POSC Specifications
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Glossary
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Glossary
Index
Terms
- activity
- Something that happens bringing about change to the perceived state of the universe.
- absent value
- An attribute value that is undefined (from RP66). The equivalent terms are "indeterminate" in EXPRESS and "NULL" in SQL.
- aggregate type
- The supertype of the data types: bag, set, list, array, unique list and unique array. Ordered or unordered collections of data elements of a single simple type. See also bag type, set type, list type, array type. From EXPRESS.
- aggregate value
- A data value of aggregate type. The aggregate types are array, bag, list or set. See data type.
- angle type
- Plane angle, represented either as a decimal number and an angle unit or as degrees, minutes and seconds.
- American National Standards Institute
- An organizational body that defines and disseminates standards, including computing standards, in the United States.
- American Petroleum Institute
- An organizational body that, among other activities, disseminates information and defines standards for the oil and gas industry.
- ANSI
- Acronym for American National Standards Institute.
- anyquantity type
- An Epicentre data type that represents a measured quantity as a real number, a unit of measure and a reference to a quantity type, which constrains the valid units of measure.
- API
- Abbreviation for application programming interface. In this context, it usually means the POSC data access and exchange application programming interface.
- Abbreviation for the American Petroleum Institute.
- application
- Computer software that performs useful work for a user. Applications are considered architecturally above the level of the data access and exchange application programming interface. Synonyms: application program or application software.
- application programming interface
- A well-defined and documented (with respect to interface and behavior) set of computer program modules allowing applications to access some shareable resource or commonly needed function.
- array type
- An aggregate type whose instances are of fixed size and ordered. An array type may be defined as optional, meaning not all elements are required to have values in a particular instance. An array type may also require that all elements within an instance be unique. From EXPRESS.
- attribute
- A specific name for a type of information or data associated with an entity. (In RP66 the attribute is associated with an object.)
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- Backus-Naur form
- A formalized, general-purpose language used for defining the syntax of, usually computer, languages. Also Backus Normal Form.
- Backus Normal form
- Backus-Naur form.
- bag type
- A subtype of aggregate type representing an unordered collection of possibly repeating elements. See also aggregate type and type. From EXPRESS.
- binary type
- A subtype of an EXPRESS simple type defining a sequence of bits (of value zero or one) of fixed or variable width.
- BNF
- Acronym for Backus-Naur Form.
- boolean type
- A subtype of the EXPRESS simple type that is the set of the values TRUE and FALSE and where FALSE < TRUE. From EXPRESS.
- branding
- A contract between a software product vendor and POSC whereby both parties fulfill their obligations, which may include a product-certification process.
- business object
- A representation of a thing active in the business domain, including at least its business name and definition, attributes, behavior, relationship and constraints. A business object may represent, for example, a person, place or concept.
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- CAD
- Acronym for Computer-Aided Design.
- CAD Framework Initiative
- CAD industry-sponsored standards consortium.
- call interface
- The set of functions that implements an application programming interface.
- cardinality
- The number of elements in an item of interest not including null values.
- casting
- The mapping of an internal data type to an external data type or vice versa. Casting allows a data type to be used as some other type as long as such a mapping exists. See internal and external data types.
- CFI
- Abbreviation for CAD Framework Initiative.
- class rule
- This rule specifies how a supertype and its subtypes are created. A supertype entity may be abstract (cannot be created without at least one subtype being created) or nonabstract (can be created without being specialized to be any of its subtypes). The rule also describes whether one or more of a specified set of subclasses may be included in the instance.
- clause
- A fragment of a data access language query that conveys semantic meaning but does not constitute a complete language statement.
- collection type
- Synonym for aggregate type.
- common business object
- An entity, defined at a higher level of abstraction than an Epicentre entity, which has a specific and widespread general business purpose (see business object).
- compatibility layer
- An implementation of the POSC DAE built on a relational database management system in such a way that logical queries can be made against the database through the DAE or SQL queires can be made directly against the database.
