computer science

OPC Historical Data Access

OPC Historical Data Access is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand OPC Historical Data Access rather than just read about it. In short: This group of standards, created by the OPC Foundation, provides COM specifications for communicating data from devices and applications that provide historical data, such as databases. The specifications provides for access to raw, interpolated and aggregate data (data with calculations).

Key takeaways

OPC Historical Data Access belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect OPC Historical Data Access to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of OPC Historical Data Access from memory before moving on to harder problems.

Reference excerpt

This group of standards, created by the OPC Foundation, provides COM specifications for communicating data from devices and applications that provide historical data, such as databases. The specifications provides for access to raw, interpolated and aggregate data (data with calculations). OPC Historical Data Access, also known as OPC HDA, is used to exchange archived process data. This is in contrast to the OPC Data Access (OPC DA) specification that deals with real-time data. OPC technology is based on client / server architecture. Therefore, an OPC client, such as a trending application or spreadsheet, can retrieve data from an OPC compliant data source, such as a historian, using OPC HDA. Similar to the OPC Data Access specification, OPC Historical Data Access also uses Microsoft's DCOM to transport data. DCOM also provides OPC HDA with full security features such as user authentication and authorization, as well as communication encryption services. OPC HDA Clients and Servers can reside on separate PCs, even if they are separated by a firewall. To do this, system integrators must configure DCOM properly as well as open ports in the firewall. If using the Windows firewall, users only need to open a single port.

See also OLE for process control OPC Foundation OPC Data Access

References

External links OPC Foundation OPC Historical Data Access specification

Worked examples

Example 1 — a first encounter with OPC Historical Data Access

Start with the simplest possible case. Write down what OPC Historical Data Access claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to OPC Historical Data Access before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about OPC Historical Data Access ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of OPC Historical Data Access

In research: OPC Historical Data Access appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses OPC Historical Data Access in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: OPC Historical Data Access is common in secondary-school and first-year university syllabi. It links to neighbouring topics Component-based software engineering, Computer standards, Industrial automation, so understanding it makes those chapters shorter.
In everyday life: Look for OPC Historical Data Access outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study OPC Historical Data Access in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what OPC Historical Data Access means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain OPC Historical Data Access out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is OPC Historical Data Access in simple terms?

Why does OPC Historical Data Access matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study OPC Historical Data Access?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on OPC Historical Data Access.