IT: Service Level Agreement (Definitions)

"A signed agreement of system service requirements between two parties (such as your company and an ASP or between your department and end users) that defines the guidelines, response times, actions, and so on, that will be adhered to for the life of the agreement." (Allan Hirt et al, "Microsoft SQL Server 2000 High Availability", 2004)

"A contract with a service provider, be it an internal IT organization, application service provider, or outsourcer, that specifies discrete reliability and availability requirements for an outsourced system. An SLA might also include other requirements such as support of certain technology standards or data volumes. An outsourcer’s failure to adhere to the terms laid out in an SLA could result in financial penalties." (Evan Levy & Jill Dyché, "Customer Data Integration", 2006)

"A formal negotiated agreement between two parties. It is a contract that exists between customers and their service provider, or between service providers. It records the common understanding about services, priorities, responsibilities, guarantees, and so on, with the main purpose to agree on the level of service." (Tilak Mitra et al, "SOA Governance", 2008)

"An agreement between a customer and a product or service provider that defines conditions under which the provider will offer support or additional services to the customer, and what level of services will be offered under each of those conditions." (Steven Haines, "The Product Manager's Desk Reference", 2008)

"An agreement between a service provider and a service recipient that formally defines the levels of service that are to be provided." (David G Hill, "Data Protection: Governance, Risk Management, and Compliance", 2009)

"A formal negotiated agreement between two parties that usually records the common understanding about priorities, responsibilities, and warranties, with the main purpose of agreeing on the quality of the service. For example, an SLA may specify the levels of availability, serviceability, performance, operation, or other attributes of the service (such as billing and even penalties in the case of violations of the SLA)." (David Lyle & John G Schmidt, "Lean Integration", 2010)

"A written legal contract between a service provider and client wherein the service provider guarantees a minimum level of service." (Linda Volonino & Efraim Turban, "Information Technology for Management" 8th Ed., 2011)

"A contracted guarantee of service delivery for a program, transaction, service, or workload." (Craig S Mullins, "Database Administration", 2012)

"The part of a contract between two parties that outlines the delivery of services within defined timeframes." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"A statement to customers or the user community about the service the IT department will provide. It can refer to a variety of metrics, such as performance, up-time, resolution time, and so on." (Bill Holtsnider & Brian D Jaffe, "IT Manager's Handbook" 3rd Ed., 2012)

"An agreement between an IT service provider and a customer to provide a specific level of reliability for a service. It stipulates performance expectations such as minimum uptime and maximum downtime levels. Many SLAs include monetary penalties if the IT service provider does not provide the service as promised." (Darril Gibson, "Effective Help Desk Specialist Skills", 2014)

"The service or maintenance contract that states the explicit levels of support, response time windows or ranges, escalation procedures in the event of a persistent problem, and possible penalties for nonconformance in the event the vendor does not meet its contractual obligations." (Robert F Smallwood, "Information Governance: Concepts, Strategies, and Best Practices", 2014)

"A contract for formally defined services. Particular aspects of the service (scope, quality, responsibilities) are agreed between the service provider and the service user. A common feature of an SLA is a contracted delivery time of the service or performance." (Thomas C Wilson, "Value and Capital Management", 2015)

"A portion of a service contract that promises specific levels of service." (Weiss, "Auditing IT Infrastructures for Compliance" 2nd Ed, 2015)

"A contract between a service provider (either internal or external) and the end user that defines the level of service expected from the service provider." (Project Management Institute, "A Guide to the Project Management Body of Knowledge (PMBOK® Guide)", 2017)

Data Management: Data Contracts (Definitions)

"Data contracts specifically define the data that is being exchanged between a client and service. The data contract is an agreement, meaning that the client and the service must agree on the data contract in order for the exchange of data to take place. Note that they don't have to agree on the data types, just the contract." (Pablo Cibraro & Scott Klein, "Professional WCF Programming: .NET Development with the Windows Communication Foundation", 2007)

"A data contract is an agreement between a client and a service that conceptually depicts the data to be exchanged. Data contracts define the data types that are used in the service." (Nagaraju B et al, ".Net Interview Questions", 2010)

"The format of the data to be communicated and the logic under which it is created form the data contract. This contract is followed by both the producer and the consumer of the event data. It gives the event meaning and form beyond the context in which it is produced and extends the usability of the data to consumer applications." (Adam Bellemare, "Building Event-Driven Microservices", 2020)