- complex data type
- A data type defined in terms of simple types and/or other complex data types.
- complex type
- A complex number consisting of real and imaginary parts.
- complex value
- A data value of complex data type.
- compliance testing
- A process that measures a set of indicators of compliance.
- component
- The basic syntactic unit of an Explicitly Formatted Logical Record (EFLR). A Component consists of a Component Descriptor (one byte), followed by zero or more fields that contain characteristics associated with a set, object, or attribute. (RP66)
- component descriptor
- The first byte of a component. It has a role field (bits 1-3), which specifies whether the component describes a set, object, or attribute, and a format field (bits 4-8), which indicate which characteristics of the thing described are present in the remainder of the component. (RP66)
- concurrent transactions
- Separate transactions that access the same data or schema and overlap in time. See transactions. From SQL-92.
- conformance testing
- Synonym of compliance testing. (Usage discontinued in August 1994)
- correlation name
- An alias for an entity, used in a data access language statement. Specified in a FROM clause, it is used to provide a shortened or otherwise more convenient name for the entity.
- cursor
- An application programming interface object that identifies a SELECT statement result, an ordering of the result and a position within that ordering.
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- DAE
- An abbreviation for data access and exchange.
- DAEF
- Abbreviation for data access and exchange facility.
- data access and exchange
- The component of the POSC software integration platform that specifies a programming interface for access to data.
- data access and exchange API
- The data access and exchange application programming interface.
- data access and exchange facility
- An implementation of the data access and exchange specification component of the POSC software integration platform. . (In the case of the POSC data access and exchange sample implementation, the facility's functionality is provided via a set of modules using an underlying database.)
- data access language
- A portion of the data access and exchange specification that provides a declarative language for instance handling, including retrieval and creation. Language execution functions are provided to bind program variables, submit language statements, and retrieve results.
- data collection
- Data collections enable groups of entity instances to be defined. The purpose is to keep records of groups of data with the data items that constitute the record.
- data container
- In this context, a generic structure holding a set of references to instances.
- data model
- A description of the perceived data and relationships required for a business activity. A number of methodologies are used to define data models. Many include diagrams and definitions. One descriptive classification of data models is:
- Conceptual - a business representation independent of specific processing requirements and specific database management systems.
- Logical - a complete representation able to support actual processing needs. The logical model is independent of any specific database management system. A full logical data model includes detailed attribute characteristics such as instance identification, field lengths, data types, validity bounds, etc. (Epicentre is a logical data model.)
- Physical - a representation of the implementation of a data model for a specific database management system capable of supporting actual application software.
- data model dictionary
- The application-accessible description of the schema of a POSC data store accessed through the data access and exchange application programming interface.
- data modeling case tool
- Software supporting the definition and maintenance of data models.
- data scope
- The context in which operations defined by the application programming interface may be performed. Currently, the defined scopes are: data store, data collection and exchange set.
- data store
- Abbreviation of the phrase "POSC data store".
- data type
- A data value format and range specification. Data types are: simple, aggregate and Epicentre. See also simple type, aggregate type and Epicentre data type.
- date type
- A calendar date, specifying year, month and date.
- daytimeinterval type
- A time interval in any of days, hours, minutes, and seconds. Maximum number of days is 99999.
- DDL
- Abbreviation of the phrase "data definition language". DDL refers to the set of language statements a database management system uses to create, alter and delete data storage structures (tables). DDL commands are also used to manage user privileges and other system administrative tasks.
- deadlock
- A phenomenon in which two or more concurrent transactions wait for the release of a lock held by some other transaction, causing all the transactions to wait. Since each transaction is waiting, none can release the lock it holds.
- defined type
- A defined type is an EXPRESS-defined type, as established by the EXPRESS TYPE declaration. Associates a meaning with a data type. A defined type has a name and a data type. Defined type names are unique within the schema in which they appear.
