents exactly the same contents. The name is therefore as good as the contents, and the need for keeping files of contents for communicating between programs, or for associating several timelines or even values on those timelines, or for keeping a record of past values, is eliminated. Timelines thus form the syntactic and semantic method of integration of software elements, leading to decreased adaptation cost.
Operations efficiency is increased because historically segregated elements are easily integrated so that there are fewer gaps in the operations process that must currently be closed, if they are closed at all, by expensive or inefficient means.
The Timeline is abstractly defined as a container of items indexed by time, or of items related by time. The abstract definition is intentionally rather open, and the edge between timeline and not-timeline is fuzzy. The abstract definition does not need to be formalized, because it is the type of timeline that is actually defined that has practical impact. Timelines are made practical by creating concrete types of timelines that can be precisely defined, stored in databases, manipulated in software, and so on.
Timeline instances are stored in timeline databases (TLDBs). All TLDB instances must have two properties beyond the obvious of providing for the storage and retrieval of timelines: they must be rigorously versioned, meaning that in principle every change to a timeline creates a new version of that timeline; and they must provide version immutability, meaning that once a version is created, it is never changed. The reason for this is so that a timeline name and version together precisely represent the contents of that timeline at some instant in time.
The Database Interface is a key architectural invariant, along with the Timeline. It is designed to allow the database technology to be selected to meet mission needs. For example, a small mission may choose to use a free database. A larger mission may choose to use a commercial database that provides robust hot backups, offsite mirroring, local caching, and the like. A mission may choose to put the data in a commercial cloud. It may even change DB technologies over the life of the mission, using something cheap and light in formulation, heavy in operations, and optimized for archival access in perpetuity. The interface stays the same no matter what technology is used by a project, so that the spacecraft operations software suite will operate the same regardless of the DB technology used.
Interfaces can be added and extended, so that when a new timeline major type is introduced, the interfaces can be systematically extended to support the new timeline type.
This work was done by William K. Reinholtz of Caltech for NASA’s Jet Propulsion Laboratory.
The software used in this innovation is available for commercial licensing. Please contact Dan Broderick at
This Brief includes a Technical Support Package (TSP).
Timeline Central Concepts
(reference NPO48353) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) that outlines the "Timeline Central Concepts" as part of the NPO-48353 initiative. It emphasizes the importance of managing and preserving data through a structured timeline approach, which is crucial for the operations of interplanetary missions.
Key highlights include:
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Fundamental Changes in Data Management: The document discusses significant changes in how data is named, preserved, and managed. By naming and preserving each version of data, the need for stashing and passing files is eliminated, reducing the complexity of data management systems. This approach also introduces a Naming Service that maps data names to their current locations, facilitating efficient data migration and management across various repository types.
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Computation Model: The document presents a scalable and auditable computation model that allows for repeatable computations on timelines. This model is designed to be highly regularized, enabling users to manipulate computations easily, whether by storing results or re-deriving them as needed. The system is also scalable to cloud environments, enhancing its flexibility and accessibility.
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Timeline Types: Various types of timelines are defined, including State, Measurement, Event, and Activity timelines. The document emphasizes the importance of the SCN (System Change Notification), which ensures that every mutation of every timeline is named and retained immutably, thus preserving historical data for future reference.
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Implementation Status: The document outlines the current status of the implementation of the information model, which includes the establishment of measurement, state, event, and activity timelines, as well as the use of triplestore and filestore for metadata and unstructured data. This structured approach significantly eases the migration to new architectures and reduces software costs.
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Benefits of Formalizing Timelines: By formalizing timelines and integrating them into databases, the document highlights the reduction of ad-hoc interfaces and custom storage systems, leading to a more efficient execution model characterized by read-compute-write operations.
Overall, the document serves as a comprehensive overview of the advancements in timeline management within NASA's interplanetary operations, showcasing how these innovations can lead to improved data handling, reduced costs, and enhanced operational efficiency.