"A data contract is a document that accompanies data movement and captures relevant information (like upstream contacts, service-level agreement, scenarios enabled, etc.)." (Vlad Riscutia, "Data Engineering on Azure", 2021)

"A data contract is a formal agreement between a service and a client that abstractly describes the data to be exchanged. That is, to communicate, the client and the service do not have to share the same types, only the same data contracts. A data contract precisely defines, for each parameter or return type, what data is serialized (turned into XML) to be exchanged." (Microsoft, "Using Data Contracts", 2021) [source]

"A data contract is a written agreement between the owner of a source system and the team ingesting data from that system for use in a data pipeline. The contract should state what data is being extracted, via what method (full, incremental), how often, as well as who (person, team) are the contacts for both the source system and the ingestion." (James Densmore, "Data Pipelines Pocket Reference", 2021)

"It's a formal agreement between the data producer and the data consumers. There is not yet a clear definition of the form and scope of a data contract. Usually, they cover the structure of the exchanged data (i.e. the schema) and its meaning (i.e. the semantics)." (Open Data Mesh, "Data Contract", 2022) [source]

"A data contract is an agreed interface between the generators of data and its consumers. It sets the expectations around that data, defines how it should be governed, and facilitates the explicit generation of quality data that meets the business requirements." (Andrew Jones, "Driving Data Quality with Data Contracts", 2023)

"A data contract is an agreement between the producer and the consumers of a data product. Just as business contracts hold up obligations between suppliers and consumers of a business product, data contracts define and enforce the functionality, manageability, and reliability of data products." (Atlan, "Data Contracts: The Key to Scaling Distributed Data Architecture and Reducing Data Chaos", 2023) [source]

"Data contracts are formal agreements outlining the structure and type of data exchanged between systems, ensuring all parties understand the data's format. Used in various contexts such as APIs, SOA, data pipelines, they provide crucial interoperability, making data contracts essential in managing and controlling data flow effectively." (Jatin Solanki, "What is Data Contracts, is it a hype?", 2023) [source]

"A formal agreement between a data consumer or user and a data provider or owner that defines the conditions under which the data is exchanged between both parties." (Circ Thread)

OOP: Contract (Definitions)

"A guarantee between a definer and a user. An example of a contract is the methods in an interface type. In adding the interface type to its definition, a type agrees to the contract specified by the interface type. Contracts vary from strictly enforceable, such as verifying that a function's signature conforms to a contract (syntax correctness), to assuming consistent behavior among classes implementing a common contract (semantic correctness). Semantic contracts are more difficult to specify and verify." (Damien Watkins et al, "Programming in the .NET Environment", 2002) 

[design by contract] "A paradigm stating that each software element (e.g., a method) specifies in a contract the pre-conditions it requires to run, the post-conditions it will ensure upon completion, and which invariants will remain." (Johannes Link & Peter Fröhlich, "Unit Testing in Java", 2003)

"Defines the responsibilities and postconditions that apply to the use of an operation or method. Also used to refer to the set of all conditions related to an interface." (Craig Larman, "Applying UML and Patterns", 2004)

"A service is usually described by an interface. The complete description of a service from a consumer’s point of view (signature and semantics) is called a 'well-defined interface' or contract." (Nicolai M Josuttis, "SOA in Practice", 2007)

"The complete description of a service interface between one consumer and one provider. It includes the technical interface (signature), the semantics, and nonfunctional aspects such as service-level agreements." (Nicolai M Josuttis, "SOA in Practice", 2007)

"A statement by the developer of a component about what the component does; users of the component rely on this statement to design systems using the component." (W Roy Schulte & K Chandy, "Event Processing: Designing IT Systems for Agile Companies", 2009)

"The protocol and requirements that exist between a module (e.g., class, trait, object, or even function or method) and clients of the module. More specifically, see Design by Contract." (Dean Wampler & Alex Payne, "Programming Scala", 2009)

[data contract:] "In WCF, a data contract is one that permits the definition of messages with multiple parameters." (Bruce Bukovics, "Pro WF: Windows Workflow in .NET 4", 2010)

[design by contract] "An approach to class and module design invented by Bertrand Meyer for the Eiffel language. For each entry point, valid inputs are specified in a programmatic way, so they can be validated during testing. These specifications are called preconditions. Similarly, assuming the preconditions are specified, specifications on the guaranteed results are called postconditions and are also specified in an executable way. Invariants can also be specified that should be true on entry and on exit." (Dean Wampler & Alex Payne, "Programming Scala", 2009)