- descriptor
- A data structure, defined by the application programming interface, which contains descriptive information about some item of interest, usually information allowing access to the elements of some list.
- direct manipulation calls
- A set of application programming interface functions for use by applications for instance handling, including retrieval and creation.
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- element subsetting
- Creating a subset by removing elements from the inclusive set. In terms of Epicentre, this equates to removing entities and optional attributes from the full model to achieve a subset model.
- element type
- A set of values for a specified set of property types for all instances of a selected element type of a selected grid or mesh. The property value arrays are numbered in accordance with the mesh or grid, and all element instances of the type may be given in values.
- entity
- An entity is a data model concept that represents a class of tangible or intangible real world things where all members of the class are given the same characterization, i.e., the same attributes and constraints.
- Epicentre
- The data model of the exploration and production industry developed at POSC. A logical data model, Epicentre is expressed in a form meaningful to the way petroleum application programs and professionals define and use data. Epicentre contains syntactic and semantic definitions. Syntactic definitions include identification, definition, and format of data; semantic definitions include business rules that apply to data, i.e., rules necessary to maintain a high level of data integrity and reliability.
- Epicentre data type
- An Epicentre data type has a well-defined structure, usually some specification parameters that constrain instances of the data type, and a declaration syntax. Epicentre data types include: date type, time type, timestamp type, yearmonthinterval type, daytimeinterval type, complex type, rational type, ratio type, quantity type, angle type, money type, location type, point type, line type, surface type, volume type, sample type, element type, and sparse type.
- Epigramme
- The POSC exchange format, with the model constrained to be the POSC Epicentre data model.
- event
- An asynchronous generation of a message caused by the change of state of some resource or process.
- event handling
- The invocation and execution, caused by an event, of a program module or modules.
- exchange file
- An RP66 logical file containing one or more exchange sets.
- exchange set
- A set of data to be encoded in the POSC exchange format.
- explicit attribute
- An attribute not derived from other attributes of the model.
- explicitly formatted logical record (EFLR)
- One of two logical records defined under RP66. The body of an EFLR is a sequence of components that combine to describe a single set of objects. An EFLR is self-describing and can be interpreted without the use or knowledge of any other logical records. (RP66)
- EXPRESS
- A formal information modeling language (ISO DIS 10303-11).
- EXPRESS to DDL compiler
- A computer program used to create the POSC data store for the sample implementation. It is a compiler that produces data definition language statements for some underlying database.
- extensibility
- The ability to expand or enlarge the scope, functionality or definition of something.
- external data type
- The type associated with a given attribute defined by a C program that accesses the attribute value through the application programming interface. This is not necessarily the same as the data type defined by Epicentre (see internal data type), but it must be mappable to some internal type (see casting).
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- foreign key
- A type of table column that contains the primary or secondary key of another row representing a relationship.
- functional subsetting
- Creating a subset by constraining characteristics of elements of the inclusive set. In terms of Epicentre, this involves constraining the cardinality of relationships and/or the allowed population of instances in an entity (see population subsetting).
- function
- Computer program context: A named encapsulation of program computation. A function has zero or more specified inputs and zero or more specified outputs. The computation part of the function maps the inputs to the outputs.
- Data access language context: A named encapsulation of data access functionality that maps an expression to a value. Normally, the input expression can be a constant value, attribute name, an arithmetic expression involving constants and attributes, or, most generally, an arithmetic expression involving constants, attributes and functions. A function may map attribute values (or expressions involving them) one-to-one to output values or map a set of tabulated values to an output value.
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- global rule
- Global rules constrain a set of unrelated entity instances. A global rule is not linked to any particular entity and can apply whenever required. Application of a global rule does not change instance value; it checks for consistency with the constraint. From EXPRESS.
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- handle
- A value that unambiguously identifies an object of interest to an application program. In some cases it may be a pointer to some region of application memory, in other cases it may refer to an object in a data store. Handles are used for reference only. They are never operated on by the application.
- high bound
- The maximum number of instances allowed for a bag, list or set aggregate type. From EXPRESS.
- high index number
- This is the maximum value of the index of an ARRAY type of COLLECTION STRUCTURE.
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- Indirectly Formatted Logical Record (IFLR)
- One of two kinds of logical record defined under RP66. The body of an IFLR consists of a data descriptor reference, followed by an arbitrary number of bytes of indirectly formatted data. This data is not self-descriptive. Its format is determined from information contained in the object named by the data descriptor reference and possibly related objects. For example, the format of a frame data IFLR is specified by a frame object and by one or more channel objects referenced by the frame object. (RP66)
- inheritance
- A modeling construct and mechanism whereby entities can make use of the characteristics defined in their respective supertypes. Inheritance is defined in the EXPRESS language.
- instance
- A collection of attribute values that represents a real-world thing as intended by the data model. Such an instance might be represented within an exchange set by an object in an EFLR or a frame in an IFLR.
- instantiate
- To create an instance of an entity. See instance and entity.
- integer type
- An integer type is one whose domain is the integer numbers or a subset thereof.
internal data type
The type associated with a given attribute defined by Epicentre and bound to a given data store.
- International Organization for Standardization
- A worldwide federation of national standards institutes. The work of developing international standards is carried out by ISO technical committees. Every member body interested in a subject for which a technical committee has been set up has the right to be represented on that committee.
- interoperable
- Able to integrate elements from diverse sources into a coherent whole. In this context, interoperability refers to the ability to integrate application programs from different application systems, disciplines, computing environments, and/or vendors to work effectively together.
- ISO
- Abbreviation for International Organization for Standardization.
- isolation level
- The degree to which operations on data by a transaction are affected by concurrent transactions. Also, the degree to which operations on data by a transaction can affect data in concurrent transactions.
- iterate
- To repeat once for each element in a collection.
- iterator
- A mechanism for accessing the values of an aggregate type or list of items.
- inverse attribute
- An attribute whose value is dependent on an explicit attribute. From EXPRESS.
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- keyword
- One of an enumerated set of symbols or tokens, which are words in the data access language, used for syntactic definition and to convey semantic meaning.
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- language
- In the context of the data access and exchange specification, short for data access language.
- language binding
- A specification of an application programming interface or program module as called in a particular programming language.
- levels of specification
- Subsets of the specification, determined by the methods used for handling instances.
- library
- A set of computer software modules providing services to applications. Libraries are considered architectural peers to the POSC data access and exchange facility. See toolkit.
- line type
- A continuous line described in a specific coordinate system. The line values are described using a one-dimensional grid, which may be specified using an arbitrary parameter or using a variable of a coordinate system.
- list type
- An aggregate type whose instances are ordered and the number of instances may vary between the lower and upper bounds. From EXPRESS.
- location type
- A coordinate point in a particular coordinate system. The point coordinates may be specified relative to a vertex entity specified as part of the point instance.
- logical type
- A subtype of simple type that is the set of the values TRUE, FALSE and UNKNOWN and where FALSE < UNKNOWN < TRUE. From EXPRESS.
- logical file
- A sequence of two or more contiguous logical records in a storage set that begins with a file header logical record and contains no other file header logical records. A logical file must have at least one OLR (Origin) Logical Record immediately following the file header logical record. A logical file supports user-level organization of data. (RP66)
- logical format
- The view of RP66 data independent of any physical mapping. The RP66 logical format consists of a sequence of logical records organized into one or more logical files. This format is the same for any physical representation of the data. (RP66)
- logical record
- Forms the basic coherent body of information in RP66. Logical records encapsulate semantically related information.
- long transaction
- A transaction that may span multiple sessions and whose method of concurrency control is check-out and check-in.
- low bound
- The minimum number of instances within a BAG, LIST or SET aggregate type. From EXPRESS.
- low index number
- This is the minimum value of the index of an ARRAY aggregate type. From EXPRESS.
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- mapping
- In this context, mapping stands for model mapping. It defines the similarity and differences between two data models. The mapping specifies the transition of the data from an initial data structure to a final data structure.
- memory management
- The programming practices associated with making computer memory available to an application (memory allocation) and freeing the memory when not needed (freeing or deallocation).
- message
- A package of information sent from one application or process to another or to itself.
- method
- In this specification, an operation defined on an entity or domain.
- money type
- An amount of a specific currency.
- multicast message server
- A computer process that receives messages from other processes, then sends or otherwise makes those messages available to other registered processes.
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- named defined type
- A named defined type is a use of an underlying data type that is given a particular name. Use of a named defined type is similar to use of domains in conventional methodologies, except Epicentre Data Types define some new aggregate domain structures. Refers to a usage of a defined type that does not reference entity definitions.
- natural identifier
- POSC synonym for "secondary identifier".
- NDT
- Abbreviation for named defined type.
- non-null
- An adjective applied to attributes, values or variables specifying that the associated value is known.
- non-terminal symbol
- A symbol used in a BNF language description rule, appearing on the left side of some rule in the description. Non-terminal symbols can be expanded into a sequence of terminal symbols.
- null
- An adjective applied to attributes, values or variables specifying that the associated value is not known. Corresponds to the EXPRESS term "indeterminate".
- number type
- A simple type that is the domain of all numbers. The supertype of the real type and the integer type. From EXPRESS.
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- object
- 1. A thing (either tangible or an abstract concept) which is of interest to the E&P industry. 2. A data item having a name and a number of attributes. An object is similar to an entity. Objects are recorded in EFLRs (in RP66).
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- parse
- To analyze a stream of words or a sentence for syntactic correctness and to organize those words according to the rules of a grammar associated with a language.
- PDS
- Abbreviation for POSC data store.
- PEF
- Abbreviation for POSC exchange format.
- persistence
- That quality of an instance of data related to its existence beyond and outside of the life of its creating process or the lives of other processes that use it. In this context, persistence is normally used in describing the life of objects relative to sessions, i.e., whether or not they live beyond sessions.
- Petrotechnical Open Software Corporation
- A not-for-profit membership corporation dedicated to defining an open computing environment termed the software integration platform. Developed for technical applications in the international oil and gas exploration and production industry, the software integration platform is a set of specifications that addresses:
- Base computing environment
- Management of data and information
- Access to data by applications
- Exchange of data
- User interface
The goal of these specifications is to provide methods for oil and gas organizations to manage data resources and support integrated multi-disciplinary projects.
- physical implementation
- The manifestation of a logical or conceptual model in an actual data store in a computer system.
- point type
- A point described by coordinates of a coordinate system with zero or more property values, where each property may be evaluated on a coordinate system axis. The point coordinates may be specified relative to a vertex entity specified as part of the point instance.
- population subsetting
- Creating a model subset by constraining the allowed population of instances in the subset's entities. This is a type of functional subsetting.
- pointer
- A program variable containing the memory address of a (normally different) program variable.
- portability
- The ability of a given piece of software to be moved from one computing platform to another. In most cases, portability is at the source code level because machines with different architectures require such code to be, at a minimum, recompiled and re-linked.
- POSC
- Acronym for Petrotechnical Open Software Corporation.
- POSC computing environment
- A service that coordinates various aspects of interactions of applications with an implementation of the POSC software integration platform.
- POSC data access and exchange layer
- A subset of an implementation of the data access and exchange facility, and linked to an underlying database. See sample implementation and underlying database.
- POSC data store
- A collection of instances, administered together, conforming to a single version of Epicentre and managed by an installed data access and exchange facility.
- POSC exchange format (PEF)
- The generic data format defined by POSC to support the external exchange of data by application programs. Any data that conforms to Epicentre may be represented in this format.
- POSC exchange format file
- A computer-readable file of data conforming to the specifications of the POSC exchange format. An exchange format file may exist in computer memory or on storage media such as magnetic tape or disc.
- POSC Epicentre meta model
- The Epicentre meta model defines the types and meanings of Epicentre data. The meta model forms the basis of the methodology and the data access layer. The Epicentre meta model is specified in EXPRESS and includes many concepts of the EXPRESS Language.
- predicate
- A boolean-valued phrase used within a WHERE clause of a data access language statement to restrict the instances acted upon or returned by the statement.
- process
- An environment created by a computer's operating system or kernel in which a computer program (i.e. application) executes.
- production rule
- A definition of a nonterminal symbol, used in a BNF description of the syntax of a language, of the legal combinations of terminal and nonterminal symbols that can be represented by the nonterminal symbol.
- primary key
- A relational table column type, containing a system or machine generated identifier of the row. Primary key values may be duplicated as foreign keys to represent relationships.
- projection
- The process of transforming a logical data model into the DDL statements required to construct
a physical data store consistent with the logical model.
In Version 2.2 of Epicentre, POSC projected Epicentre into four variations of SQL DDL.
The POSC projection process also creates a set of meta data which is used to tie the
resulting SQL tables and columns to the Epicentre entities and attributes they are derived from.
- property
- A characteristic of an object for which there may be several values corresponding to the results of different activities.
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- quantity type
- An Epicentre data type representing a quantity as a real number and a unit of measure. The unit of measure is constrained to be one of a set of alternative units of measure specified by the type use declarations.
- query
- An application programming interface usage intended to access (retrieve, create, update or delete) data. A query may be made with a direct manipulation interface call or with a language execution interface call.
- A direct manipulation FindInstance call or a data access language SELECT statement.
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- ratio type
- A ratio expressed as a real number numerator and a real number denominator.
- rational type
- A rational number expressed as an integer numerator and an integer denominator.
- real type
- A type whose domain is the real numbers or a subset thereof. It may specify a required precision for elements of the type.
- recoverable subset
- A subset of Epicentre from which data can be extracted, moved to the full Epicentre model and back to the subset again without loss of semantics. First used by the POSC Project Work Order Team in 1995. See also uploadable subset.
- reference behavior
- Entities having a reference behavior may have standard instances predefined. They differ from reference entities because only some of their attributes may be predefined. The population of the missing attributes may be added later.
- reference entity
- An entity for which POSC provides standard instances. Reference entities differ from other entities in that some standard instance values have been declared, either by POSC or by other organizations
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- related instance rule
- A related instance rule constrains the instantiation of related entity instances where alternative relationship paths lead to the same entity.
- relationship
- A binary, ordered association of an entity with itself or between two entities.
- representation code
- Each distinct piece of information in the logical format has a well-defined representation extending across one or more bytes. Each different representation is identified by a one-byte representation code. Representation codes are defined in RP66, Appendix B, and identify the various floating-point, integer, and text representations permitted in RP66. (RP66)
- request
- A reference to a DAEF function by a 3GL program.
- RP66
- American Petroleum Institute Recommended Practice 66. An alternative title of the RP66 specification is Digital Log Interchange Standard (DLIS). In another common usage, the term DLIS refers to the schemas, semantics, and codes specific to well logs, and RP66 refers to the syntax and the general-purpose schemas and codes.
- rule
- A constraint on existence and/or value affecting one or more instances. EXPRESS defines local and global rules.
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- sample implementation
- POSC's realization of a software integration platform component.
- savepoint
- A point within a transaction after which all effects on the data by the transaction may be reversed.
- scalability
- The ability of applications to run on a wide range of hardware, from a desktop workstation to a supercomputer, with a minimum of modifications.
- schema
- A persistent descriptor that contains the description for every entity, rule, trigger, attribute, method, user-defined data type and any other objects in a POSC data store. Also, the systematic and organized framework of entities and their relationships, defining a universe of discourse in which the entities have related meaning and purpose.
- secondary identifier
- A group of entity characteristics commonly used by people to distinguish occurrences of real world things. A column type which contains real world information, constrained to be unique within the rows of the table.
- select rule
- A rule which constrains the instantiation of a set of attributes of an entity.
- session
- The time interval of an application process during which there is a connection to a data access computing environment. During a session, the application programming interface may be used to access and update data in one or more data stores.
- set type
- A subtype of aggregate type representing an unordered collection of elements in which no two or more elements are the same. See also aggregate type and type. From EXPRESS.
- short transaction
- A transaction guaranteed to occur wholly within one session and whose mechanism of concurrency control is read and write locks.
- simple type
- An unstructured, built-in type in EXPRESS. Also see integer type, real type, string type, binary type, logical type, and boolean type.
- SIP
- Acronym for software integration platform.
- SIP implementation
- A conforming and operational realization of the software integration platform specifications. See software integration platform.
- software integration platform
- A set of specifications defining the interfaces between a petrotechnical application and its environment, which consists of data, computer hardware/software facilities, and users. The software integration platform is the complete set of POSC specifications. See SIP implementation.
- sparse type
- A set of property values for a specified set of property types for specified instances of a selected element type of a selected grid or mesh. The property values are identified in accordance with the chosen mesh or grid.
- specialization
- A redeclaration of the defined type of an inherited attribute, where the new defined type is more constraining.
- SQL
- An acronym for Structured Query Language. SQL is a generic name applied to many dialects and extensions of a relational database query and manipulation language developed by IBM Corp. in 1974.
- SQL1
- The database language defined by SQL-89. See SQL-89.
- SQL2
- The database language defined by SQL-92. See SQL-92.
- SQL3
- A database language under development as a standard by ANSI committee X3H2. SQL3 is intended to be the successor to SQL2. See SQL-92.
- SQL-89
- The standard developed by ANSI Committee X3H2 and specified in ANSI document number X3.135-1989 and entitled Database Language - SQL with Integrity Enhancement. A parallel international standard is ISO Standard ISO/IEC 9075:1989 entitled Database Language SQL. The language of these standards is informally known as SQL1. SQL-92 cancels and replaces SQL-89. See SQL-92.
- SQL-92
- The standard developed by ANSI Committee X3H2 and specified in ANSI document number X3.135-1992 and entitled Database Language SQL. A parallel, identical, international standard is ISO Standard ISO/IEC 9075:1992 entitled Database Language SQL. The language of these standards is informally known as SQL2. SQL-92 cancels and replaces SQL-89.
- SQL-92 EL
- The entry level standard for SQL-92.
- standard unique identifier
- A universally unique, persistent instance identifier. An SUI unambiguously identifies an instance of an entity in any POSC data store or POSC exchange format file.
- state
- One of the complete set of conditions of an object, characterized by the values of system variables and expected input to the system.
- state transition
- A change of state of an object.
- string type
- A type whose domain is a set of similarly sized string literals.
- subclass
- A term used in previous documents. Replaced by subtype.
- subquery
- A SELECT statement appearing within another data access language statement. A subquery is usually subject to some behavior restrictions, as compared to a SELECT statement, because of its use within another statement.
- subtype
- An entity defined in terms of one or more different entities via the mechanism of inheritance. An entity from which a subtype inherits is called a supertype of the entity. See inheritance.
- SUI
- Acronym for Standard Unique Identifier.
- superclass
- A term used in previous documents. Replaced by supertype.
- supertype
- A data type having a subtype. See subtype.
- supertype rule
- Controls the instantiation of a supertype domain and its subtypes. Domains may be abstract or nonabstract and their subtypes can be created in conjunction with the supertype singly (i.e.,only one of) or in combination (i.e., and or).
- syntax
- The complete set of rules specifying all the correct sequences of tokens in a language.
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- template
- A sequence of attributes at the beginning of a set that specifies defaults for the objects in the set. Attributes in the template must have labels. Objects in the set have no attributes other than those identified in the template.
- terminal
- Same as terminal symbol.
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- terminal symbol
- A symbol used in a BNF language description rule that does not appear on the left side of any rule in the description. Terminal symbols are the keywords, reserved words or values that comprise a statement.
- test suite
- A program to test the behavior of a vendor product or to check the syntax of the source code for compliance with a specification.
- time type
- A clock time specifying hour within day, minutes and seconds.
- timestamp type
- A clock time specifying year, month, and day values of a date as well as the hour, minute, and second values.
- token
- An indivisible lexical unit of a language consisting of one or more characters in sequence, containing no whitespace characters and with an associated meaning. The tokens of a language are also the terminal symbols of the BNF description of the language. See also terminal symbol.
- toolkit
- A set of computer software modules providing services to applications. Toolkits are considered architectural peers to the POSC data access and exchange facility. See library.
- topic
- A topic is a POSC classification of related entities in Epicentre.
- transaction
- A single execution of a sequence of calls accessing a data store, guaranteed by the system to occur in its entirety or not at all. A transaction by this definition is also known as an atomic transaction or a transaction that is atomic with respect to recovery. From SQL-92.
- trigger
- A procedure stored with a data store and associated with an entity and executed whenever a pre-specified condition relating to the entity occurs, such as when an attribute value exceeds a limit or an instance is deleted.
- tuple type
- A data type representing an ordered collection of elements of different data type and entity instance references.
- type
- Same as data type.
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- underlying database
- Potentially, though not necessarily, a specific database management system that can be used to provide services to a data access and exchange facility.
- unique array type
- A subtype of aggregate type. An aggregate type representing an ordered, collection of elements which can be indexed and in which no two or more elements are the same. See also aggregate type and type.
- unique list type
- A subtype of aggregate type. An aggregate type representing an ordered collection of elements in which no two or more elements are the same. See also aggregate type and type.
- uniqueness rule
- A rule specifying a combination of attributes whose values, when taken jointly, uniquely identify a single instance of the declaring entity.
- uploadable subset
- A subset of Epicentre from which data can be extracted, moved to the full Epicentre model and back to the subset again without loss of semantics. This term is more descriptive of the intended function than the term recoverable subset, first used by the POSC Project Work Order Team in 1995.
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- validation suite
- A test suite that tests the behavior of a product with respect to a reference.
- value container
- A generic structure for communicating values between the application programming interface and the application that contains information about the value such as its type, size and location in the memory space of the application.
- value rule
- A value rule has no predetermined semantics or descriptions. It is described in the Epicentre specification using unstructured text and is defined using EXPRESS syntax. Its scope is limited to the scope of EXPRESS local rules.
- variable binding
- A technique of moving data between an application and a data access and exchange facility in which the facility and the application share program memory.
- view
- A subset of Epicentre. A view is represented by a diagram showing the entities and relationships within the model relevant to a particular aspect of the business.
- volume type
- A continuous three dimensional space described in a specific coordinate system. The volume is specified using a regularly connected three-dimensional grid. This may be defined parametrically using i, j, k or by assigning each grid dimension to three coordinate system variables.
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- where rule
- Where rules are used to define further constraints on the instance values. Three general types of where rules are defined for Epicentre corresponding to commonly occurring requirements. These are: Select rules, Related Instance Rules, and Value rules.
- work environment
- A computing environment consisting of hardware, system software, application software, data, and users. A work environment supports administrative activities, such as installation, user registration, data store creation, etc., and dynamic activities, such as sessions and transactions.
- working set
- A nonpersistent (i.e., process-bound) representation of a data collection. For a working set to become persistent it may be stored in an Epicentre data store as an instance of a data collection.
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- yearmonthinterval type
- An interval between two dates, given in years and months.
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